[FFmpeg-devel] [PATCH] avformat/utils: fix crashes in has_decode_delay_been_guessed

[wm4]

On Fri,  2 Dec 2016 13:51:24 +0100
Timo Rothenpieler <timo at rothenpieler.org> wrote:

> These paths can be taken when the actual underlying codec is not h264,
> but the user forces, for example via ffmpeg command line, a specific
> input decoder that happens to be a h264 decoder.
> 
> In that case, the codecpar codec_id is set to h264, but the internal
> avctx is the one of, for example, an mpeg2 decoder, thus crashing in
> this function.
> 
> Checking for the codec actually being h264 is not strictly neccesary to
> fix the crash, but a precaution to catch potential other unexpected
> codepaths.
> 
> Fixes #5985
> ---
>  libavformat/utils.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 345bbfe5fe..8e23c0c6ec 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -966,11 +966,14 @@ static int is_intra_only(enum AVCodecID id)
>  
>  static int has_decode_delay_been_guessed(AVStream *st)
>  {
> -    if (st->codecpar->codec_id != AV_CODEC_ID_H264) return 1;
> +    if (st->codecpar->codec_id != AV_CODEC_ID_H264 ||
> +       st->internal->avctx->codec_id != AV_CODEC_ID_H264)
> +        return 1;
>      if (!st->info) // if we have left find_stream_info then nb_decoded_frames won't increase anymore for stream copy
>          return 1;
>  #if CONFIG_H264_DECODER
> -    if (st->internal->avctx->has_b_frames &&
> +    if (st->internal->avctx->codec && !strcmp(st->internal->avctx->codec->name, "h264") &&
> +       st->internal->avctx->has_b_frames &&
>         avpriv_h264_has_num_reorder_frames(st->internal->avctx) == st->internal->avctx->has_b_frames)
>          return 1;
>  #endif

That looks ok, but: can someone explain to me why Libav does apparently
not need this shitshow?