Re: [FFmpeg-devel] [PATCH 1/4] avformat/demux: don't propagate unsupported skip samples packet side data values

[James Almer <jamrial@gmail.com>]

On 1/31/2022 10:56 PM, James Almer wrote:
> Should fix ticket #9622
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
> I'm not sure if this is ok or not. The AV_PKT_DATA_SKIP_SAMPLES doxy states
> the skip samples value is a little endian uint32 value, so even if the mov
> demuxer wrote a truncated int64_t value in sti->skip_samples (which, being an
> int, can be negative), it would still be "valid" when written into the packet
> as side data.
> 
> Chromium's fix is https://chromium-review.googlesource.com/c/chromium/src/+/3424556
> where you can see they have been reading the skip samples value from
> AV_PKT_DATA_SKIP_SAMPLES as an int.
> 
>   libavformat/demux.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/libavformat/demux.c b/libavformat/demux.c
> index f895f0ba85..09d539af68 100644
> --- a/libavformat/demux.c
> +++ b/libavformat/demux.c
> @@ -1354,6 +1354,7 @@ static int read_frame_internal(AVFormatContext *s, AVPacket *pkt)
>           }
>           if (sti->start_skip_samples && (pkt->pts == 0 || pkt->pts == RELATIVE_TS_BASE))
>               sti->skip_samples = sti->start_skip_samples;
> +        sti->skip_samples = FFMAX(0, sti->skip_samples);
>           if (sti->skip_samples || discard_padding) {
>               uint8_t *p = av_packet_new_side_data(pkt, AV_PKT_DATA_SKIP_SAMPLES, 10);
>               if (p) {

Will apply patchset.
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