diff --git a/libavformat/aacdec.c b/libavformat/aacdec.c
index fecb1e381d..5ab5197e33 100644
--- a/libavformat/aacdec.c
+++ b/libavformat/aacdec.c
@@ -89,7 +89,7 @@ static int adts_aac_read_header(AVFormatContext *s)
     st->need_parsing         = AVSTREAM_PARSE_FULL_RAW;
 
     ff_id3v1_read(s);
-    if (s->pb->seekable &&
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
         !av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
         int64_t cur = avio_tell(s->pb);
         ff_ape_parse_tag(s);
diff --git a/libavformat/adp.c b/libavformat/adp.c
index 9ab2ec4566..735550307e 100644
--- a/libavformat/adp.c
+++ b/libavformat/adp.c
@@ -59,7 +59,7 @@ static int adp_read_header(AVFormatContext *s)
     st->codecpar->channels       = 2;
     st->codecpar->sample_rate    = 48000;
     st->start_time            = 0;
-    if (s->pb->seekable)
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)
         st->duration          = av_get_audio_frame_duration2(st->codecpar, avio_size(s->pb));
 
     avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
index 3bbe4a07bd..7dcc85f1ed 100644
--- a/libavformat/aiffdec.c
+++ b/libavformat/aiffdec.c
@@ -288,9 +288,9 @@ static int aiff_read_header(AVFormatContext *s)
             offset = avio_rb32(pb);      /* Offset of sound data */
             avio_rb32(pb);               /* BlockSize... don't care */
             offset += avio_tell(pb);    /* Compute absolute data offset */
-            if (st->codecpar->block_align && !pb->seekable)    /* Assume COMM already parsed */
+            if (st->codecpar->block_align && !(pb->seekable & AVIO_SEEKABLE_NORMAL))    /* Assume COMM already parsed */
                 goto got_sound;
-            if (!pb->seekable) {
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
                 av_log(s, AV_LOG_ERROR, "file is not seekable\n");
                 return -1;
             }
diff --git a/libavformat/aiffenc.c b/libavformat/aiffenc.c
index 74b778bbcb..fcadf149a0 100644
--- a/libavformat/aiffenc.c
+++ b/libavformat/aiffenc.c
@@ -49,7 +49,7 @@ static int put_id3v2_tags(AVFormatContext *s, AIFFOutputContext *aiff)
     AVIOContext *pb = s->pb;
     AVPacketList *pict_list = aiff->pict_list;
 
-    if (!pb->seekable)
+    if (!pb->seekable & AVIO_SEEKABLE_NORMAL)
         return 0;
 
     if (!s->metadata && !aiff->pict_list)
@@ -267,7 +267,7 @@ static int aiff_write_trailer(AVFormatContext *s)
         end_size++;
     }
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* Number of sample frames */
         avio_seek(pb, aiff->frames, SEEK_SET);
         avio_wb32(pb, (file_size - aiff->ssnd - 12) / par->block_align);
diff --git a/libavformat/ape.c b/libavformat/ape.c
index 061f32866f..50a1aa13c1 100644
--- a/libavformat/ape.c
+++ b/libavformat/ape.c
@@ -374,7 +374,7 @@ static int ape_read_header(AVFormatContext * s)
     }
 
     /* try to read APE tags */
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         ff_ape_parse_tag(s);
         avio_seek(pb, 0, SEEK_SET);
     }
diff --git a/libavformat/apngenc.c b/libavformat/apngenc.c
index 0c40be297f..378a9b3b36 100644
--- a/libavformat/apngenc.c
+++ b/libavformat/apngenc.c
@@ -258,7 +258,7 @@ static int apng_write_trailer(AVFormatContext *format_context)
 
     apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
 
-    if (apng->acTL_offset && io_context->seekable) {
+    if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {
         avio_seek(io_context, apng->acTL_offset, SEEK_SET);
 
         AV_WB32(buf, apng->frame_number);
diff --git a/libavformat/asfdec_o.c b/libavformat/asfdec_o.c
index 56f8446b5f..f7000b0413 100644
--- a/libavformat/asfdec_o.c
+++ b/libavformat/asfdec_o.c
@@ -960,7 +960,7 @@ static int asf_read_data(AVFormatContext *s, const GUIDParseTable *g)
                size, asf->nb_packets);
     avio_skip(pb, 2); // skip reserved field
     asf->first_packet_offset = avio_tell(pb);
-    if (pb->seekable && !(asf->b_flags & ASF_FLAG_BROADCAST))
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !(asf->b_flags & ASF_FLAG_BROADCAST))
         align_position(pb, asf->offset, asf->data_size);
 
     return 0;
@@ -1738,7 +1738,9 @@ static int asf_read_header(AVFormatContext *s)
             size = avio_rl64(pb);
             align_position(pb, asf->offset, size);
         }
-        if (asf->data_reached && (!pb->seekable || (asf->b_flags & ASF_FLAG_BROADCAST)))
+        if (asf->data_reached &&
+            (!(pb->seekable & AVIO_SEEKABLE_NORMAL) ||
+             (asf->b_flags & ASF_FLAG_BROADCAST)))
             break;
     }
 
@@ -1747,7 +1749,7 @@ static int asf_read_header(AVFormatContext *s)
         ret = AVERROR_INVALIDDATA;
         goto failed;
     }
-    if (pb->seekable)
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL)
         avio_seek(pb, asf->first_packet_offset, SEEK_SET);
 
     for (i = 0; i < asf->nb_streams; i++) {
diff --git a/libavformat/asfenc.c b/libavformat/asfenc.c
index 19dee3d528..1b67143afd 100644
--- a/libavformat/asfenc.c
+++ b/libavformat/asfenc.c
@@ -473,7 +473,7 @@ static int asf_write_header1(AVFormatContext *s, int64_t file_size,
     avio_wl64(pb, duration); /* end time stamp (in 100ns units) */
     avio_wl64(pb, asf->duration); /* duration (in 100ns units) */
     avio_wl64(pb, PREROLL_TIME); /* start time stamp */
-    avio_wl32(pb, (asf->is_streamed || !pb->seekable) ? 3 : 2);  /* ??? */
+    avio_wl32(pb, (asf->is_streamed || !(pb->seekable & AVIO_SEEKABLE_NORMAL)) ? 3 : 2);  /* ??? */
     avio_wl32(pb, s->packet_size); /* packet size */
     avio_wl32(pb, s->packet_size); /* packet size */
     avio_wl32(pb, bit_rate ? bit_rate : -1); /* Maximum data rate in bps */
@@ -530,7 +530,7 @@ static int asf_write_header1(AVFormatContext *s, int64_t file_size,
             avio_wl32(pb, 5000); /* maximum buffer size ms */
             avio_wl32(pb, 0); /* max initial buffer fullness */
             avio_wl32(pb, 0); /* max object size */
-            avio_wl32(pb, (!asf->is_streamed && pb->seekable) << 1); /* flags - seekable */
+            avio_wl32(pb, (!asf->is_streamed && (pb->seekable & AVIO_SEEKABLE_NORMAL)) << 1); /* flags - seekable */
             avio_wl16(pb, n + 1); /* stream number */
             avio_wl16(pb, asf->streams[n].stream_language_index); /* language id index */
             avio_wl64(pb, 0); /* avg time per frame */
@@ -1135,7 +1135,7 @@ static int asf_write_trailer(AVFormatContext *s)
     }
     avio_flush(s->pb);
 
