ffmpeg 之avcodec_receive_frame分析二

约定不等于承诺〃 2023-01-15 03:56 125阅读 0赞

直接看代码，我们在一中分析到，在send的时候最后一步就是将gpu中数据拷贝出来（这个过程是异步的），然后在这里读取

int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
    { 
        AVCodecInternal *avci = avctx->internal;
        int ret, changed;
    
        av_frame_unref(frame);
    
        if (!avcodec_is_open(avctx) || !av_codec_is_decoder(avctx->codec))
            return AVERROR(EINVAL);
    
        if (avci->buffer_frame->buf[0]) { 
            av_frame_move_ref(frame, avci->buffer_frame);
        } else { 
        //在这里接受数据
            ret = decode_receive_frame_internal(avctx, frame);
            if (ret < 0)
                return ret;
        }
    
        if (avctx->codec_type == AVMEDIA_TYPE_VIDEO) { 
            ret = apply_cropping(avctx, frame);
            if (ret < 0) { 
                av_frame_unref(frame);
                return ret;
            }
        }
    
        avctx->frame_number++;
    
        if (avctx->flags & AV_CODEC_FLAG_DROPCHANGED) { 
    
            if (avctx->frame_number == 1) { 
                avci->initial_format = frame->format;
                switch(avctx->codec_type) { 
                case AVMEDIA_TYPE_VIDEO:
                    avci->initial_width  = frame->width;
                    avci->initial_height = frame->height;
                    break;
                case AVMEDIA_TYPE_AUDIO:
                    avci->initial_sample_rate = frame->sample_rate ? frame->sample_rate :
                                                                     avctx->sample_rate;
                    avci->initial_channels       = frame->channels;
                    avci->initial_channel_layout = frame->channel_layout;
                    break;
                }
            }
    
            if (avctx->frame_number > 1) { 
                changed = avci->initial_format != frame->format;
    
               switch(avctx->codec_type) { 
                case AVMEDIA_TYPE_VIDEO:
                    changed |= avci->initial_width  != frame->width ||
                               avci->initial_height != frame->height;
                    break;
                case AVMEDIA_TYPE_AUDIO:
                    changed |= avci->initial_sample_rate    != frame->sample_rate ||
                               avci->initial_sample_rate    != avctx->sample_rate ||
                               avci->initial_channels       != frame->channels ||
                               avci->initial_channel_layout != frame->channel_layout;
                    break;
                }
    
                if (changed) { 
                    avci->changed_frames_dropped++;
                    av_log(avctx, AV_LOG_INFO, "dropped changed frame #%d pts %"PRId64
                                                " drop count: %d \n",
                                                avctx->frame_number, frame->pts,
                                                avci->changed_frames_dropped);
                    av_frame_unref(frame);
                    return AVERROR_INPUT_CHANGED;
                }
            }
        }
        return 0;
    }
    
    
    
    static int decode_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
    { 
        AVCodecInternal *avci = avctx->internal;
        int ret;
    
        av_assert0(!frame->buf[0]);
    
        if (avctx->codec->receive_frame)
        //在这里执行
            ret = avctx->codec->receive_frame(avctx, frame);
        else
            ret = decode_simple_receive_frame(avctx, frame);
    
        if (ret == AVERROR_EOF)
            avci->draining_done = 1;
    
        if (!ret) { 
            /* the only case where decode data is not set should be decoders * that do not call ff_get_buffer() */
            av_assert0((frame->private_ref && frame->private_ref->size == sizeof(FrameDecodeData)) ||
                       !(avctx->codec->capabilities & AV_CODEC_CAP_DR1));
    
            if (frame->private_ref) { 
                FrameDecodeData *fdd = (FrameDecodeData*)frame->private_ref->data;
    
                if (fdd->post_process) { 
                    ret = fdd->post_process(avctx, frame);
                    if (ret < 0) { 
                        av_frame_unref(frame);
                        return ret;
                    }
                }
            }
        }
    
        /* free the per-frame decode data */
        av_buffer_unref(&frame->private_ref);
    
        return ret;
    }