[alsa-devel] [PATCH v2] ALSA: usb: Work around CM6631 sample rate change bug
The C-Media CM6631 USB-to-S/PDIF receiver doesn't respond to changes in sample rate while the interface is active.
Reset the interface after setting the sampling frequency on sample rate changes, to ensure that the sample rate set by snd_usb_init_sample_rate() is used. Otherwise, the device will try to use the sample rate of the previous stream, causing distorted sound on sample rate changes.
Signed-off-by: Torstein Hegge hegge@resisty.net --- sound/usb/clock.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/sound/usb/clock.c b/sound/usb/clock.c index 5e634a2..d12a9c4 100644 --- a/sound/usb/clock.c +++ b/sound/usb/clock.c @@ -255,6 +255,7 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface, unsigned char data[4]; int err, crate; int clock = snd_usb_clock_find_source(chip, fmt->clock); + unsigned int previous_rate;
if (clock < 0) return clock; @@ -266,6 +267,18 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface, return -ENXIO; }
+ if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR, + USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN, + UAC2_CS_CONTROL_SAM_FREQ << 8, + snd_usb_ctrl_intf(chip) | (clock << 8), + data, sizeof(data))) < 0) { + snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq (v2)\n", + dev->devnum, iface, fmt->altsetting); + return err; + } + + previous_rate = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24); + data[0] = rate; data[1] = rate >> 8; data[2] = rate >> 16; @@ -294,6 +307,18 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface, if (crate != rate) snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);
+ /* Some devices doesn't respond to sample rate changes while the + * interface is active. */ + if (crate != previous_rate) { + switch (chip->usb_id) { + case USB_ID(0x0d8c, 0x0304): /* C-Media - Schiit USB */ + case USB_ID(0x0d8c, 0x0309): /* C-Media CM6631 */ + usb_set_interface(dev, iface, 0); + usb_set_interface(dev, iface, fmt->altsetting); + break; + } + } + return 0; }
Hi
Some comments:
On 4 Mar 2013 23:40, "Torstein Hegge" hegge@resisty.net wrote:
The C-Media CM6631 USB-to-S/PDIF receiver doesn't respond to changes in sample rate while the interface is active.
Reset the interface after setting the sampling frequency on sample rate changes, to ensure that the sample rate set by snd_usb_init_sample_rate()
is
used. Otherwise, the device will try to use the sample rate of the
previous
stream, causing distorted sound on sample rate changes.
Signed-off-by: Torstein Hegge hegge@resisty.net
sound/usb/clock.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/sound/usb/clock.c b/sound/usb/clock.c index 5e634a2..d12a9c4 100644 --- a/sound/usb/clock.c +++ b/sound/usb/clock.c @@ -255,6 +255,7 @@ static int set_sample_rate_v2(struct snd_usb_audio
*chip, int iface,
unsigned char data[4]; int err, crate; int clock = snd_usb_clock_find_source(chip, fmt->clock);
unsigned int previous_rate;
crate and previous_rate are different types. Why don't call it prate or change both name?
if (clock < 0) return clock;@@ -266,6 +267,18 @@ static int set_sample_rate_v2(struct snd_usb_audio
*chip, int iface,
return -ENXIO; }
if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),
UAC2_CS_CUR,
Is it more clear to assign it and then test?
USB_TYPE_CLASS | USB_RECIP_INTERFACE |
USB_DIR_IN,
UAC2_CS_CONTROL_SAM_FREQ << 8,snd_usb_ctrl_intf(chip) | (clock << 8),data, sizeof(data))) < 0) {snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq
(v2)\n",
dev->devnum, iface, fmt->altsetting);return err;}previous_rate = data[0] | (data[1] << 8) | (data[2] << 16) |
(data[3] << 24);
data[0] = rate; data[1] = rate >> 8; data[2] = rate >> 16;@@ -294,6 +307,18 @@ static int set_sample_rate_v2(struct snd_usb_audio
*chip, int iface,
if (crate != rate) snd_printd(KERN_WARNING "current rate %d is different
from the runtime rate %d\n", crate, rate);
/* Some devices doesn't respond to sample rate changes while the* interface is active. */if (crate != previous_rate) {switch (chip->usb_id) {case USB_ID(0x0d8c, 0x0304): /* C-Media - Schiit USB */case USB_ID(0x0d8c, 0x0309): /* C-Media CM6631 */usb_set_interface(dev, iface, 0);usb_set_interface(dev, iface, fmt->altsetting);break;}}return 0;}
-- 1.7.10.4
Michael _______________________________________________
Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
On Tue, Mar 05, 2013 at 07:02:58AM +0100, Michael Trimarchi wrote:
Hi
Some comments:
On 4 Mar 2013 23:40, "Torstein Hegge" hegge@resisty.net wrote:
The C-Media CM6631 USB-to-S/PDIF receiver doesn't respond to changes in sample rate while the interface is active.
Reset the interface after setting the sampling frequency on sample rate changes, to ensure that the sample rate set by snd_usb_init_sample_rate()
is
used. Otherwise, the device will try to use the sample rate of the
previous
stream, causing distorted sound on sample rate changes.
Signed-off-by: Torstein Hegge hegge@resisty.net
sound/usb/clock.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/sound/usb/clock.c b/sound/usb/clock.c index 5e634a2..d12a9c4 100644 --- a/sound/usb/clock.c +++ b/sound/usb/clock.c @@ -255,6 +255,7 @@ static int set_sample_rate_v2(struct snd_usb_audio
*chip, int iface,
unsigned char data[4]; int err, crate; int clock = snd_usb_clock_find_source(chip, fmt->clock);
unsigned int previous_rate;crate and previous_rate are different types. Why don't call it prate or change both name?
How about int cur_rate, prev_rate; ?
if (clock < 0) return clock;@@ -266,6 +267,18 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface, return -ENXIO; }
if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,Is it more clear to assign it and then test?
I agree that separate assign and test would be more readable, but this is consistent with the four other calls to snd_usb_ctl_msg() in clock.c.
Torstein
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Michael Trimarchi -
Torstein Hegge