[FFmpeg-devel] [PATCH] ffmpeg: add option recast_media

[Anton Khirnov]

Quoting Gyan Doshi (2021-07-02 12:03:05)
> Allows forcing decoders of different media type.
> Needed to decode media data muxed as data streams.
> ---
>  doc/ffmpeg.texi      | 5 +++++
>  fftools/ffmpeg_opt.c | 7 ++++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
> index 7827291755..c1065086e5 100644
> --- a/doc/ffmpeg.texi
> +++ b/doc/ffmpeg.texi
> @@ -449,6 +449,11 @@ output file already exists.
>  Set number of times input stream shall be looped. Loop 0 means no loop,
>  loop -1 means infinite loop.
>  
> + at item -recast_media (@emph{global})
> +Enable to allow forcing a decoder of a different media type than
> +the one detected or designated by the demuxer. Useful for decoding
> +media data muxed as data streams.
> +
>  @item -c[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
>  @itemx -codec[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
>  Select an encoder (when used before an output file) or a decoder (when used
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index a63bed54cf..76a220c21c 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -186,6 +186,7 @@ static int input_sync;
>  static int input_stream_potentially_available = 0;
>  static int ignore_unknown_streams = 0;
>  static int copy_unknown_streams = 0;
> +static int recast_media = 0;
>  static int find_stream_info = 1;
>  
>  static void uninit_options(OptionsContext *o)
> @@ -759,7 +760,7 @@ static const AVCodec *find_codec_or_die(const char *name, enum AVMediaType type,
>          av_log(NULL, AV_LOG_FATAL, "Unknown %s '%s'\n", codec_string, name);
>          exit_program(1);
>      }
> -    if (codec->type != type) {
> +    if (codec->type != type && !recast_media) {
>          av_log(NULL, AV_LOG_FATAL, "Invalid %s type '%s'\n", codec_string, name);
>          exit_program(1);
>      }
> @@ -774,6 +775,8 @@ static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVSt
>      if (codec_name) {
>          const AVCodec *codec = find_codec_or_die(codec_name, st->codecpar->codec_type, 0);
>          st->codecpar->codec_id = codec->id;
> +        if (recast_media && st->codecpar->codec_type != codec->type)
> +            st->codecpar->codec_type = codec->type;

The caller is not allowed to modify this struct for demuxing. This might
confuse demuxers that expect the values they put there to remain

-- 
Anton Khirnov