- encoding: set by libavcodec in avcodec_open2(). Each submitted frame
except the last must contain exactly frame_size samples per channel.
May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
frame size is not restricted.
- decoding: may be set by some decoders to indicate constant frame size
Number of samples per channel in an audio frame.
- encoding: set by libavcodec in avcodec_open2(). Each submitted frame except the last must contain exactly frame_size samples per channel. May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the frame size is not restricted. - decoding: may be set by some decoders to indicate constant frame size