-    if (asf->is_streamed || !s->pb->seekable) {
+    if (asf->is_streamed || !(s->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         put_chunk(s, 0x4524, 0, 0); /* end of stream */
     } else {
         /* rewrite an updated header */
diff --git a/libavformat/astenc.c b/libavformat/astenc.c
index 11f8717495..578e658891 100644
--- a/libavformat/astenc.c
+++ b/libavformat/astenc.c
@@ -139,7 +139,7 @@ static int ast_write_trailer(AVFormatContext *s)
 
     av_log(s, AV_LOG_DEBUG, "total samples: %"PRId64"\n", samples);
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* Number of samples */
         avio_seek(pb, ast->samples, SEEK_SET);
         avio_wb32(pb, samples);
diff --git a/libavformat/au.c b/libavformat/au.c
index f70f827201..520824fc12 100644
--- a/libavformat/au.c
+++ b/libavformat/au.c
@@ -321,7 +321,7 @@ static int au_write_trailer(AVFormatContext *s)
     AUContext *au = s->priv_data;
     int64_t file_size = avio_tell(pb);
 
-    if (s->pb->seekable && file_size < INT32_MAX) {
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && file_size < INT32_MAX) {
         /* update file size */
         avio_seek(pb, 8, SEEK_SET);
         avio_wb32(pb, (uint32_t)(file_size - au->header_size));
diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index abe8c988f1..e2527a1e31 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -948,7 +948,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
             break;
         case MKTAG('i', 'n', 'd', 'x'):
             pos = avio_tell(pb);
-            if (pb->seekable && !(s->flags & AVFMT_FLAG_IGNIDX) &&
+            if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !(s->flags & AVFMT_FLAG_IGNIDX) &&
                 avi->use_odml &&
                 read_odml_index(s, 0) < 0 &&
                 (s->error_recognition & AV_EF_EXPLODE))
@@ -1022,7 +1022,7 @@ fail:
         return AVERROR_INVALIDDATA;
     }
 
-    if (!avi->index_loaded && pb->seekable)
+    if (!avi->index_loaded && (pb->seekable & AVIO_SEEKABLE_NORMAL))
         avi_load_index(s);
     calculate_bitrate(s);
     avi->index_loaded    |= 1;
diff --git a/libavformat/avienc.c b/libavformat/avienc.c
index 4b042a92ad..91b8c40e32 100644
--- a/libavformat/avienc.c
+++ b/libavformat/avienc.c
@@ -332,7 +332,7 @@ static int avi_write_header(AVFormatContext *s)
         avio_wl32(pb, 0);
     avio_wl32(pb, bitrate / 8); /* XXX: not quite exact */
     avio_wl32(pb, 0); /* padding */
-    if (!pb->seekable)
+    if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
         avio_wl32(pb, AVIF_TRUSTCKTYPE | AVIF_ISINTERLEAVED);  /* flags */
     else
         avio_wl32(pb, AVIF_TRUSTCKTYPE | AVIF_HASINDEX | AVIF_ISINTERLEAVED);  /* flags */
@@ -414,7 +414,7 @@ static int avi_write_header(AVFormatContext *s)
         avio_wl32(pb, 0); /* start */
         /* remember this offset to fill later */
         avist->frames_hdr_strm = avio_tell(pb);
-        if (!pb->seekable)
+        if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
             /* FIXME: this may be broken, but who cares */
             avio_wl32(pb, AVI_MAX_RIFF_SIZE);
         else
@@ -493,7 +493,7 @@ static int avi_write_header(AVFormatContext *s)
             }
         }
 
-        if (pb->seekable) {
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
             write_odml_master(s, i);
         }
 
@@ -534,7 +534,7 @@ static int avi_write_header(AVFormatContext *s)
         ff_end_tag(pb, list2);
     }
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* AVI could become an OpenDML one, if it grows beyond 2Gb range */
         avi->odml_list = ff_start_tag(pb, "JUNK");
         ffio_wfourcc(pb, "odml");
@@ -611,7 +611,7 @@ static int avi_write_ix(AVFormatContext *s)
     char ix_tag[] = "ix00";
     int i, j;
 
-    av_assert0(pb->seekable);
+    av_assert0(pb->seekable & AVIO_SEEKABLE_NORMAL);
 
     for (i = 0; i < s->nb_streams; i++) {
         AVIStream *avist = s->streams[i]->priv_data;
@@ -669,7 +669,7 @@ static int avi_write_idx1(AVFormatContext *s)
     int i;
     char tag[5];
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         AVIStream *avist;
         AVIIentry *ie = 0, *tie;
         int empty, stream_id = -1;
@@ -783,7 +783,7 @@ static int avi_write_packet(AVFormatContext *s, AVPacket *pkt)
 
                 av_assert0(par->bits_per_coded_sample >= 0 && par->bits_per_coded_sample <= 8);
 
-                if (pb->seekable && avist->pal_offset) {
+                if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && avist->pal_offset) {
                     int64_t cur_offset = avio_tell(pb);
                     avio_seek(pb, avist->pal_offset, SEEK_SET);
                     for (i = 0; i < pal_size; i++) {
@@ -798,7 +798,7 @@ static int avi_write_packet(AVFormatContext *s, AVPacket *pkt)
                     unsigned char tag[5];
                     avi_stream2fourcc(tag, stream_index, par->codec_type);
                     tag[2] = 'p'; tag[3] = 'c';
-                    if (s->pb->seekable) {
+                    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
                         if (avist->strh_flags_offset) {
                             int64_t cur_offset = avio_tell(pb);
                             avio_seek(pb, avist->strh_flags_offset, SEEK_SET);
@@ -854,7 +854,7 @@ static int avi_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
     avist->packet_count++;
 
     // Make sure to put an OpenDML chunk when the file size exceeds the limits
-    if (pb->seekable &&
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) &&
         (avio_tell(pb) - avi->riff_start > AVI_MAX_RIFF_SIZE)) {
         avi_write_ix(s);
         ff_end_tag(pb, avi->movi_list);
@@ -872,7 +872,7 @@ static int avi_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
     if (par->codec_type == AVMEDIA_TYPE_AUDIO)
         avist->audio_strm_length += size;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int ret;
         ret = avi_add_ientry(s, stream_index, NULL, flags, size);
         if (ret < 0)
@@ -901,7 +901,7 @@ static int avi_write_trailer(AVFormatContext *s)
         write_skip_frames(s, i, avist->last_dts);
     }
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         if (avi->riff_id == 1) {
             ff_end_tag(pb, avi->movi_list);
             res = avi_write_idx1(s);
@@ -950,7 +950,7 @@ static int avi_write_trailer(AVFormatContext *s)
             av_freep(&avist->indexes.cluster[j]);
         av_freep(&avist->indexes.cluster);
         avist->indexes.ents_allocated = avist->indexes.entry = 0;
-        if (pb->seekable) {
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
             avio_seek(pb, avist->frames_hdr_strm + 4, SEEK_SET);
             avio_wl32(pb, avist->max_size);
         }
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 4ade4d0d7e..5f58ab064b 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -269,7 +269,7 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
         offset1 >= 0 && offset1 <= buffer_size - s->write_flag) {
         /* can do the seek inside the buffer */
         s->buf_ptr = s->buffer + offset1;
-    } else if ((!s->seekable ||
+    } else if ((!(s->seekable & AVIO_SEEKABLE_NORMAL) ||
                offset1 <= buffer_size + short_seek) &&
                !s->write_flag && offset1 >= 0 &&
                (!s->direct || !s->seek) &&
diff --git a/libavformat/bink.c b/libavformat/bink.c
index e6f0cb78ed..20dba677db 100644
--- a/libavformat/bink.c
+++ b/libavformat/bink.c
@@ -292,7 +292,7 @@ static int read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, in
     BinkDemuxContext *bink = s->priv_data;
     AVStream *vst = s->streams[0];
 
-    if (!s->pb->seekable)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return -1;
 
