[FFmpeg-devel] [PATCH v2 1/5] fftools/ffmpeg_demux: honor -ch_layout options for overriding input stream channel layout

[Marton Balint]

On Sun, 19 May 2024, Marton Balint wrote:

> The code only set the channel layout of the AVFormatContext, so the user could
> not override the channel layout if the demuxer did not have such parameter.
>
> This used to work via the respective AVCodecContext option, but since
> 639c2f00497257cb60ecaeeac1aacfa80df3be06 it no longer gets passed to the
> decoders. It is actually better if we set it manually, instead of using the
> codec option because that way we can also override it on the stream level, so
> it will also work for stream copy or bitstream filtering.
>
> We don't allow changing the number of channels, because that can cause
> unexpected results. We disable layout guessing, if a channel layout is
> specified.
>
> Fixes ticket #11016.

Will apply the series.

Regards,
Marton

>
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
> fftools/ffmpeg_demux.c | 27 ++++++++++++++++++++++++---
> 1 file changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
> index cba63dab5f..1ca8d804ae 100644
> --- a/fftools/ffmpeg_demux.c
> +++ b/fftools/ffmpeg_demux.c
> @@ -1386,9 +1386,30 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st)
>
>         break;
>     case AVMEDIA_TYPE_AUDIO: {
> -        int guess_layout_max = INT_MAX;
> -        MATCH_PER_STREAM_OPT(guess_layout_max, i, guess_layout_max, ic, st);
> -        guess_input_channel_layout(ist, par, guess_layout_max);
> +        char *ch_layout_str = NULL;
> +        MATCH_PER_STREAM_OPT(audio_ch_layouts, str, ch_layout_str, ic, st);
> +        if (ch_layout_str) {
> +            AVChannelLayout ch_layout;
> +            ret = av_channel_layout_from_string(&ch_layout, ch_layout_str);
> +            if (ret < 0) {
> +                av_log(ist, AV_LOG_ERROR, "Error parsing channel layout %s.\n", ch_layout_str);
> +                return ret;
> +            }
> +            if (par->ch_layout.nb_channels <= 0 || par->ch_layout.nb_channels == ch_layout.nb_channels) {
> +                av_channel_layout_uninit(&par->ch_layout);
> +                par->ch_layout = ch_layout;
> +            } else {
> +                av_log(ist, AV_LOG_ERROR,
> +                    "Specified channel layout '%s' has %d channels, but input has %d channels.\n",
> +                    ch_layout_str, ch_layout.nb_channels, par->ch_layout.nb_channels);
> +                av_channel_layout_uninit(&ch_layout);
> +                return AVERROR(EINVAL);
> +            }
> +        } else {
> +            int guess_layout_max = INT_MAX;
> +            MATCH_PER_STREAM_OPT(guess_layout_max, i, guess_layout_max, ic, st);
> +            guess_input_channel_layout(ist, par, guess_layout_max);
> +        }
>         break;
>     }
>     case AVMEDIA_TYPE_DATA:
> -- 
> 2.35.3
>
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