/**
* Initialize AVAudioResampleContext.
* @note The context must be configured using the AVOption API.
+ * @note The fields "in_channel_layout", "out_channel_layout",
+ * "in_sample_rate", "out_sample_rate", "in_sample_fmt",
+ * "out_sample_fmt" must be set.
*
* @see av_opt_set_int()
* @see av_opt_set_dict()
+ * @see av_get_default_channel_layout()
*
* @param avr audio resample context
* @return 0 on success, negative AVERROR code on failure