ffmpeg 文档中这样描述
got_picture_ptr Zero if no frame could be decompressed, otherwise, it is nonzero.
ask :
(ffmpeg avcodec_decode_video) what does the value got_picture_ptr mean ,
i found it is a random num after function avcodec_decode_video()
answer;
for almost codecs:
*got_picture_ptr = sizeof(AVFrame);
It is just a flag to notice a frame ready!