     /* seek to the first frame */
diff --git a/libavformat/bintext.c b/libavformat/bintext.c
index a264fd1b5f..12e3bfde4d 100644
--- a/libavformat/bintext.c
+++ b/libavformat/bintext.c
@@ -141,7 +141,7 @@ static int bintext_read_header(AVFormatContext *s)
     st->codecpar->extradata[0] = 16;
     st->codecpar->extradata[1] = 0;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int got_width = 0;
         bin->fsize = avio_size(pb);
         if (ff_sauce_read(s, &bin->fsize, &got_width, 0) < 0)
@@ -199,7 +199,7 @@ static int xbin_read_header(AVFormatContext *s)
     if (avio_read(pb, st->codecpar->extradata + 2, st->codecpar->extradata_size - 2) < 0)
         return AVERROR(EIO);
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         bin->fsize = avio_size(pb) - 9 - st->codecpar->extradata_size;
         ff_sauce_read(s, &bin->fsize, NULL, 0);
         avio_seek(pb, 9 + st->codecpar->extradata_size, SEEK_SET);
@@ -237,7 +237,7 @@ static int adf_read_header(AVFormatContext *s)
     if (avio_read(pb, st->codecpar->extradata + 2 + 48, 4096) < 0)
         return AVERROR(EIO);
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int got_width = 0;
         bin->fsize = avio_size(pb) - 1 - 192 - 4096;
         st->codecpar->width = 80<<3;
@@ -271,7 +271,7 @@ static int idf_read_header(AVFormatContext *s)
     AVStream *st;
     int got_width = 0;
 
-    if (!pb->seekable)
+    if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
         return AVERROR(EIO);
 
     st = init_stream(s);
diff --git a/libavformat/cafdec.c b/libavformat/cafdec.c
index 0e6179a56a..fc85fd9799 100644
--- a/libavformat/cafdec.c
+++ b/libavformat/cafdec.c
@@ -257,7 +257,7 @@ static int read_header(AVFormatContext *s)
 
         /* stop at data chunk if seeking is not supported or
            data chunk size is unknown */
-        if (found_data && (caf->data_size < 0 || !pb->seekable))
+        if (found_data && (caf->data_size < 0 || !(pb->seekable & AVIO_SEEKABLE_NORMAL)))
             break;
 
         tag  = avio_rb32(pb);
@@ -271,7 +271,7 @@ static int read_header(AVFormatContext *s)
             avio_skip(pb, 4); /* edit count */
             caf->data_start = avio_tell(pb);
             caf->data_size  = size < 0 ? -1 : size - 4;
-            if (caf->data_size > 0 && pb->seekable)
+            if (caf->data_size > 0 && (pb->seekable & AVIO_SEEKABLE_NORMAL))
                 avio_skip(pb, caf->data_size);
             found_data = 1;
             break;
diff --git a/libavformat/cafenc.c b/libavformat/cafenc.c
index 5ea8e69cc8..7aa9e8cee1 100644
--- a/libavformat/cafenc.c
+++ b/libavformat/cafenc.c
@@ -126,7 +126,7 @@ static int caf_write_header(AVFormatContext *s)
         return AVERROR_INVALIDDATA;
     }
 
-    if (!par->block_align && !pb->seekable) {
+    if (!par->block_align && !(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         av_log(s, AV_LOG_ERROR, "Muxing variable packet size not supported on non seekable output\n");
         return AVERROR_INVALIDDATA;
     }
@@ -236,7 +236,7 @@ static int caf_write_trailer(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     AVCodecParameters *par = s->streams[0]->codecpar;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t file_size = avio_tell(pb);
 
         avio_seek(pb, caf->data, SEEK_SET);
diff --git a/libavformat/cinedec.c b/libavformat/cinedec.c
index 32cccf566b..763b93ba2e 100644
--- a/libavformat/cinedec.c
+++ b/libavformat/cinedec.c
@@ -307,7 +307,7 @@ static int cine_read_seek(AVFormatContext *avctx, int stream_index, int64_t time
     if ((flags & AVSEEK_FLAG_FRAME) || (flags & AVSEEK_FLAG_BYTE))
         return AVERROR(ENOSYS);
 
-    if (!avctx->pb->seekable)
+    if (!(avctx->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return AVERROR(EIO);
 
     cine->pts = timestamp;
diff --git a/libavformat/dsfdec.c b/libavformat/dsfdec.c
index f16b397df2..49ca336427 100644
--- a/libavformat/dsfdec.c
+++ b/libavformat/dsfdec.c
@@ -77,7 +77,7 @@ static int dsf_read_header(AVFormatContext *s)
 
     avio_skip(pb, 8);
     id3pos = avio_rl64(pb);
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         read_id3(s, id3pos);
         avio_seek(pb, 28, SEEK_SET);
     }
diff --git a/libavformat/dtshddec.c b/libavformat/dtshddec.c
index f5f040773b..1bd403c843 100644
--- a/libavformat/dtshddec.c
+++ b/libavformat/dtshddec.c
@@ -89,7 +89,7 @@ static int dtshd_read_header(AVFormatContext *s)
             dtshd->data_end = data_start + chunk_size;
             if (dtshd->data_end <= chunk_size)
                 return AVERROR_INVALIDDATA;
-            if (!pb->seekable)
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
                 goto break_loop;
             goto skip;
             break;
diff --git a/libavformat/dv.c b/libavformat/dv.c
index 89a9e10c14..06de04485c 100644
--- a/libavformat/dv.c
+++ b/libavformat/dv.c
@@ -534,7 +534,7 @@ static int dv_read_header(AVFormatContext *s)
                                (AVRational) { 8, 1 },
                                c->dv_demux->sys->time_base);
 
-    if (s->pb->seekable)
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)
         dv_read_timecode(s);
 
     return 0;
diff --git a/libavformat/ffmdec.c b/libavformat/ffmdec.c
index f863bf7818..de6ac27252 100644
--- a/libavformat/ffmdec.c
+++ b/libavformat/ffmdec.c
@@ -300,7 +300,7 @@ static int ffm2_read_header(AVFormatContext *s)
 
     ffm->write_index = avio_rb64(pb);
     /* get also filesize */
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         ffm->file_size = avio_size(pb);
         if (ffm->write_index && 0)
             adjust_write_index(s);
@@ -559,7 +559,7 @@ static int ffm_read_header(AVFormatContext *s)
     }
     ffm->write_index = avio_rb64(pb);
     /* get also filesize */
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         ffm->file_size = avio_size(pb);
         if (ffm->write_index && 0)
             adjust_write_index(s);
diff --git a/libavformat/filmstripdec.c b/libavformat/filmstripdec.c
index 0aeb5947b0..0bf5a80830 100644
--- a/libavformat/filmstripdec.c
+++ b/libavformat/filmstripdec.c
@@ -41,7 +41,7 @@ static int read_header(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     AVStream *st;
 
-    if (!s->pb->seekable)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return AVERROR(EIO);
 
     avio_seek(pb, avio_size(pb) - 36, SEEK_SET);
diff --git a/libavformat/flacenc.c b/libavformat/flacenc.c
index 89b21e9e23..b894f9ef61 100644
--- a/libavformat/flacenc.c
+++ b/libavformat/flacenc.c
@@ -147,7 +147,7 @@ static int flac_write_trailer(struct AVFormatContext *s)
     if (!c->write_header || !streaminfo)
         return 0;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* rewrite the STREAMINFO header block data */
         file_size = avio_tell(pb);
         avio_seek(pb, 8, SEEK_SET);
diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index 3959a3665a..cdcfb9c5a0 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -484,7 +484,7 @@ static int amf_parse_object(AVFormatContext *s, AVStream *astream,
         break;
     case AMF_DATA_TYPE_OBJECT:
         if (key &&
-            ioc->seekable &&
+            (ioc->seekable & AVIO_SEEKABLE_NORMAL) &&
             !strcmp(KEYFRAMES_TAG, key) && depth == 1)
             if (parse_keyframes_index(s, ioc,
                                       max_pos) < 0)
@@ -1040,7 +1040,7 @@ skip:
         }
         av_log(s, AV_LOG_TRACE, "%d %X %d \n", stream_type, flags, st->discard);
 
