[FFmpeg-devel] [PATCH] avformat/mov: parse the last moof box when mp4 segment format

[1035567130@qq.com]

From: Wang Yaqiang <wangyaqiang03@kuaishou.com>

In the format of mp4 segment, the bitrate calculation of
stream depends on the sample_size in moof->traf->trun box.
In the original logic, when the last sidx box is read,
it is not parsed backwards, and the total sample_size calculation is smaller.
As a result, the bitrate displayed by ffprobe is also smaller than the actual.
Increasing the moof_count variable ensures that the last moof is parsed.

Test method: You can use -c copy remux a fmp4 file as mp4
and ffprobe the two files will find that the bitrate is inconsistent
Befor patch:
Stream #0:1[0x2](und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 59 kb/s
After patch:
Stream #0:1[0x2](und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96 kb/s (default)

Signed-off-by: Wang Yaqiang <wangyaqiang03@kuaishou.com>
---
 libavformat/isom.h | 1 +
 libavformat/mov.c  | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/libavformat/isom.h b/libavformat/isom.h
index f05c2d9c28..183a3c486b 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -296,6 +296,7 @@ typedef struct MOVContext {
     int has_looked_for_mfra;
     int use_tfdt;
     MOVFragmentIndex frag_index;
+    int moof_count; //ensure last fragment parse moof box
     int atom_depth;
     unsigned int aax_mode;  ///< 'aax' file has been detected
     uint8_t file_key[20];
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 14550e6456..396658e342 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -7784,12 +7784,15 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             int64_t start_pos = avio_tell(pb);
             int64_t left;
             int err = parse(c, pb, a);
+            if (a.type == MKTAG('m','o','o','f')) {
+                c->moof_count ++;
+            }
             if (err < 0) {
                 c->atom_depth --;
                 return err;
             }
             if (c->found_moov && c->found_mdat && a.size <= INT64_MAX - start_pos &&
-                ((!(pb->seekable & AVIO_SEEKABLE_NORMAL) || c->fc->flags & AVFMT_FLAG_IGNIDX || c->frag_index.complete) ||
+                ((!(pb->seekable & AVIO_SEEKABLE_NORMAL) || c->fc->flags & AVFMT_FLAG_IGNIDX || (c->frag_index.complete && c->moof_count >= c->frag_index.nb_items)) ||
                  start_pos + a.size == avio_size(pb))) {
                 if (!(pb->seekable & AVIO_SEEKABLE_NORMAL) || c->fc->flags & AVFMT_FLAG_IGNIDX || c->frag_index.complete)
                     c->next_root_atom = start_pos + a.size;
@@ -8361,6 +8364,9 @@ static int mov_read_header(AVFormatContext *s)
         av_log(s, AV_LOG_ERROR, "moov atom not found\n");
         return AVERROR_INVALIDDATA;
     }
+    if (mov->frag_index.nb_items > mov->moof_count) {
+        av_log(s, AV_LOG_WARNING, "the number of moof is less then fragment count\n");
+    }
     av_log(mov->fc, AV_LOG_TRACE, "on_parse_exit_offset=%"PRId64"\n", avio_tell(pb));
 
     if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
-- 
2.33.0

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