* USB soundcard acting up
@ 2005-05-17 0:41 Peter Stuge
2005-05-17 7:54 ` Clemens Ladisch
0 siblings, 1 reply; 3+ messages in thread
From: Peter Stuge @ 2005-05-17 0:41 UTC (permalink / raw)
To: alsa-devel
[-- Attachment #1: Type: text/plain, Size: 2763 bytes --]
Hello,
I've built myself a simple USB soundcard from a PCM2902 TI chip and a
TosLink transmitter to avoid the sub-optimal DAC and signalling
environment in my laptop. The soundcard connects to my MD deck that I
either record on or just use as a DAC for playback.
The PCM2902 is a USB Audio Class device and the ALSA driver picks it
up without problems. It works well most of the time, but..
Now and then the MD deck unlocks for a fraction of a second, i.e.
loses sync in the digital input stream, which of course causes audio
to be lost.
Question is where the problem lies. It's not really reproducable, it
happens stochastically whether I'm actually playing audio or not. It
has happened with xmms OSS output+ALSA OSS emulation, xmms ALSA
output, alsaplayer and I believe once with mplayer too.
I have almost ruled out cabling completely, since I can remove the
optical cable from the transmitter and still have the MD lock to the
signal if I just hold the connector a few millimeters away from the
transmitter.
My circuit is a reference circuit straight from the data sheet,
connected to the reference circuit for the optical transmitter. Just
the chip and a handful passive components. Images at
http://cdy.org/~stuge/usnd/
I'm using ALSA compiled into the kernel, 2.6.11.7 right now and it
seems to happen less frequently here than with the 2.6.12rc:s that I
tried before. I've just compiled a 2.6.11.9 and will reboot into that
shortly.
Currently (2.6.11.7) :
$ cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version 1.0.8 (Thu Jan 13
09:39:32 2005 UTC).
$ cat /proc/asound/devices
8: [0- 0]: raw midi
18: [0- 2]: digital audio playback
17: [0- 1]: digital audio playback
16: [0- 0]: digital audio playback
24: [0- 0]: digital audio capture
0: [0- 0]: ctl
33: : timer
48: [1- 0]: digital audio playback
56: [1- 0]: digital audio capture
32: [1- 0]: ctl
$ cat /proc/asound/cards
0 [CS46xx ]: CS46xx - Sound Fusion CS46xx
Sound Fusion CS46xx at 0xe8122000/0xe8000000,
irq 9
1 [default ]: USB-Audio - USB Audio CODEC
Burr-Brown from TI USB Audio CODEC
at usb-0000:00:07.2-1.3, full
$ cat /proc/asound/pcm
00-00: CS46xx : CS46xx : playback 31 : capture 1
00-01: CS46xx - Rear : CS46xx - Rear : playback 31
00-02: CS46xx - IEC958 : CS46xx - IEC958 : playback 1
01-00: USB Audio : USB Audio : playback 1 : capture 1
Of course, I could use the 00-02 output instead, but I can't find a
connector for it on the laptop.
Anyway, does this sound at all like something related to ALSA? What
can I do to help debug? I know a fair bit of USB but haven't done
anything audio class before. lsusb -v output is attached.
Thanks for your time!
//Peter
[-- Attachment #2: lsusb-pcm2902.txt --]
[-- Type: text/plain, Size: 39716 bytes --]
Bus 001 Device 004: ID 08bb:2902 Texas Instruments Japan
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x08bb Texas Instruments Japan
idProduct 0x2902
bcdDevice 1.00
iManufacturer 1 Burr-Brown from TI
iProduct 2 USB Audio CODEC
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 1191
bNumInterfaces 4
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
MaxPower 100mA
Interface Descriptor:
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bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
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AudioControl Interface Descriptor:
bLength 10
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 1.00
wTotalLength 62
bInCollection 2
baInterfaceNr( 0) 1
baInterfaceNr( 1) 2
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bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0101 USB Streaming
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bNrChannels 2
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Left Front (L)
Right Front (R)
iChannelNames 0
iTerminal 0
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bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 2
wTerminalType 0x0301 Speaker
bAssocTerminal 0
bSourceID 3
iTerminal 0
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bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 3
bSourceID 1
bControlSize 1
bmaControls( 0) 0x01
Mute
bmaControls( 0) 0x02
Volume
bmaControls( 0) 0x02
Volume
iFeature 0
AudioControl Interface Descriptor:
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bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 4
wTerminalType 0x0201 Microphone
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bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 1
bDelay 0 frames
wFormatTag 1 PCM
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bLength 17
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
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bSubframeSize 2
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tSamFreq[ 1] 44100
tSamFreq[ 2] 48000
Endpoint Descriptor:
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bEndpointAddress 0x02 EP 2 OUT
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Endpoint Descriptor:
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bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 13
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
