ping
> 2022年9月1日 18:22，1035567...@qq.com 写道：
>
> From: Wang Yaqiang <wangyaqian...@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 <wangyaqian...@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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