Re: [FFmpeg-devel] [PATCH 11/13] ffv1dec: reference the current packet into the main context

[Lynne <dev@lynne.ee>]

On 10/03/2025 18:42, Lynne wrote:
> On 10/03/2025 04:14, Andreas Rheinhardt wrote:
>> Lynne:
>>> ---
>>>   libavcodec/ffv1.h    |  3 +++
>>>   libavcodec/ffv1dec.c | 19 +++++++++++++++++--
>>>   2 files changed, 20 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavcodec/ffv1.h b/libavcodec/ffv1.h
>>> index 8c0e71284d..860a5c14b1 100644
>>> --- a/libavcodec/ffv1.h
>>> +++ b/libavcodec/ffv1.h
>>> @@ -174,6 +174,9 @@ typedef struct FFV1Context {
>>>        * NOT shared between frame threads.
>>>        */
>>>       uint8_t           frame_damaged;
>>> +
>>> +    /* Reference to the current packet */
>>> +    AVPacket *pkt_ref;
>>>   } FFV1Context;
>>>   int ff_ffv1_common_init(AVCodecContext *avctx, FFV1Context *s);
>>> diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
>>> index eaa21eebdf..6396f22f79 100644
>>> --- a/libavcodec/ffv1dec.c
>>> +++ b/libavcodec/ffv1dec.c
>>> @@ -469,6 +469,10 @@ static av_cold int decode_init(AVCodecContext 
>>> *avctx)
>>>       f->pix_fmt = AV_PIX_FMT_NONE;
>>>       f->configured_pix_fmt = AV_PIX_FMT_NONE;
>>> +    f->pkt_ref = av_packet_alloc();
>>> +    if (!f->pkt_ref)
>>> +        return AVERROR(ENOMEM);
>>> +
>>>       if ((ret = ff_ffv1_common_init(avctx, f)) < 0)
>>>           return ret;
>>> @@ -701,6 +705,10 @@ static int decode_frame(AVCodecContext *avctx, 
>>> AVFrame *rframe,
>>>       /* Start */
>>>       if (hwaccel) {
>>> +        ret = av_packet_ref(f->pkt_ref, avpkt);
>>> +        if (ret < 0)
>>> +            return ret;
>>> +
>>>           ret = hwaccel->start_frame(avctx, avpkt->data, avpkt->size);
>>>           if (ret < 0)
>>>               return ret;
>>> @@ -720,15 +728,21 @@ static int decode_frame(AVCodecContext *avctx, 
>>> AVFrame *rframe,
>>>               uint32_t len;
>>>               ret = find_next_slice(avctx, avpkt->data, buf_end, i,
>>>                                     &pos, &len);
>>> -            if (ret < 0)
>>> +            if (ret < 0) {
>>> +                av_packet_unref(f->pkt_ref);
>>>                   return ret;
>>> +            }
>>>               buf_end -= len;
>>>               ret = hwaccel->decode_slice(avctx, pos, len);
>>> -            if (ret < 0)
>>> +            if (ret < 0) {
>>> +                av_packet_unref(f->pkt_ref);
>>>                   return ret;
>>> +            }
>>>           }
>>> +
>>> +        av_packet_unref(f->pkt_ref);
>>>       } else {
>>>           ret = decode_slices(avctx, c, avpkt);
>>>           if (ret < 0)
>>> @@ -827,6 +841,7 @@ static av_cold int 
>>> ffv1_decode_close(AVCodecContext *avctx)
>>>       ff_progress_frame_unref(&s->last_picture);
>>>       av_refstruct_unref(&s->hwaccel_last_picture_private);
>>> +    av_packet_free(&s->pkt_ref);
>>>       ff_ffv1_close(s);
>>>       return 0;
>>
>> Why not simply use a const AVPacket*?
> 
> No reason. Fixed locally.
> Thanks.

*reverted this change.
We need to ref the packet, since we map its memory and let the GPU use 
it directly without copying the contents. 6k16bit content at 24fps is 
typically around 2Gbps when compressed, so avoiding copies is important.
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