[FFmpeg-devel] [PATCH 1/2] avformat/utils: Assert that stream_index is valid

[Gyan]

On 24-09-2019 10:01 PM, Andreas Rheinhardt wrote:
> There is currently an ordinary check for this (which would lead to a
> memleak), but given that no demuxer should ever return a packet with an
> invalid stream_index it is more appropriate for this to be an assert.
>
> FATE passes with this change.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>   libavformat/utils.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 3983a3f4ce..d8ef5fe54c 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -884,10 +884,8 @@ int ff_read_packet(AVFormatContext *s, AVPacket *pkt)
>               continue;
>           }
>   
> -        if (pkt->stream_index >= (unsigned)s->nb_streams) {
> -            av_log(s, AV_LOG_ERROR, "Invalid stream index %d\n", pkt->stream_index);
> -            continue;
> -        }
> +        av_assert0(pkt->stream_index < (unsigned)s->nb_streams &&
> +                   "Invalid stream index.\n");

The mpegts demuxer can send packets from new streams which appear 
mid-way. See the check in ffmpeg.c process_input() which discards these 
packets.
Whereas the patch will lead to an abort in fftools and other user apps 
transcoding a live feed.

Gyan