-        if (s->pb->seekable &&
+        if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
             ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY ||
               stream_type == FLV_STREAM_TYPE_AUDIO))
             av_add_index_entry(st, pos, dts, size, 0, AVINDEX_KEYFRAME);
@@ -1056,7 +1056,8 @@ skip:
 
     // if not streamed and no duration from metadata then seek to end to find
     // the duration from the timestamps
-    if (s->pb->seekable && (!s->duration || s->duration == AV_NOPTS_VALUE) &&
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
+        (!s->duration || s->duration == AV_NOPTS_VALUE) &&
         !flv->searched_for_end) {
         int size;
         const int64_t pos   = avio_tell(s->pb);
diff --git a/libavformat/gxfenc.c b/libavformat/gxfenc.c
index 79951b59af..0e0772b744 100644
--- a/libavformat/gxfenc.c
+++ b/libavformat/gxfenc.c
@@ -709,7 +709,7 @@ static int gxf_write_header(AVFormatContext *s)
     int ret;
     AVDictionaryEntry *tcr = av_dict_get(s->metadata, "timecode", NULL, 0);
 
-    if (!pb->seekable) {
+    if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         av_log(s, AV_LOG_ERROR, "gxf muxer does not support streamed output, patch welcome\n");
         return -1;
     }
diff --git a/libavformat/icoenc.c b/libavformat/icoenc.c
index a7ada19fcd..e641f7bdc7 100644
--- a/libavformat/icoenc.c
+++ b/libavformat/icoenc.c
@@ -82,7 +82,7 @@ static int ico_write_header(AVFormatContext *s)
     int ret;
     int i;
 
-    if (!pb->seekable) {
+    if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         av_log(s, AV_LOG_ERROR, "Output is not seekable\n");
         return AVERROR(EINVAL);
     }
diff --git a/libavformat/id3v1.c b/libavformat/id3v1.c
index 218ed73f81..19be42121d 100644
--- a/libavformat/id3v1.c
+++ b/libavformat/id3v1.c
@@ -238,7 +238,7 @@ void ff_id3v1_read(AVFormatContext *s)
     uint8_t buf[ID3v1_TAG_SIZE];
     int64_t filesize, position = avio_tell(s->pb);
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* XXX: change that */
         filesize = avio_size(s->pb);
         if (filesize > 128) {
diff --git a/libavformat/ivfenc.c b/libavformat/ivfenc.c
index f3ae4dca66..fdc0ee03e1 100644
--- a/libavformat/ivfenc.c
+++ b/libavformat/ivfenc.c
@@ -75,7 +75,7 @@ static int ivf_write_trailer(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     IVFEncContext *ctx = s->priv_data;
 
-    if (pb->seekable && ctx->frame_cnt > 1) {
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && ctx->frame_cnt > 1) {
         size_t end = avio_tell(pb);
 
         avio_seek(pb, 24, SEEK_SET);
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index bad034b770..2e3c9bf197 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -1616,7 +1616,7 @@ static void matroska_execute_seekhead(MatroskaDemuxContext *matroska)
     int i;
 
     // we should not do any seeking in the streaming case
-    if (!matroska->ctx->pb->seekable)
+    if (!(matroska->ctx->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return;
 
     for (i = 0; i < seekhead_list->nb_elem; i++) {
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index df77313675..af941ceb8f 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -333,7 +333,7 @@ static int start_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, Matros
     if ((ret = avio_open_dyn_buf(dyn_cp)) < 0)
         return ret;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         *master = start_ebml_master(pb, elementid, expectedsize);
         if (mkv->write_crc && mkv->mode != MODE_WEBM)
             put_ebml_void(*dyn_cp, 6); /* Reserve space for CRC32 so position/size calculations using avio_tell() take it into account */
@@ -349,7 +349,7 @@ static void end_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, Matrosk
     uint8_t *buf, crc[4];
     int size, skip = 0;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         size = avio_close_dyn_buf(*dyn_cp, &buf);
         if (mkv->write_crc && mkv->mode != MODE_WEBM) {
             skip = 6; /* Skip reserved 6-byte long void element from the dynamic buffer. */
@@ -373,7 +373,7 @@ static void end_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, Matrosk
 static void end_ebml_master_crc32_preliminary(AVIOContext *pb, AVIOContext **dyn_cp, MatroskaMuxContext *mkv,
     ebml_master master)
 {
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
 
         uint8_t *buf;
         int size = avio_get_dyn_buf(*dyn_cp, &buf);
@@ -1419,7 +1419,7 @@ static int mkv_write_tracks(AVFormatContext *s)
             return ret;
     }
 
-    if (pb->seekable && !mkv->is_live)
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live)
         end_ebml_master_crc32_preliminary(pb, &mkv->tracks_bc, mkv, mkv->tracks_master);
     else
         end_ebml_master_crc32(pb, &mkv->tracks_bc, mkv, mkv->tracks_master);
@@ -1614,7 +1614,7 @@ static int mkv_write_tags(AVFormatContext *s)
         if (ret < 0) return ret;
     }
 
-    if (s->pb->seekable && !mkv->is_live) {
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live) {
         for (i = 0; i < s->nb_streams; i++) {
             AVIOContext *pb;
             AVStream *st = s->streams[i];
@@ -1664,7 +1664,7 @@ static int mkv_write_tags(AVFormatContext *s)
     }
 
     if (mkv->tags.pos) {
-        if (s->pb->seekable && !mkv->is_live)
+        if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live)
             end_ebml_master_crc32_preliminary(s->pb, &mkv->tags_bc, mkv, mkv->tags);
         else
             end_ebml_master_crc32(s->pb, &mkv->tags_bc, mkv, mkv->tags);
@@ -1921,7 +1921,7 @@ static int mkv_write_header(AVFormatContext *s)
             put_ebml_void(pb, 11);              // assumes double-precision float to be written
         }
     }
-    if (s->pb->seekable && !mkv->is_live)
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live)
         end_ebml_master_crc32_preliminary(s->pb, &mkv->info_bc, mkv, mkv->info);
     else
         end_ebml_master_crc32(s->pb, &mkv->info_bc, mkv, mkv->info);
@@ -1952,7 +1952,7 @@ static int mkv_write_header(AVFormatContext *s)
             goto fail;
     }
 
-    if (!s->pb->seekable && !mkv->is_live)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live)
         mkv_write_seekhead(pb, mkv);
 
     mkv->cues = mkv_start_cues(mkv->segment_offset);
@@ -1960,7 +1960,7 @@ static int mkv_write_header(AVFormatContext *s)
         ret = AVERROR(ENOMEM);
         goto fail;
     }
-    if (pb->seekable && mkv->reserve_cues_space) {
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && mkv->reserve_cues_space) {
         mkv->cues_pos = avio_tell(pb);
         put_ebml_void(pb, mkv->reserve_cues_space);
     }
@@ -1973,7 +1973,7 @@ static int mkv_write_header(AVFormatContext *s)
 
