h264_mp4toannexb: Simplify extradata insertion

Up until now, h264_mp4toannexb stored the offset of the first SPS and
the first PPS in the (output) extradata in its context and used these
two numbers together with the size of the extradata and the pointer to
the extradata to determine what to insert when inserting extradata. This
led to some very long lines like "s->pps_offset != -1 ? s->pps_offset :
ctx->par_out->extradata_size - s->sps_offset". Therefore now pointers to
SPS and PPS are stored along with their respective sizes, so that e.g.
the above line can be changed to "s->sps_size".

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/h264_mp4toannexb_bsf.c

@@ -31,8 +31,10 @@
 #include "h264.h"
 
 typedef struct H264BSFContext {
-    int32_t  sps_offset;
-    int32_t  pps_offset;
+    uint8_t *sps;
+    uint8_t *pps;
+    int      sps_size;
+    int      pps_size;
     uint8_t  length_size;
     uint8_t  new_idr;
     uint8_t  idr_sps_seen;
@@ -72,12 +74,9 @@ static int h264_extradata_to_annexb(AVBSFContext *ctx, const int padding)
     GetByteContext ogb, *gb = &ogb;
     uint16_t unit_size;
     uint32_t total_size                 = 0;
-    uint8_t *out                        = NULL, unit_nb, sps_done = 0,
-             sps_seen                   = 0, pps_seen = 0;
+    uint8_t *out                        = NULL, unit_nb, sps_done = 0;
     static const uint8_t nalu_header[4] = { 0, 0, 0, 1 };
-    int length_size;
-
-    s->sps_offset = s->pps_offset = -1;
+    int length_size, pps_offset = 0;
 
     bytestream2_init(gb, ctx->par_in->extradata, ctx->par_in->extradata_size);
 
@@ -90,9 +89,6 @@ static int h264_extradata_to_annexb(AVBSFContext *ctx, const int padding)
     unit_nb = bytestream2_get_byteu(gb) & 0x1f; /* number of sps unit(s) */
     if (!unit_nb) {
         goto pps;
-    } else {
-        s->sps_offset = 0;
-        sps_seen = 1;
     }
 
     while (unit_nb--) {
@@ -115,25 +111,29 @@ static int h264_extradata_to_annexb(AVBSFContext *ctx, const int padding)
 pps:
         if (!unit_nb && !sps_done++) {
             unit_nb = bytestream2_get_byteu(gb); /* number of pps unit(s) */
-            if (unit_nb) {
-                s->pps_offset = total_size;
-                pps_seen = 1;
-            }
+            pps_offset = total_size;
         }
     }
 
     if (out)
         memset(out + total_size, 0, padding);
 
-    if (!sps_seen)
+    if (pps_offset) {
+        s->sps      = out;
+        s->sps_size = pps_offset;
+    } else {
         av_log(ctx, AV_LOG_WARNING,
                "Warning: SPS NALU missing or invalid. "
                "The resulting stream may not play.\n");
-
-    if (!pps_seen)
+    }
+    if (pps_offset < total_size) {
+        s->pps      = out + pps_offset;
+        s->pps_size = total_size - pps_offset;
+    } else {
         av_log(ctx, AV_LOG_WARNING,
                "Warning: PPS NALU missing or invalid. "
                "The resulting stream may not play.\n");
+    }
 
     av_freep(&ctx->par_out->extradata);
     ctx->par_out->extradata      = out;
@@ -220,12 +220,12 @@ static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *out)
             s->idr_pps_seen = s->new_idr = 1;
             /* if SPS has not been seen yet, prepend the AVCC one to PPS */
             if (!s->idr_sps_seen) {
-                if (s->sps_offset == -1)
+                if (!s->sps_size)
                     av_log(ctx, AV_LOG_WARNING, "SPS not present in the stream, nor in AVCC, stream may be unreadable\n");
                 else {
                     if ((ret = alloc_and_copy(out,
-                                         ctx->par_out->extradata + s->sps_offset,
-                                         s->pps_offset != -1 ? s->pps_offset : ctx->par_out->extradata_size - s->sps_offset,
+                                         s->sps,
+                                         s->sps_size,
                                          buf, nal_size, 1)) < 0)
                         goto fail;
                     s->idr_sps_seen = 1;
@@ -249,12 +249,12 @@ static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *out)
             s->new_idr = 0;
         /* if only SPS has been seen, also insert PPS */
         } else if (s->new_idr && unit_type == H264_NAL_IDR_SLICE && s->idr_sps_seen && !s->idr_pps_seen) {
-            if (s->pps_offset == -1) {
+            if (!s->pps_size) {
                 av_log(ctx, AV_LOG_WARNING, "PPS not present in the stream, nor in AVCC, stream may be unreadable\n");
                 if ((ret = alloc_and_copy(out, NULL, 0, buf, nal_size, 0)) < 0)
                     goto fail;
             } else if ((ret = alloc_and_copy(out,
-                                        ctx->par_out->extradata + s->pps_offset, ctx->par_out->extradata_size - s->pps_offset,
+                                        s->pps, s->pps_size,
                                         buf, nal_size, 1)) < 0)
                 goto fail;
         } else {