[FFmpeg-devel] [PATCH 2/3] avcodec/h264_picture: add ff_h264_replace_picture()

[James Almer]

On 8/8/2021 8:16 PM, Andreas Rheinhardt wrote:
> James Almer:
>> Will remove unnecessary allocations when both src and dst picture contain
>> references to the same buffers.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   libavcodec/h264_picture.c | 45 +++++++++++++++++++++++++++++++++++++++
>>   libavcodec/h264dec.h      |  1 +
>>   2 files changed, 46 insertions(+)
>>
>> diff --git a/libavcodec/h264_picture.c b/libavcodec/h264_picture.c
>> index 89aef37edd..1073d9e7e0 100644
>> --- a/libavcodec/h264_picture.c
>> +++ b/libavcodec/h264_picture.c
>> @@ -142,6 +142,51 @@ fail:
>>       return ret;
>>   }
>>   
>> +int ff_h264_replace_picture(H264Context *h, H264Picture *dst, H264Picture *src)
> 
> Is there something that hinders you from making src const? If so, I
> don't see it.

Amended locally (Also h264_copy_picture_params() in patch 1/3).

> 
> 
>> +{
>> +    int ret, i;
>> +
>> +    if (!src->f || !src->f->buf[0]) {
>> +        ff_h264_unref_picture(h, dst);
>> +        return 0;
>> +    }
>> +
>> +    av_assert0(src->tf.f == src->f);
>> +
>> +    dst->tf.f = dst->f;
>> +    ff_thread_release_buffer(h->avctx, &dst->tf);
>> +    ret = ff_thread_ref_frame(&dst->tf, &src->tf);
>> +    if (ret < 0)
>> +        goto fail;
>> +
>> +    ret  = av_buffer_replace(&dst->qscale_table_buf, src->qscale_table_buf);
>> +    ret |= av_buffer_replace(&dst->mb_type_buf, src->mb_type_buf);
>> +    ret |= av_buffer_replace(&dst->pps_buf, src->pps_buf);
>> +    if (ret < 0)
>> +        goto fail;
>> +
>> +    for (i = 0; i < 2; i++) {
>> +        ret  = av_buffer_replace(&dst->motion_val_buf[i], src->motion_val_buf[i]);
>> +        ret |= av_buffer_replace(&dst->ref_index_buf[i], src->ref_index_buf[i]);
>> +        if (ret < 0)
>> +            goto fail;
>> +    }
>> +
>> +    if (src->hwaccel_picture_private) {
> 
> dst in this function is allowed to be used/dirty; so I don't see
> anything that precludes dst->hwaccel_picture_private/hwaccel_priv_buf to
> be set while the same is not true for src. But then this check means
> that dst is not equivalent to src.
> 
>> +        ret = av_buffer_replace(&dst->hwaccel_priv_buf, src->hwaccel_priv_buf);
>> +        if (ret < 0)
>> +            goto fail;
>> +        dst->hwaccel_picture_private = dst->hwaccel_priv_buf->data;
> 
> This is the only thing that needs to be under if.

Amended locally into:

>     ret = av_buffer_replace(&dst->hwaccel_priv_buf, src->hwaccel_priv_buf);
>     if (ret < 0)
>         goto fail;
> 
>     dst->hwaccel_picture_private = NULL;
>     if (src->hwaccel_picture_private)
>         dst->hwaccel_picture_private = dst->hwaccel_priv_buf->data;

> 
> - Andreas
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