[FFmpeg-devel] [PATCH] avformat/apngenc: use the stream parameters extradata if no updated one is made available

[James Almer]

On 10/31/2016 11:32 PM, James Almer wrote:
> Fixes remuxing apng streams coming from the apng demuxer.
> This is a regression since 97792e85c338d129342f5812e2a52048373e57d6.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavformat/apngenc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/libavformat/apngenc.c b/libavformat/apngenc.c
> index e5e8aa9..2b88dcc 100644
> --- a/libavformat/apngenc.c
> +++ b/libavformat/apngenc.c
> @@ -101,6 +101,13 @@ static int apng_write_header(AVFormatContext *format_context)
>      avio_wb64(format_context->pb, PNGSIG);
>      // Remaining headers are written when they are copied from the encoder
>  
> +    apng->extra_data = av_mallocz(format_context->streams[0]->codecpar->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
> +    if (!apng->extra_data)
> +        return AVERROR(ENOMEM);
> +    apng->extra_data_size =  format_context->streams[0]->codecpar->extradata_size;
> +    memcpy(apng->extra_data, format_context->streams[0]->codecpar->extradata,
> +           format_context->streams[0]->codecpar->extradata_size);
> +

Alternatively we could just go back to the first version of Andreas' patch,
where the codecpar extradata was overwritten by the updated one from the
packet side data, and get rid of the private context buffer.

I assumed keeping the codecpar extradata intact was the correct behavior,
based on the avcodec.h documentation and since AVCodecParameters is an
intermediary struct meant to pass parameters between de/muxers and
de/encoders, but it seems the mov and flv muxers just overwrite it. I'm not
sure if it makes a difference at all.

Any opinions?