/* set up the offset and length to receive the current frequency.  */
static int prepare_playback_sync_urb(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime, struct urb *urb)
/* set up the offset and length to receive the current frequency.  */
static int prepare_playback_sync_urb(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime, struct urb *urb)
{
	struct snd_urb_ctx *ctx = urb->context;
	urb->dev = ctx->subs->dev;
	urb->iso_frame_desc[0].length = 3;
	urb->iso_frame_desc[0].offset = 0;
	return 0;
}