     // start a new cluster every 5 MB or 5 sec, or 32k / 1 sec for streaming or
     // after 4k and on a keyframe
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         if (mkv->cluster_time_limit < 0)
             mkv->cluster_time_limit = 5000;
         if (mkv->cluster_size_limit < 0)
@@ -2198,7 +2198,7 @@ static void mkv_start_new_cluster(AVFormatContext *s, AVPacket *pkt)
 
     end_ebml_master_crc32(s->pb, &mkv->dyn_bc, mkv, mkv->cluster);
     mkv->cluster_pos = -1;
-    if (s->pb->seekable)
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)
         av_log(s, AV_LOG_DEBUG,
                "Starting new cluster at offset %" PRIu64 " bytes, "
                "pts %" PRIu64 "dts %" PRIu64 "\n",
@@ -2223,7 +2223,7 @@ static int mkv_check_new_extra_data(AVFormatContext *s, AVPacket *pkt)
 
     switch (par->codec_id) {
     case AV_CODEC_ID_FLAC:
-        if (side_data_size && s->pb->seekable) {
+        if (side_data_size && (s->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
             AVCodecParameters *codecpriv_par;
             int64_t curpos;
             if (side_data_size != par->extradata_size) {
@@ -2296,7 +2296,7 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
 
     if (par->codec_type != AVMEDIA_TYPE_SUBTITLE) {
         mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe);
-        if (s->pb->seekable && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
+        if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
             ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
         }
@@ -2321,7 +2321,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
             end_ebml_master(pb, blockgroup);
         }
 
-        if (s->pb->seekable) {
+        if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
             ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts,
                                    mkv->cluster_pos, relative_packet_pos, duration);
             if (ret < 0)
@@ -2421,7 +2421,7 @@ static int mkv_write_flush_packet(AVFormatContext *s, AVPacket *pkt)
         if (mkv->cluster_pos != -1) {
             end_ebml_master_crc32(s->pb, &mkv->dyn_bc, mkv, mkv->cluster);
             mkv->cluster_pos = -1;
-            if (s->pb->seekable)
+            if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)
                 av_log(s, AV_LOG_DEBUG,
                        "Flushing cluster at offset %" PRIu64 " bytes\n",
                        avio_tell(s->pb));
@@ -2462,7 +2462,7 @@ static int mkv_write_trailer(AVFormatContext *s)
             return ret;
     }
 
-    if (pb->seekable && !mkv->is_live) {
+    if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live) {
         if (mkv->cues->num_entries) {
             if (mkv->reserve_cues_space) {
                 int64_t cues_end;
diff --git a/libavformat/mlvdec.c b/libavformat/mlvdec.c
index 665b28d4f8..90c3779e44 100644
--- a/libavformat/mlvdec.c
+++ b/libavformat/mlvdec.c
@@ -449,7 +449,7 @@ static int read_seek(AVFormatContext *avctx, int stream_index, int64_t timestamp
     if ((flags & AVSEEK_FLAG_FRAME) || (flags & AVSEEK_FLAG_BYTE))
         return AVERROR(ENOSYS);
 
-    if (!avctx->pb->seekable)
+    if (!(avctx->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return AVERROR(EIO);
 
     mlv->pts = timestamp;
diff --git a/libavformat/mmf.c b/libavformat/mmf.c
index b8a9cad32e..1393627d8a 100644
--- a/libavformat/mmf.c
+++ b/libavformat/mmf.c
@@ -147,7 +147,7 @@ static int mmf_write_trailer(AVFormatContext *s)
     int64_t pos, size;
     int gatetime;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* Fill in length fields */
         end_tag_be(pb, mmf->awapos);
         end_tag_be(pb, mmf->atrpos);
diff --git a/libavformat/mov.c b/libavformat/mov.c
index f7dd2502c5..3754346f9e 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -1166,7 +1166,7 @@ static int mov_read_moof(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
     if (!c->has_looked_for_mfra && c->use_mfra_for > 0) {
         c->has_looked_for_mfra = 1;
-        if (pb->seekable) {
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
             int ret;
             av_log(c->fc, AV_LOG_VERBOSE, "stream has moof boxes, will look "
                     "for a mfra\n");
@@ -5421,9 +5421,9 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
                 return err;
             }
             if (c->found_moov && c->found_mdat &&
-                ((!pb->seekable || c->fc->flags & AVFMT_FLAG_IGNIDX || c->fragment_index_complete) ||
+                ((!(pb->seekable & AVIO_SEEKABLE_NORMAL) || c->fc->flags & AVFMT_FLAG_IGNIDX || c->fragment_index_complete) ||
                  start_pos + a.size == avio_size(pb))) {
-                if (!pb->seekable || c->fc->flags & AVFMT_FLAG_IGNIDX || c->fragment_index_complete)
+                if (!(pb->seekable & AVIO_SEEKABLE_NORMAL) || c->fc->flags & AVFMT_FLAG_IGNIDX || c->fragment_index_complete)
                     c->next_root_atom = start_pos + a.size;
                 c->atom_depth --;
                 return 0;
@@ -5935,7 +5935,7 @@ static int mov_read_header(AVFormatContext *s)
     mov->fc = s;
     mov->trak_index = -1;
     /* .mov and .mp4 aren't streamable anyway (only progressive download if moov is before mdat) */
-    if (pb->seekable)
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL)
         atom.size = avio_size(pb);
     else
         atom.size = INT64_MAX;
@@ -5949,7 +5949,7 @@ static int mov_read_header(AVFormatContext *s)
         mov_read_close(s);
         return err;
     }
-    } while (pb->seekable && !mov->found_moov && !mov->moov_retry++);
+    } while ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !mov->found_moov && !mov->moov_retry++);
     if (!mov->found_moov) {
         av_log(s, AV_LOG_ERROR, "moov atom not found\n");
         mov_read_close(s);
@@ -5957,7 +5957,7 @@ static int mov_read_header(AVFormatContext *s)
     }
     av_log(mov->fc, AV_LOG_TRACE, "on_parse_exit_offset=%"PRId64"\n", avio_tell(pb));
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         if (mov->nb_chapter_tracks > 0 && !mov->ignore_chapters)
             mov_read_chapters(s);
         for (i = 0; i < s->nb_streams; i++)
@@ -6118,8 +6118,8 @@ static AVIndexEntry *mov_find_next_sample(AVFormatContext *s, AVStream **st)
             AVIndexEntry *current_sample = &avst->index_entries[msc->current_sample];
             int64_t dts = av_rescale(current_sample->timestamp, AV_TIME_BASE, msc->time_scale);
             av_log(s, AV_LOG_TRACE, "stream %d, sample %d, dts %"PRId64"\n", i, msc->current_sample, dts);
-            if (!sample || (!s->pb->seekable && current_sample->pos < sample->pos) ||
-                (s->pb->seekable &&
+            if (!sample || (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) && current_sample->pos < sample->pos) ||
+                ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
                  ((msc->pb != s->pb && dts < best_dts) || (msc->pb == s->pb &&
                  ((FFABS(best_dts - dts) <= AV_TIME_BASE && current_sample->pos < sample->pos) ||
                   (FFABS(best_dts - dts) > AV_TIME_BASE && dts < best_dts)))))) {
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index a28621080d..11b26708ae 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -5616,7 +5616,7 @@ static int mov_init(AVFormatContext *s)
 
     /* Non-seekable output is ok if using fragmentation. If ism_lookahead
      * is enabled, we don't support non-seekable output at all. */
-    if (!s->pb->seekable &&
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
         (!(mov->flags & FF_MOV_FLAG_FRAGMENT) || mov->ism_lookahead)) {
         av_log(s, AV_LOG_ERROR, "muxer does not support non seekable output\n");
         return AVERROR(EINVAL);
diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index b45a066686..0924a57843 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -370,7 +370,7 @@ static int mp3_read_header(AVFormatContext *s)
     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
         ff_id3v1_read(s);
 
