FFmpeg av_read_frame无法正确读取帧? [英] FFmpeg av_read_frame not reading frames properly?

问题描述

好的，所以我下载了.yuv格式的一些原始UHD序列，并在.mp4容器中以ffmpeg对其进行了编码(h264 4:4:4，100％质量，25fps).当我使用ffprobe找出要编码的帧数时，我得到600，所以这是24秒的视频.

Alright, so I've downloaded some raw UHD sequences in .yuv format and encoded them with ffmpeg in .mp4 container (h264 4:4:4, 100% quality, 25fps). When i use ffprobe to find out how many frames are encoded i get 600, so that's 24 secs of video.

但是，当我通过 av_read_frame 运行那些编码的视频序列时，在 av_read_frame 返回错误代码 -12 <之前，我只能得到40-50％的已处理帧/code>.因此，我很疯狂地猜测，流中间有一些数据包会被 av_read_frame 读取，并迫使函数返回 -12 .

BUT, when i run those encoded video sequences through av_read_frame i only get like 40-50% of frames processed before av_read_frame returns error code -12. So I'm wild guessing that there are some data packages in middle of the streams which get read by av_read_frame and forces a function to return -12.

我的问题是什么，我应该如何处理此问题，以便可以编码完整的帧数(600)?当 av_read_frame 返回不同于 0 的值时，我应该 av_free_packet 并继续读取下一帧吗?由于 av_read_frame 返回值<0 用于错误代码，哪个错误代码用于 EOF ，以便我可以隔离文件代码的末尾?

What my questions are, how should i deal with this problem so i can encode full number of frames (600)? When av_read_frame returns value different from 0 should i av_free_packet and proceed to read next frame? Since av_read_frame returns values < 0 for error codes, which error code is used for EOF so i can insulate end of file code?

推荐答案

尽管很难说出解码出了什么问题，但 -12 仍然不是一个不可理解的神奇数字.

Though it's difficult to say what's wrong with your decoding, still -12 is not a magic number that can't be understood.

printf("%s\n", av_err2str(-12));

这将打印无法分配内存，这是这里的真正问题.

This will print Cannot allocate memory, which is the real problem here.

从 av_read_frame()获得正返回值时，可以继续进行.

And when getting a positive return value from av_read_frame(), it's ok to go on.

av_free_packet().

while(av_read_frame(fmt_ctx, &pkt) >= 0) {
    // decode packet and other stuff
    av_packet_unref(&pkt); 
}

最后，通常无需担心EOF，因为 av_decode_video2()或其他解码函数会将int参数设置为适当的值，以指示是否存在要解压缩的帧.

At last, usually there's no need to worry about EOF, since av_decode_video2() or other decode functions will set a int parameter to proper value indicating whether there is frame to be decompressed.

如果您使用的是较新的ffmpeg(> = 3.1)解码/编码API或确实需要处理EOF，请将返回值与 AVERROR_EOF 进行比较.

If you're using a rather new ffmpeg(>=3.1) decoding/encoding API or really need to deal with EOF, compare the return value with AVERROR_EOF.

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