[FFmpeg-devel] [PATCH] fftools/ffmpeg: Fallback to duration if sample rate is unavailable

[wm4]

On Tue,  1 May 2018 22:44:07 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> Regression since: af1761f7
> Fixes: Division by 0
> Fixes: ffmpeg_crash_1
> 
> Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  fftools/ffmpeg.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> index 5dc198f933..15fa54f24e 100644
> --- a/fftools/ffmpeg.c
> +++ b/fftools/ffmpeg.c
> @@ -2706,8 +2706,12 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
>          ist->dts = ist->next_dts;
>          switch (ist->dec_ctx->codec_type) {
>          case AVMEDIA_TYPE_AUDIO:
> -            ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
> -                             ist->dec_ctx->sample_rate;
> +            if (ist->dec_ctx->sample_rate) {
> +                ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
> +                                  ist->dec_ctx->sample_rate;
> +            } else {
> +                ist->next_dts += av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
> +            }
>              break;
>          case AVMEDIA_TYPE_VIDEO:
>              if (ist->framerate.num) {

Wouldn't it be better to error out here, instead of using yet another
unreliable value and "hoping for the best"?

Also I'm not sure, but I think unknown durations are sometimes set to
-1 instead of 0.