-    if(s->pb->seekable)
+    if(s->pb->seekable & AVIO_SEEKABLE_NORMAL)
         mp3->filesize = avio_size(s->pb);
 
     if (mp3_parse_vbr_tags(s, st, off) < 0)
diff --git a/libavformat/mp3enc.c b/libavformat/mp3enc.c
index 49f3742dc4..034862261a 100644
--- a/libavformat/mp3enc.c
+++ b/libavformat/mp3enc.c
@@ -144,7 +144,7 @@ static int mp3_write_xing(AVFormatContext *s)
     int ver = 0;
     int bytes_needed;
 
-    if (!s->pb->seekable || !mp3->write_xing)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) || !mp3->write_xing)
         return 0;
 
     for (i = 0; i < FF_ARRAY_ELEMS(avpriv_mpa_freq_tab); i++) {
diff --git a/libavformat/mpc.c b/libavformat/mpc.c
index 4bd1f5018b..af333746e3 100644
--- a/libavformat/mpc.c
+++ b/libavformat/mpc.c
@@ -104,7 +104,7 @@ static int mpc_read_header(AVFormatContext *s)
     st->duration = c->fcount;
 
     /* try to read APE tags */
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t pos = avio_tell(s->pb);
         ff_ape_parse_tag(s);
         if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
diff --git a/libavformat/mpc8.c b/libavformat/mpc8.c
index 05d0c1ae86..180c554c00 100644
--- a/libavformat/mpc8.c
+++ b/libavformat/mpc8.c
@@ -264,7 +264,7 @@ static int mpc8_read_header(AVFormatContext *s)
     if (size > 0)
         avio_skip(pb, size);
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t pos = avio_tell(s->pb);
         c->apetag_start = ff_ape_parse_tag(s);
         avio_seek(s->pb, pos, SEEK_SET);
diff --git a/libavformat/mpeg.c b/libavformat/mpeg.c
index a651cb3eb6..68a848a6f6 100644
--- a/libavformat/mpeg.c
+++ b/libavformat/mpeg.c
@@ -451,7 +451,7 @@ redo:
         int i;
         for (i = 0; i < s->nb_streams; i++) {
             if (startcode == s->streams[i]->id &&
-                s->pb->seekable /* index useless on streams anyway */) {
+                (s->pb->seekable & AVIO_SEEKABLE_NORMAL) /* index useless on streams anyway */) {
                 ff_reduce_index(s, i);
                 av_add_index_entry(s->streams[i], *ppos, dts, 0, 0,
                                    AVINDEX_KEYFRAME /* FIXME keyframe? */);
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 590abb04f1..3eff1522bd 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2605,7 +2605,7 @@ static void seek_back(AVFormatContext *s, AVIOContext *pb, int64_t pos) {
      * probe buffer usually is big enough. Only warn if the seek failed
      * on files where the seek should work. */
     if (avio_seek(pb, pos, SEEK_SET) < 0)
-        av_log(s, pb->seekable ? AV_LOG_ERROR : AV_LOG_INFO, "Unable to seek back to the start\n");
+        av_log(s, (pb->seekable & AVIO_SEEKABLE_NORMAL) ? AV_LOG_ERROR : AV_LOG_INFO, "Unable to seek back to the start\n");
 }
 
 static int mpegts_read_header(AVFormatContext *s)
diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
index f0a29ebe57..0e12c8c6c1 100644
--- a/libavformat/mvdec.c
+++ b/libavformat/mvdec.c
@@ -421,7 +421,7 @@ static int mv_read_packet(AVFormatContext *avctx, AVPacket *pkt)
         if (index->pos > pos)
             avio_skip(pb, index->pos - pos);
         else if (index->pos < pos) {
-            if (!pb->seekable)
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
                 return AVERROR(EIO);
             ret = avio_seek(pb, index->pos, SEEK_SET);
             if (ret < 0)
@@ -463,7 +463,7 @@ static int mv_read_seek(AVFormatContext *avctx, int stream_index,
     if ((flags & AVSEEK_FLAG_FRAME) || (flags & AVSEEK_FLAG_BYTE))
         return AVERROR(ENOSYS);
 
-    if (!avctx->pb->seekable)
+    if (!(avctx->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return AVERROR(EIO);
 
     frame = av_index_search_timestamp(st, timestamp, flags);
diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 2ad0c288f8..f8d0f9e057 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -2590,7 +2590,7 @@ static int mxf_parse_handle_essence(MXFContext *mxf)
         /* remember where we were so we don't end up seeking further back than this */
         mxf->last_forward_tell = avio_tell(pb);
 
-        if (!pb->seekable) {
+        if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
             av_log(mxf->fc, AV_LOG_INFO, "file is not seekable - not parsing FooterPartition\n");
             return -1;
         }
@@ -2777,7 +2777,7 @@ static void mxf_read_random_index_pack(AVFormatContext *s)
     int64_t file_size, max_rip_length, min_rip_length;
     KLVPacket klv;
 
-    if (!s->pb->seekable)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return;
 
     file_size = avio_size(s->pb);
diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
index afea117d5a..12fc9abbc6 100644
--- a/libavformat/mxfenc.c
+++ b/libavformat/mxfenc.c
@@ -2549,7 +2549,7 @@ static int mxf_write_footer(AVFormatContext *s)
     mxf_write_klv_fill(s);
     mxf_write_random_index_pack(s);
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         if (s->oformat == &ff_mxf_opatom_muxer){
             /* rewrite body partition to update lengths */
             avio_seek(pb, mxf->body_partition_offset[0], SEEK_SET);
diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
index 2e309bcad7..ca34e35f74 100644
--- a/libavformat/nutdec.c
+++ b/libavformat/nutdec.c
@@ -876,7 +876,7 @@ static int nut_read_header(AVFormatContext *s)
 
     s->internal->data_offset = pos - 8;
 
-    if (bc->seekable) {
+    if (bc->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t orig_pos = avio_tell(bc);
         find_and_decode_index(nut);
         avio_seek(bc, orig_pos, SEEK_SET);
diff --git a/libavformat/oggdec.c b/libavformat/oggdec.c
index edeae2ba83..97ad1a27d1 100644
--- a/libavformat/oggdec.c
+++ b/libavformat/oggdec.c
@@ -209,7 +209,7 @@ static int ogg_replace_stream(AVFormatContext *s, uint32_t serial, int nsegs)
     const struct ogg_codec *codec;
     int i = 0;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         uint8_t magic[8];
         int64_t pos = avio_tell(s->pb);
         avio_skip(s->pb, nsegs);
@@ -355,7 +355,7 @@ static int ogg_read_page(AVFormatContext *s, int *sid)
             sync[(sp + 2) & 3] == 'g' && sync[(sp + 3) & 3] == 'S')
             break;
 
-        if(!i && bc->seekable && ogg->page_pos > 0) {
+        if(!i && (bc->seekable & AVIO_SEEKABLE_NORMAL) && ogg->page_pos > 0) {
             memset(sync, 0, 4);
             avio_seek(bc, ogg->page_pos+4, SEEK_SET);
             ogg->page_pos = -1;
@@ -613,7 +613,7 @@ static int ogg_get_length(AVFormatContext *s)
     int64_t size, end;
     int streams_left=0;
 
-    if (!s->pb->seekable)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return 0;
 
