[FFmpeg-devel] [PATCH 2/2] mov: fix non-monotonous DTS when fragments overlap in time

[Michael Niedermayer]

On Fri, Sep 29, 2017 at 08:54:09AM -0700, John Stebbins wrote:
> ---
>  libavformat/mov.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index c7422cd9ed..871f10b240 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -4267,6 +4267,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>      int data_offset = 0;
>      unsigned entries, first_sample_flags = frag->flags;
>      int flags, distance, i;
> +    AVIndexEntry *last_index_entry = NULL;
>  
>      for (i = 0; i < c->fc->nb_streams; i++) {
>          if (c->fc->streams[i]->id == frag->track_id) {
> @@ -4294,6 +4295,10 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>      offset = frag->base_data_offset + data_offset;
>      distance = 0;
>      av_log(c->fc, AV_LOG_TRACE, "first sample flags 0x%x\n", first_sample_flags);
> +
> +    if (st->nb_index_entries)
> +        last_index_entry = &st->index_entries[st->nb_index_entries-1];
> +
>      for (i = 0; i < entries && !pb->eof_reached; i++) {
>          unsigned sample_size = frag->size;
>          int sample_flags = i ? frag->flags : first_sample_flags;
> @@ -4302,6 +4307,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>          int keyframe = 0;
>          int ctts_index = 0;
>          int old_nb_index_entries = st->nb_index_entries;
> +        int index_entry_flags = 0;
>  
>          if (flags & MOV_TRUN_SAMPLE_DURATION) sample_duration = avio_rb32(pb);
>          if (flags & MOV_TRUN_SAMPLE_SIZE)     sample_size     = avio_rb32(pb);
> @@ -4338,10 +4344,16 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>              keyframe =
>                  !(sample_flags & (MOV_FRAG_SAMPLE_FLAG_IS_NON_SYNC |
>                                    MOV_FRAG_SAMPLE_FLAG_DEPENDS_YES));
> -        if (keyframe)
> +        if (keyframe) {
>              distance = 0;
> +            index_entry_flags |= AVINDEX_KEYFRAME;
> +        }
> +        // Fragments can overlap in time.  Discard overlapping frames after
> +        // decoding.

> +        if (last_index_entry && last_index_entry->timestamp >= dts)

the memory last_index_entry points to can be reallocated in this loop
making the pointer invalid


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Does the universe only have a finite lifespan? No, its going to go on
forever, its just that you wont like living in it. -- Hiranya Peiri
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