[FFmpeg-devel] [PATCH 1/2] avcodec/libx264: add a flush callback

[James Almer]

On 3/27/2023 5:33 PM, Andreas Rheinhardt wrote:
> James Almer:
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   libavcodec/libx264.c | 24 ++++++++++++++++++++++--
>>   1 file changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
>> index 92828fabc3..72c3b6cedc 100644
>> --- a/libavcodec/libx264.c
>> +++ b/libavcodec/libx264.c
>> @@ -178,8 +178,8 @@ static int encode_nals(AVCodecContext *ctx, AVPacket *pkt,
>>           memcpy(p, x4->sei, x4->sei_size);
>>           p += x4->sei_size;
>>           size -= x4->sei_size;
>> -        x4->sei_size = 0;
>> -        av_freep(&x4->sei);
>> +        /* Keep the value around in case of flush */
>> +        x4->sei_size = -x4->sei_size;
>>       }
>>   
>>       /* x264 guarantees the payloads of the NALs
>> @@ -648,6 +648,24 @@ FF_ENABLE_DEPRECATION_WARNINGS
>>       return 0;
>>   }
>>   
>> +static void X264_flush(AVCodecContext *avctx)
>> +{
>> +    X264Context *x4 = avctx->priv_data;
>> +    x264_nal_t *nal;
>> +    int nnal, ret;
>> +    x264_picture_t pic_out = {0};
>> +
>> +    do {
>> +        ret = x264_encoder_encode(x4->enc, &nal, &nnal, NULL, &pic_out);
>> +    } while (ret > 0 && x264_encoder_delayed_frames(x4->enc));
>> +
>> +    for (int i = 0; i < x4->nb_reordered_opaque; i++)
>> +        opaque_uninit(&x4->reordered_opaque[i]);
>> +
>> +    if (x4->sei_size < 0)
>> +        x4->sei_size = -x4->sei_size;
>> +}
>> +
>>   static av_cold int X264_close(AVCodecContext *avctx)
>>   {
>>       X264Context *x4 = avctx->priv_data;
>> @@ -1335,12 +1353,14 @@ FFCodec ff_libx264_encoder = {
>>       .p.capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY |
>>                           AV_CODEC_CAP_OTHER_THREADS |
>>                           AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE |
>> +                        AV_CODEC_CAP_ENCODER_FLUSH |
>>                           AV_CODEC_CAP_ENCODER_RECON_FRAME,
>>       .p.priv_class     = &x264_class,
>>       .p.wrapper_name   = "libx264",
>>       .priv_data_size   = sizeof(X264Context),
>>       .init             = X264_init,
>>       FF_CODEC_ENCODE_CB(X264_frame),
>> +    .flush            = X264_flush,
>>       .close            = X264_close,
>>       .defaults         = x264_defaults,
>>   #if X264_BUILD < 153
> 
> Wasn't AV_CODEC_CAP_ENCODER_FLUSH supposed to be only implemented for
> hardware encoders where closing and reopening an encoder is costly?
> 
> - Andreas

It was introduced thinking on those for the reason you mentioned, but 
there's nothing limiting its usage for other codecs.