 // already set
diff --git a/libavformat/r3d.c b/libavformat/r3d.c
index b609488839..1f53d847e9 100644
--- a/libavformat/r3d.c
+++ b/libavformat/r3d.c
@@ -186,7 +186,7 @@ static int r3d_read_header(AVFormatContext *s)
 
     s->internal->data_offset = avio_tell(s->pb);
     av_log(s, AV_LOG_TRACE, "data offset %#"PRIx64"\n", s->internal->data_offset);
-    if (!s->pb->seekable)
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
         return 0;
     // find REOB/REOF/REOS to load index
     avio_seek(s->pb, avio_size(s->pb)-48-8, SEEK_SET);
diff --git a/libavformat/rawenc.c b/libavformat/rawenc.c
index 0edcd1cf99..26baa850e1 100644
--- a/libavformat/rawenc.c
+++ b/libavformat/rawenc.c
@@ -65,7 +65,7 @@ static int adx_write_trailer(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     AVCodecParameters *par = s->streams[0]->codecpar;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t file_size = avio_tell(pb);
         uint64_t sample_count = (file_size - 36) / par->channels / 18 * 32;
         if (sample_count <= UINT32_MAX) {
diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index 222c43378c..e6a1fe8842 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -651,7 +651,8 @@ static int rm_read_header(AVFormatContext *s)
 
     if (!data_off)
         data_off = avio_tell(pb) - 18;
-    if (indx_off && pb->seekable && !(s->flags & AVFMT_FLAG_IGNIDX) &&
+    if (indx_off && (pb->seekable & AVIO_SEEKABLE_NORMAL) &&
+        !(s->flags & AVFMT_FLAG_IGNIDX) &&
         avio_seek(pb, indx_off, SEEK_SET) >= 0) {
         rm_read_index(s);
         avio_seek(pb, data_off + 18, SEEK_SET);
diff --git a/libavformat/rmenc.c b/libavformat/rmenc.c
index 0bc5bfd92b..f9821d1875 100644
--- a/libavformat/rmenc.c
+++ b/libavformat/rmenc.c
@@ -123,7 +123,7 @@ static int rv10_write_header(AVFormatContext *ctx,
     avio_wb32(s, 0);           /* data offset : will be patched after */
     avio_wb16(s, ctx->nb_streams);    /* num streams */
     flags = 1 | 2; /* save allowed & perfect play */
-    if (!s->seekable)
+    if (!(s->seekable & AVIO_SEEKABLE_NORMAL))
         flags |= 4; /* live broadcast */
     avio_wb16(s, flags);
 
@@ -175,7 +175,7 @@ static int rv10_write_header(AVFormatContext *ctx,
         avio_wb32(s, 0);           /* start time */
         avio_wb32(s, BUFFER_DURATION);           /* preroll */
         /* duration */
-        if (!s->seekable || !stream->total_frames)
+        if (!(s->seekable & AVIO_SEEKABLE_NORMAL) || !stream->total_frames)
             avio_wb32(s, (int)(3600 * 1000));
         else
             avio_wb32(s, av_rescale_q_rnd(stream->total_frames, (AVRational){1000, 1},  stream->frame_rate, AV_ROUND_ZERO));
@@ -444,7 +444,7 @@ static int rm_write_trailer(AVFormatContext *s)
     int data_size, index_pos, i;
     AVIOContext *pb = s->pb;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* end of file: finish to write header */
         index_pos = avio_tell(pb);
         data_size = index_pos - rm->data_pos;
diff --git a/libavformat/rsd.c b/libavformat/rsd.c
index 5a56e72bb3..27a3d73981 100644
--- a/libavformat/rsd.c
+++ b/libavformat/rsd.c
@@ -106,12 +106,12 @@ static int rsd_read_header(AVFormatContext *s)
         break;
     case AV_CODEC_ID_ADPCM_PSX:
         par->block_align = 16 * par->channels;
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = av_get_audio_frame_duration2(par, avio_size(pb) - start);
         break;
     case AV_CODEC_ID_ADPCM_IMA_RAD:
         par->block_align = 20 * par->channels;
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = av_get_audio_frame_duration2(par, avio_size(pb) - start);
         break;
     case AV_CODEC_ID_ADPCM_IMA_WAV:
@@ -120,7 +120,7 @@ static int rsd_read_header(AVFormatContext *s)
 
         par->bits_per_coded_sample = 4;
         par->block_align = 36 * par->channels;
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = av_get_audio_frame_duration2(par, avio_size(pb) - start);
         break;
     case AV_CODEC_ID_ADPCM_THP_LE:
@@ -131,7 +131,7 @@ static int rsd_read_header(AVFormatContext *s)
 
         if ((ret = ff_get_extradata(s, par, s->pb, 32)) < 0)
             return ret;
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = av_get_audio_frame_duration2(par, avio_size(pb) - start);
         break;
     case AV_CODEC_ID_ADPCM_THP:
@@ -145,7 +145,7 @@ static int rsd_read_header(AVFormatContext *s)
             avio_read(s->pb, st->codecpar->extradata + 32 * i, 32);
             avio_skip(s->pb, 8);
         }
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = (avio_size(pb) - start) / (8 * par->channels) * 14;
         break;
     case AV_CODEC_ID_PCM_S16LE:
@@ -153,7 +153,7 @@ static int rsd_read_header(AVFormatContext *s)
         if (version != 4)
             start = avio_rl32(pb);
 
-        if (pb->seekable)
+        if (pb->seekable & AVIO_SEEKABLE_NORMAL)
             st->duration = (avio_size(pb) - start) / 2 / par->channels;
         break;
     }
diff --git a/libavformat/rsoenc.c b/libavformat/rsoenc.c
index 3c5c1180f5..60ebac8ebd 100644
--- a/libavformat/rsoenc.c
+++ b/libavformat/rsoenc.c
@@ -38,7 +38,7 @@ static int rso_write_header(AVFormatContext *s)
         return AVERROR_INVALIDDATA;
     }
 
-    if (!s->pb->seekable) {
+    if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         av_log(s, AV_LOG_ERROR, "muxer does not support non seekable output\n");
         return AVERROR_INVALIDDATA;
     }
diff --git a/libavformat/smjpegenc.c b/libavformat/smjpegenc.c
index 314593a5c9..68a128647e 100644
--- a/libavformat/smjpegenc.c
+++ b/libavformat/smjpegenc.c
@@ -121,7 +121,7 @@ static int smjpeg_write_trailer(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     int64_t currentpos;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         currentpos = avio_tell(pb);
         avio_seek(pb, 12, SEEK_SET);
         avio_wb32(pb, smc->duration);
diff --git a/libavformat/soxenc.c b/libavformat/soxenc.c
index b307157856..7b37bd4848 100644
--- a/libavformat/soxenc.c
+++ b/libavformat/soxenc.c
@@ -91,7 +91,7 @@ static int sox_write_trailer(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     AVCodecParameters *par = s->streams[0]->codecpar;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         /* update number of samples */
         int64_t file_size = avio_tell(pb);
         int64_t num_samples = (file_size - sox->header_size - 4LL) >> 2LL;
diff --git a/libavformat/swfenc.c b/libavformat/swfenc.c
index 3733a0442c..cada45ef9a 100644
--- a/libavformat/swfenc.c
+++ b/libavformat/swfenc.c
@@ -500,7 +500,7 @@ static int swf_write_trailer(AVFormatContext *s)
     put_swf_end_tag(s);
 
     /* patch file size and number of frames if not streamed */
-    if (s->pb->seekable && video_par) {
+    if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && video_par) {
         file_size = avio_tell(pb);
         avio_seek(pb, 4, SEEK_SET);
         avio_wl32(pb, file_size);
diff --git a/libavformat/takdec.c b/libavformat/takdec.c
index a8fb363b34..1535bec64f 100644
--- a/libavformat/takdec.c
+++ b/libavformat/takdec.c
@@ -128,7 +128,7 @@ static int tak_read_header(AVFormatContext *s)
         case TAK_METADATA_END: {
             int64_t curpos = avio_tell(pb);
 
