mov: Support default-base-is-moof.

default-base-is-moof shall be set to track fragments compatible with DASH
Media Segments. So, this is a fundamental support for ISOBMFF ver. DASH.
This is meaningful only when base-data-offset-present is absent and two or
more track fragments are present in a movie fragment.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/isom.h

@@ -73,6 +73,7 @@ typedef struct MOVFragment {
     unsigned track_id;
     uint64_t base_data_offset;
     uint64_t moof_offset;
+    uint64_t implicit_offset;
     unsigned stsd_id;
     unsigned duration;
     unsigned size;
@@ -174,6 +175,7 @@ void ff_mp4_parse_es_descr(AVIOContext *pb, int *es_id);
 #define MOV_TFHD_DEFAULT_SIZE           0x10
 #define MOV_TFHD_DEFAULT_FLAGS          0x20
 #define MOV_TFHD_DURATION_IS_EMPTY  0x010000
+#define MOV_TFHD_DEFAULT_BASE_IS_MOOF 0x020000
 
 #define MOV_TRUN_DATA_OFFSET            0x01
 #define MOV_TRUN_FIRST_SAMPLE_FLAGS     0x04

libavformat/mov.c

@@ -725,7 +725,7 @@ static int mov_read_moov(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
 static int mov_read_moof(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
-    c->fragment.moof_offset = avio_tell(pb) - 8;
+    c->fragment.moof_offset = c->fragment.implicit_offset = avio_tell(pb) - 8;
     av_dlog(c->fc, "moof offset %"PRIx64"\n", c->fragment.moof_offset);
     return mov_read_default(c, pb, atom);
 }
@@ -2502,7 +2502,8 @@ static int mov_read_tfhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     }
 
     frag->base_data_offset = flags & MOV_TFHD_BASE_DATA_OFFSET ?
-                             avio_rb64(pb) : frag->moof_offset;
+                             avio_rb64(pb) : flags & MOV_TFHD_DEFAULT_BASE_IS_MOOF ?
+                             frag->moof_offset : frag->implicit_offset;
     frag->stsd_id  = flags & MOV_TFHD_STSD_ID ? avio_rb32(pb) : trex->stsd_id;
 
     frag->duration = flags & MOV_TFHD_DEFAULT_DURATION ?
@@ -2638,7 +2639,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     if (pb->eof_reached)
         return AVERROR_EOF;
 
-    frag->moof_offset = offset;
+    frag->implicit_offset = offset;
     st->duration = sc->track_end = dts + sc->time_offset;
     return 0;
 }