/* The following data should not be initialized. */
/**
- * Samples per packet, initialized when calling 'init'.
+ * 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 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
*/
int frame_size;