如果我的FFmpeg使用av_read_frame多帧丢失 [英] Multiple frames lost if I use av_read_frame in FFmpeg

问题描述

我有3500帧的HEVC序列和我写的去codeR阅读（通过阅读框架和转储到YUV）。在我的main（），我有一个for循环，调用去codeR（）3500次（我假设在这个阶段，在main（）知道有多少帧有）。

I have an HEVC sequence with 3500 frames and I am writing a decoder for reading it (read frame by frame and dump to yuv). In my main(), I have a for loop that calls a decoder() 3500 times (I am assuming at this stage that the main() knows how many frames there are).

因此​​，每次调用去codeR（），我需要返回一个完整的框架。这就是德codeR（）看起来像..

So, for every call to decoder(), I need a complete frame to be returned. This is what the decoder() looks like..

bool decode(pFormatCtx, pCodecCtx)
{
    int gotaFrame=0;

    while (gotaFrame==0) {

        printf("1\t");

        if ( !av_read_frame(pFormatCtx, &packet) ) { 
            if(packet.stream_index==videoStreamIndex) {

                // try decoding
                avcodec_decode_video2(pCodecCtx, pFrame, &gotaFrame, &packet);

                if (gotaFrame) {  // decode success.

                    printf("2\t");

                    // dump to yuv ... not shown here. 

                    // cleanup
                    av_frame_unref(pFrame);
                    av_frame_free(&pFrame);
                    av_free_packet(&packet);

                    return true;
                }
            }
        }
    }
}

该行为是这样的：1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 ......看起来它解码一个之前读取几个帧？第一帧是一个I帧，所以不应该说是德codeD上吗？

The behavior is like this: 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 ...... it looks like it reads several frames before decoding one? The first frame is an I-frame, so shouldn't that be decoded right away?

有了这个code，我最终失去了几帧（由一系列1秒表示）。有人可以帮助我在这里？有什么我在我的code做错了吗？

With this code, I end up losing the several frames (indicated by the series of 1s). Can someone help me out here? Is there something I am doing wrong in my code?

更新：测试剪辑视频而已。没有音讯。

Update: the test clip is video-only. No audio.

推荐答案

你们看到的是正确的行为。去codeR bufferers多线程效率的几帧。它可能需要几个帧以黄金泵，因为它是。基本上，让你的程序反应灵敏，AV codec_de code_video2排队解码框架，然后返回。这prevents阻塞很长一段时间你的程序。它也绝对需要以延迟在B帧的情况下，其中，所述去code顺序可能不是相同的显示顺序解码

What you are seeing is the correct behavior. The decoder bufferers a few frames for multithreaded efficiency. And it may take several frames to 'prime the pump' as it were. Basically, to keep your program responsive, avcodec_decode_video2 queues up the frame for decoding, then returns. This prevents your program from blocking for a long time. It is also absolutely required to delay decoding in the case of B frames where the decode order may not be the same as the display order.

那么，如何才能不失去这些框架？ av_read_frame停止回新框架后，必须通过调用AV codec_de code_video2空数据包，直到没有更多的帧重新调整冲去$ C $铬。

So, how to not lose these frames? After av_read_frame stops returning new frames, you must flush the decoder by calling avcodec_decode_video2 with empty packets until no more frames are retuned.

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