/* fill the length and offset of each urb descriptor. the fixed 10.14 frequency is passed through the pipe.  */
static int prepare_capture_sync_urb(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime, struct urb *urb)
/* fill the length and offset of each urb descriptor. the fixed 10.14 frequency is passed through the pipe.  */
static int prepare_capture_sync_urb(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime, struct urb *urb)
{
	unsigned char *cp = urb->transfer_buffer;
	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;
	cp[0] = subs->freqn >> 2;
	cp[1] = subs->freqn >> 10;
	cp[2] = subs->freqn >> 18;
	return 0;
}