Re: [FFmpeg-devel] [PATCH] lavf/dash: Forward strict flag to component demuxers

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Frank Plowman:
> Before the patch, opening a DASH file containing streams which require
> experimental decoders was problematic.  No matter where the -strict -2
> was put on the command line, the option was not passed to the demuxer
> for that component.  This resulted in an error, prompting the user to
> add the -strict -2 flag, which is already present.  Decoding appeared to
> continue correctly however.
> 
> Patch removes the error message by creating an options object for the
> demuxer created for the component, which inherits from the parent
> demuxer.
> 
> Signed-off-by: Frank Plowman <post@frankplowman.com>
> ---
> PS: Can anyone think of other options which should be propagated to the
>     component demuxers?
> 
>  libavformat/dashdec.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
> index 555e21bf69..40abb5ebba 100644
> --- a/libavformat/dashdec.c
> +++ b/libavformat/dashdec.c
> @@ -1911,13 +1911,18 @@ static int reopen_demux_for_component(AVFormatContext *s, struct representation
>      if (ret < 0)
>          goto fail;
>      if (pls->n_fragments) {
> +        AVDictionary *stream_info_opts = NULL;
> +
>  #if FF_API_R_FRAME_RATE
>          if (pls->framerate.den) {
>              for (i = 0; i < pls->ctx->nb_streams; i++)
>                  pls->ctx->streams[i]->r_frame_rate = pls->framerate;
>          }
>  #endif
> -        ret = avformat_find_stream_info(pls->ctx, NULL);
> +
> +        av_dict_set_int(&stream_info_opts, "strict", s->strict_std_compliance, 0);
> +
> +        ret = avformat_find_stream_info(pls->ctx, &stream_info_opts);
>          if (ret < 0)
>              goto fail;
>      }

The loop over pls->ctx indicates that pls->ctx->nb_streams can be > 1
before avformat_find_stream_info(). But then using a single AVDictionary
is wrong, as avformat_find_stream_info() expects an array of
pls->ctx->nb_streams AVDictionary*.

Furthermore, the mixing between AVFormatContext and AVCodecContext
options here does not seem good (e.g. for ordinary demuxers setting
strict_std_compliance does not affect the AVCodecContext's values at all).

- Andreas

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