FFmpeg av_read_frame not reading frames properly?

Question

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.

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.

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 isolate the end of file code?

Answer 1

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));

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

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

av_free_packet() has been deprecated, using av_packet_unref() instead, at the end of each av_read_frame() loop.

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

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.

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.