Commit 98e89f60 authored by John S. Gruber's avatar John S. Gruber Committed by Takashi Iwai
Browse files

ALSA: usb-audio: relax urb data align. restriction HVR-950Q and HVR-850 only 

Addressing audio quality problem.

In sound/usb/usbaudio.c, for the Hauppage HVR-950Q and HVR-850 only, change
retire_capture_urb to allow transfers on audio sub-slot boundaries rather
than audio slots boundaries.

With these devices the left and right channel samples can be split between
two different urbs. Throwing away extra channel samples causes a sound
quality problem for stereo streams as the left and right channels are
swapped repeatedly, perhaps many times per second.

Urbs unaligned on sub-slot boundaries are still truncated to the next
lowest stride (audio slot) to retain synchronization on samples even
though left/right channel synchronization may be lost in this case.

Detect the quirk using a case statement in snd_usb_audio_probe.

BugLink: https://bugs.launchpad.net/ubuntu/+bug/495745



Signed-off-by: default avatarJohn S. Gruber <JohnSGruber@gmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent adc8d313

sound/usb/usbaudio.c

+29 −2
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ struct snd_usb_substream { 
	unsigned int curpacksize;	/* current packet size in bytes (for capture) */

	unsigned int curframesize;	/* current packet size in frames (for capture) */

	unsigned int fill_max: 1;	/* fill max packet size always */

	unsigned int txfr_quirk:1;	/* allow sub-frame alignment */

	unsigned int fmt_type;		/* USB audio format type (1-3) */



	unsigned int running: 1;	/* running status */
@@ -353,14 +354,25 @@ static int retire_capture_urb(struct snd_usb_substream *subs, 
			snd_printd(KERN_ERR "frame %d active: %d\n", i, urb->iso_frame_desc[i].status);

			// continue;

		}

		frames = urb->iso_frame_desc[i].actual_length / stride;

		bytes = urb->iso_frame_desc[i].actual_length;

		frames = bytes / stride;

		if (!subs->txfr_quirk)

			bytes = frames * stride;

		if (bytes % (runtime->sample_bits >> 3) != 0) {

#ifdef CONFIG_SND_DEBUG_VERBOSE

			int oldbytes = bytes;

#endif

			bytes = frames * stride;

			snd_printdd(KERN_ERR "Corrected urb data len. %d->%d\n",

							oldbytes, bytes);

		}

		/* update the current pointer */

		spin_lock_irqsave(&subs->lock, flags);

		oldptr = subs->hwptr_done;

		subs->hwptr_done += bytes;

		if (subs->hwptr_done >= runtime->buffer_size * stride)

			subs->hwptr_done -= runtime->buffer_size * stride;

		frames = (bytes + (oldptr % stride)) / stride;

		subs->transfer_done += frames;

		if (subs->transfer_done >= runtime->period_size) {

			subs->transfer_done -= runtime->period_size;
@@ -2238,6 +2250,7 @@ static void init_substream(struct snd_usb_stream *as, int stream, struct audiofo 
	subs->stream = as;

	subs->direction = stream;

	subs->dev = as->chip->dev;

	subs->txfr_quirk = as->chip->txfr_quirk;

	if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL) {

		subs->ops = audio_urb_ops[stream];

	} else {
@@ -3618,6 +3631,20 @@ static void *snd_usb_audio_probe(struct usb_device *dev, 
		}

	}



	switch (chip->usb_id) {

	case USB_ID(0x2040, 0x7200): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7221): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7222): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7223): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7224): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7225): /* Hauppage hvr950Q */

	case USB_ID(0x2040, 0x7230): /* Hauppage hvr850 */

	case USB_ID(0x2040, 0x7250): /* Hauppage hvr950Q */

		chip->txfr_quirk = 1;

		break;

	default:

		chip->txfr_quirk = 0;

		}

	err = 1; /* continue */

	if (quirk && quirk->ifnum != QUIRK_NO_INTERFACE) {

		/* need some special handlings */

sound/usb/usbaudio.h

+1 −0
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ struct snd_usb_audio { 
	struct snd_card *card;

	u32 usb_id;

	int shutdown;

	unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */

	int num_interfaces;

	int num_suspended_intf;

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