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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: John S. Gruber <JohnSGruber@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
John S. Gruber 2009-12-27 12:19:58 -05:00 committed by Takashi Iwai
parent adc8d31326
commit 98e89f606c
2 changed files with 30 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
sound/usb/usbaudio.c
View File

@ -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 = frames * 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 */

1
sound/usb/usbaudio.h
View File

@ -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;