-            if (pb->seekable) {
+            if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
                 ff_ape_parse_tag(s);
                 avio_seek(pb, curpos, SEEK_SET);
             }
diff --git a/libavformat/tta.c b/libavformat/tta.c
index 1447effcd8..ae90a85544 100644
--- a/libavformat/tta.c
+++ b/libavformat/tta.c
@@ -136,7 +136,7 @@ static int tta_read_header(AVFormatContext *s)
     st->codecpar->sample_rate = samplerate;
     st->codecpar->bits_per_coded_sample = bps;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t pos = avio_tell(s->pb);
         ff_ape_parse_tag(s);
         avio_seek(s->pb, pos, SEEK_SET);
diff --git a/libavformat/tty.c b/libavformat/tty.c
index b407645ee4..8d48f2c45c 100644
--- a/libavformat/tty.c
+++ b/libavformat/tty.c
@@ -94,7 +94,7 @@ static int read_header(AVFormatContext *avctx)
     /* simulate tty display speed */
     s->chars_per_frame = FFMAX(av_q2d(st->time_base)*s->chars_per_frame, 1);
 
-    if (avctx->pb->seekable) {
+    if (avctx->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         s->fsize = avio_size(avctx->pb);
         st->duration = (s->fsize + s->chars_per_frame - 1) / s->chars_per_frame;
 
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 8227d1bbe1..a059046a2c 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2857,7 +2857,7 @@ static void estimate_timings(AVFormatContext *ic, int64_t old_offset)
 
     if ((!strcmp(ic->iformat->name, "mpeg") ||
          !strcmp(ic->iformat->name, "mpegts")) &&
-        file_size && ic->pb->seekable) {
+        file_size && (ic->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         /* get accurate estimate from the PTSes */
         estimate_timings_from_pts(ic, old_offset);
         ic->duration_estimation_method = AVFMT_DURATION_FROM_PTS;
diff --git a/libavformat/vc1testenc.c b/libavformat/vc1testenc.c
index 60fb894a97..cf95d1d80d 100644
--- a/libavformat/vc1testenc.c
+++ b/libavformat/vc1testenc.c
@@ -73,7 +73,7 @@ static int vc1test_write_trailer(AVFormatContext *s)
     RCVContext *ctx = s->priv_data;
     AVIOContext *pb = s->pb;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         avio_seek(pb, 0, SEEK_SET);
         avio_wl24(pb, ctx->frames);
         avio_flush(pb);
diff --git a/libavformat/voc_packet.c b/libavformat/voc_packet.c
index 4f60467ac4..1e2e19e1c3 100644
--- a/libavformat/voc_packet.c
+++ b/libavformat/voc_packet.c
@@ -49,7 +49,7 @@ ff_voc_get_packet(AVFormatContext *s, AVPacket *pkt, AVStream *st, int max_size)
             return AVERROR_EOF;
         voc->remaining_size = avio_rl24(pb);
         if (!voc->remaining_size) {
-            if (!s->pb->seekable)
+            if (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL))
                 return AVERROR(EIO);
             voc->remaining_size = avio_size(pb) - avio_tell(pb);
         }
diff --git a/libavformat/wavdec.c b/libavformat/wavdec.c
index 0ca1ef42f8..a3cd4ffa06 100644
--- a/libavformat/wavdec.c
+++ b/libavformat/wavdec.c
@@ -410,7 +410,7 @@ static int wav_read_header(AVFormatContext *s)
             got_xma2 = 1;
             break;
         case MKTAG('d', 'a', 't', 'a'):
-            if (!pb->seekable && !got_fmt && !got_xma2) {
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL) && !got_fmt && !got_xma2) {
                 av_log(s, AV_LOG_ERROR,
                        "found no 'fmt ' tag before the 'data' tag\n");
                 return AVERROR_INVALIDDATA;
@@ -433,7 +433,7 @@ static int wav_read_header(AVFormatContext *s)
             /* don't look for footer metadata if we can't seek or if we don't
              * know where the data tag ends
              */
-            if (!pb->seekable || (!rf64 && !size))
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL) || (!rf64 && !size))
                 goto break_loop;
             break;
         case MKTAG('f', 'a', 'c', 't'):
@@ -821,7 +821,7 @@ static int w64_read_header(AVFormatContext *s)
             wav->data_end = avio_tell(pb) + size - 24;
 
             data_ofs = avio_tell(pb);
-            if (!pb->seekable)
+            if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
                 break;
 
             avio_skip(pb, size - 24);
diff --git a/libavformat/wavenc.c b/libavformat/wavenc.c
index a21d4c547e..7f3059e99a 100644
--- a/libavformat/wavenc.c
+++ b/libavformat/wavenc.c
@@ -344,7 +344,7 @@ static int wav_write_header(AVFormatContext *s)
     }
 
     if (s->streams[0]->codecpar->codec_tag != 0x01 /* hence for all other than PCM */
-        && s->pb->seekable) {
+        && (s->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         wav->fact_pos = ff_start_tag(pb, "fact");
         avio_wl32(pb, 0);
         ff_end_tag(pb, wav->fact_pos);
@@ -425,7 +425,7 @@ static int wav_write_trailer(AVFormatContext *s)
 
     avio_flush(pb);
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         if (wav->write_peak != 2 && avio_tell(pb) - wav->data < UINT32_MAX) {
             ff_end_tag(pb, wav->data);
             avio_flush(pb);
@@ -584,7 +584,7 @@ static int w64_write_header(AVFormatContext *s)
     end_guid(pb, start);
 
     if (s->streams[0]->codecpar->codec_tag != 0x01 /* hence for all other than PCM */
-        && s->pb->seekable) {
+        && (s->pb->seekable & AVIO_SEEKABLE_NORMAL)) {
         start_guid(pb, ff_w64_guid_fact, &wav->fact_pos);
         avio_wl64(pb, 0);
         end_guid(pb, wav->fact_pos);
@@ -601,7 +601,7 @@ static int w64_write_trailer(AVFormatContext *s)
     WAVMuxContext *wav = s->priv_data;
     int64_t file_size;
 
-    if (pb->seekable) {
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
         end_guid(pb, wav->data);
 
         file_size = avio_tell(pb);
diff --git a/libavformat/wvdec.c b/libavformat/wvdec.c
index 1ec52f689d..261fcaf35e 100644
--- a/libavformat/wvdec.c
+++ b/libavformat/wvdec.c
@@ -119,7 +119,7 @@ static int wv_read_block_header(AVFormatContext *ctx, AVIOContext *pb)
     }
     if ((rate == -1 || !chan) && !wc->block_parsed) {
         int64_t block_end = avio_tell(pb) + wc->header.blocksize;
-        if (!pb->seekable) {
+        if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
             av_log(ctx, AV_LOG_ERROR,
                    "Cannot determine additional parameters\n");
             return AVERROR_INVALIDDATA;
@@ -241,7 +241,7 @@ static int wv_read_header(AVFormatContext *s)
     if (wc->header.total_samples != 0xFFFFFFFFu)
         st->duration = wc->header.total_samples;
 
-    if (s->pb->seekable) {
+    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
         int64_t cur = avio_tell(s->pb);
         wc->apetag_start = ff_ape_parse_tag(s);
         if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
diff --git a/libavformat/wvenc.c b/libavformat/wvenc.c
index 48e371aa13..8743739e8d 100644
--- a/libavformat/wvenc.c
+++ b/libavformat/wvenc.c
@@ -64,7 +64,7 @@ static av_cold int wv_write_trailer(AVFormatContext *ctx)
     WvMuxContext *s = ctx->priv_data;
 
     /* update total number of samples in the first block */
-    if (ctx->pb->seekable && s->samples &&
+    if ((ctx->pb->seekable & AVIO_SEEKABLE_NORMAL) && s->samples &&
         s->samples < UINT32_MAX) {
         int64_t pos = avio_tell(ctx->pb);
         avio_seek(ctx->pb, 12, SEEK_SET);