[FFmpeg-devel] [PATCH] ffmpeg: always use single threaded decoding for attached pictures

[Hendrik Leppkes]

On Fri, Oct 6, 2017 at 10:14 PM, Marton Balint <cus at passwd.hu> wrote:
> Since af1761f7b5b1b72197dc40934953b775c2d951cc ffmpeg waits for a frame in each
> stream before writing the output header. If we are using threaded decoding for
> attached pictures, we have to read till EOF to be able to finally flush the
> decoder and output the decoded frame. This essentially makes ffmpeg buffer all
> non-attached picture packets, which will cause a "Too many packets buffered for
> output stream" eventually.
>
> By forcing single threaded decoding, we get a frame from a single packet as
> well and we can avoid the error.
>
> Fixes part of ticket #6375:
> ffmpeg -i 46564100.mp3 -acodec libmp3lame -ab 128k -ac 2 out.mp3
>
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  fftools/ffmpeg.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> index 5be8788ea8..6eb7bf9d84 100644
> --- a/fftools/ffmpeg.c
> +++ b/fftools/ffmpeg.c
> @@ -2909,6 +2909,9 @@ static int init_input_stream(int ist_index, char *error, int error_len)
>
>          if (!av_dict_get(ist->decoder_opts, "threads", NULL, 0))
>              av_dict_set(&ist->decoder_opts, "threads", "auto", 0);
> +        /* Attached pics are sparse, therefore we would not want to delay their decoding till EOF. */
> +        if (ist->st->disposition & AV_DISPOSITION_ATTACHED_PIC)
> +            av_dict_set(&ist->decoder_opts, "threads", "1", 0);
>

LGTM.

- Hendrik