AudioControl Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 5
bDelay 0 frames
wFormatTag 1 PCM
AudioControl Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 2
bSubframeSize 1
bBitResolution 8
bSamFreqType 1 Discrete
tSamFreq[ 0] 8000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x84 EP 4 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
wMaxPacketSize 18
bInterval 1
bRefresh 0
bSynchAddress 0
AudioControl Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0 Decoded PCM samples
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 14
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
AudioControl Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 5
bDelay 0 frames
wFormatTag 1 PCM
AudioControl Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 1
bSubframeSize 1
bBitResolution 8
bSamFreqType 1 Discrete
tSamFreq[ 0] 8000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x84 EP 4 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
wMaxPacketSize 9
bInterval 1
bRefresh 0
bSynchAddress 0
AudioControl Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0 Decoded PCM samples
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 15
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
AudioControl Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 5
bDelay 0 frames
wFormatTag 1 PCM
AudioControl Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 2
bSubframeSize 2
bBitResolution 16
bSamFreqType 1 Discrete
tSamFreq[ 0] 11025
descriptor length past end: 09 05 84
Language IDs: (length=4)
0409 English(US)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: USB soundcard acting up
2005-05-17 0:41 USB soundcard acting up Peter Stuge
@ 2005-05-17 7:54 ` Clemens Ladisch
2005-05-17 15:05 ` Peter Stuge
0 siblings, 1 reply; 3+ messages in thread
From: Clemens Ladisch @ 2005-05-17 7:54 UTC (permalink / raw)
To: Peter Stuge; +Cc: alsa-devel
Peter Stuge wrote:
> The PCM2902 is a USB Audio Class device and the ALSA driver picks it
> up without problems. It works well most of the time, but..
>
> Now and then the MD deck unlocks for a fraction of a second, i.e.
> loses sync in the digital input stream, which of course causes audio
> to be lost.
>
> Question is where the problem lies. It's not really reproducable, it
> happens stochastically whether I'm actually playing audio or not.
That is, when you aren't playing anything, the device sends a stream
of silence which has the same glitches?
The output endpoints use adaptive synchronization, i.e., the PCM2902
is responsible for determining the exact rate of USB data, and
synchronizin to that. It may be possible that it thinks the sample
rate has changed, or that it can better approximate the USB data rate
by using a slightly different sample rate.
Does this happen at both 44.1 and 48 kHz? Synchronization at 44.1 kHz
isn't easy because packet sizes aren't constant, but at 48 kHz, the
driver sends exactly 48 samples per USB frame.
Regards,
Clemens
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: USB soundcard acting up
2005-05-17 7:54 ` Clemens Ladisch
@ 2005-05-17 15:05 ` Peter Stuge
0 siblings, 0 replies; 3+ messages in thread
From: Peter Stuge @ 2005-05-17 15:05 UTC (permalink / raw)
To: alsa-devel
(I'm on the list, please don't cc me. Thanks!)
Thanks for the reply!
On Tue, May 17, 2005 at 09:54:10AM +0200, Clemens Ladisch wrote:
> Peter Stuge wrote:
> > The PCM2902 is a USB Audio Class device and the ALSA driver picks it
> > up without problems. It works well most of the time, but..
> >
> > Now and then the MD deck unlocks for a fraction of a second, i.e.
> > loses sync in the digital input stream, which of course causes audio
> > to be lost.
> >
> > Question is where the problem lies. It's not really reproducable, it
> > happens stochastically whether I'm actually playing audio or not.
>
> That is, when you aren't playing anything, the device sends a stream
> of silence which has the same glitches?
Correct. This would indicate that the problem isn't really with ALSA,
but I figured someone on the list could provide insight from
experience with USB audio devices in general. :)
> The output endpoints use adaptive synchronization, i.e., the PCM2902
> is responsible for determining the exact rate of USB data, and
> synchronizin to that. It may be possible that it thinks the sample
> rate has changed, or that it can better approximate the USB data rate
> by using a slightly different sample rate.
Aha. I haven't read up on the Audio Class spec but I imagined there
was a command for selecting the sampling rate.
> Does this happen at both 44.1 and 48 kHz? Synchronization at 44.1
> kHz isn't easy because packet sizes aren't constant, but at 48 kHz,
> the driver sends exactly 48 samples per USB frame.
Right, I remember there was something special each 9th frame when
running at 44.1 from when I've looked in the audio class spec last.
But yes, it has happened at both rates. I've experimented back and
forth but haven't found any sure way to either reproduce or suppress
the problem.
Thanks for the input so far!
//Peter
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^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2005-05-17 15:05 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2005-05-17 0:41 USB soundcard acting up Peter Stuge
2005-05-17 7:54 ` Clemens Ladisch
2005-05-17 15:05 ` Peter Stuge
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