Re: [FFmpeg-devel] [PATCHv2 3/4] avcodec/svq1enc: output ident string in extradata field

[James Almer <jamrial@gmail.com>]

On 10/19/2022 10:30 PM, Peter Ross wrote:
> This will enable the acurate identification of FFmpeg produced
> SVQ1 streams, should there be new bugs found in the encoder.
> ---
>   libavcodec/svq1enc.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/libavcodec/svq1enc.c b/libavcodec/svq1enc.c
> index 9bd5a04368..6aacaef88d 100644
> --- a/libavcodec/svq1enc.c
> +++ b/libavcodec/svq1enc.c
> @@ -41,6 +41,7 @@
>   #include "svq1.h"
>   #include "svq1encdsp.h"
>   #include "svq1enc_cb.h"
> +#include "version.h"
>   
>   #include "libavutil/avassert.h"
>   #include "libavutil/frame.h"
> @@ -628,6 +629,14 @@ static av_cold int svq1_encode_init(AVCodecContext *avctx)
>   
>       ff_h263_encode_init(&s->m); // mv_penalty
>   
> +    if (!(s->avctx->flags & AV_CODEC_FLAG_BITEXACT)) {
> +        avctx->extradata = av_malloc(sizeof(LIBAVCODEC_IDENT));
> +        if (!avctx->extradata)
> +            return AVERROR(ENOMEM);
> +        memcpy(avctx->extradata, LIBAVCODEC_IDENT, sizeof(LIBAVCODEC_IDENT));
> +        avctx->extradata_size = sizeof(LIBAVCODEC_IDENT);

Can you explain what effect is this meant to have and where? Do or 
should muxers like mp4 and matroska expect extradata from svq1 streams 
that they are meant to write to the output file?

> +    }
> +
>       return 0;
>   }
>   
> 
> 
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