Bug 9230

Summary: usbaudio microphone: regular sound distortion on several Logitech Webcams
Product: Drivers Reporter: Jörg Hermsdorf (funtasyspace)
Component: Sound(ALSA)Assignee: Jaroslav Kysela (perex)
Status: CLOSED DOCUMENTED    
Severity: normal CC: alan, bunk, clemens, funtasyspace, perex, tiwai
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.22.9 Subsystem:
Regression: No Bisected commit-id:

Description Jörg Hermsdorf 2007-10-27 03:44:12 UTC 
I cloned this bug, because the original one was nearly a year old and I have not the rights to reopen it.

+++ This bug was initially created as a clone of Bug #6709 +++

With several Logitech Webcam models there is a regular distortion (clicking noise) in the recorded audio. The kernel module that is used by those webcams is the "snd_usb_audio" audio module.

I'm running openSUSE 10.3 (x86_64) with kernel 2.6.22.9, the kernel is compiled with CONFIG_SND_DEBUG=y and as soon as I start recording audio, I see many of those messages in the dmesg output:

ALSA sound/usb/usbaudio.c:352: frame 0 active: -18

ALSA sound/usb/usbaudio.c:670: cannot submit urb (err = -45)

I have a suspicion what might be the reason for this clicking noise.
When I tried to grab video from my webcam with 'ffmpeg', 'ffmpeg' always aborted after a few seconds because it received incomplete/erroneous video frames. Laurant Pinchard, the developer of the uvcvideo driver explained it as following:
> The USB isochronous transfers are not error free. Packets can be lost, 
> which results in incomplete/erroneous frames.
> The driver currently handles complete and incomplete frames the same way. 
> I can add a driver option to make it drop incomplete frames, returning 
< complete frames only to the application.

Could it be, that the same happens with the audio frames sent by the webcam? I noticed that, when I try to record audio using 'sox' from '/dev/dsp2', 'sox' also aborts after recording for a few seconds (like 'ffmpeg' aborted after few seconds when an incomplete video frame was received). If I record from the webcam microphone via 'arecord', I have the same clicking noise in the recorded audio, but unlike 'sox', 'arecord' doesnt abort recording. 
Could it be, that those clicking sounds in the recorded audio are incomplete audio frames? So if the isochronous USB transfer is not perfect for the video data, it is self-evident that the same applies to the audio data transfer!?
Well, this is just the best assumption I currently have what could be the reason for the clicking noise. Maybe it helps to analyze this bug. 

Sample recordings of what the distortions sound like can be found here:
http://forums.quickcamteam.net/showthread.php?tid=6
Comment 1 Clemens Ladisch 2007-11-12 23:55:41 UTC 
The error code -18 means that the computer was not able to send data to the device when there was a packet scheduled to be sent. It is probable that some other module disabled interrupts for too long.

Please show all modules that are loaded (the output of "lsmod").
Comment 2 Jörg Hermsdorf 2007-11-13 08:29:10 UTC 
# lsmod
Module                  Size  Used by
usblp                  30976  0
nfsd                  271576  13
exportfs               22656  1 nfsd
uvcvideo               66692  1
compat_ioctl32         25472  1 uvcvideo
videodev               44416  2 uvcvideo
v4l1_compat            28676  2 uvcvideo,videodev
v4l2_common            36480  3 uvcvideo,compat_ioctl32,videodev
nls_iso8859_1          21888  0
nls_cp437              23680  0
vfat                   30336  0
fat                    70704  1 vfat
ipt_MASQUERADE         20480  1
xt_TCPMSS              21760  1
ppp_deflate            22912  0
zlib_deflate           36488  1 ppp_deflate
bsd_comp               22528  0
ppp_async              28800  0
crc_ccitt              18944  1 ppp_async
ppp_generic            45984  3 ppp_deflate,bsd_comp,ppp_async
slhc                   22784  1 ppp_generic
bnep                   50176  2
xt_tcpudp              20096  42
xt_pkttype             18688  6
ipt_LOG                23040  30
xt_limit               19840  30
snd_pcm_oss            67456  1
snd_mixer_oss          34176  1 snd_pcm_oss
snd_seq_midi           27136  0
snd_emu10k1_synth      25088  0
snd_emux_synth         54400  1 snd_emu10k1_synth
snd_seq_virmidi        24320  1 snd_emux_synth
snd_seq_midi_event     24576  2 snd_seq_midi,snd_seq_virmidi
snd_seq_midi_emul      23552  1 snd_emux_synth
snd_seq                74992  5 snd_seq_midi,snd_emux_synth,snd_seq_virmidi,snd_seq_midi_event,snd_seq_midi_emul
nfs                   266552  1
lockd                  84816  3 nfsd,nfs
nfs_acl                20352  2 nfsd,nfs
sunrpc                198600  13 nfsd,nfs,lockd,nfs_acl
af_packet              57100  2
ipt_REJECT             21504  3
xt_state               19328  23
iptable_mangle         19712  0
iptable_nat            24580  1
nf_nat                 37420  2 ipt_MASQUERADE,iptable_nat
iptable_filter         19840  1
nf_conntrack_ipv4      28816  25 iptable_nat
nf_conntrack           84188  5 ipt_MASQUERADE,xt_state,iptable_nat,nf_nat,nf_conntrack_ipv4
nfnetlink              23224  3 nf_nat,nf_conntrack_ipv4,nf_conntrack
ip_tables              37848  3 iptable_mangle,iptable_nat,iptable_filter
ip6_tables             31944  0
x_tables               37000  11 ipt_MASQUERADE,xt_TCPMSS,xt_tcpudp,xt_pkttype,ipt_LOG,xt_limit,ipt_REJECT,xt_state,iptable_nat,ip_tables,ip6_tables
cpufreq_conservative    24968  0
cpufreq_userspace      23680  0
cpufreq_powersave      18560  0
powernow_k8            31504  0
apparmor               58672  0
aes_x86_64             42280  1
cbc                    21376  1
blkcipher              23044  1 cbc
ohci_hcd               38020  0
dm_crypt               30480  1
xfs                   507560  2
loop                   36356  0
dm_mod                 77152  3 dm_crypt
rfcomm                 73896  5
l2cap                  57344  13 bnep,rfcomm
usbhid                 58160  0
hid                    43776  1 usbhid
ff_memless             22536  1 usbhid
snd_via82xx            47528  1
usb_storage           102816  0
snd_usb_audio         109952  1
snd_via82xx_modem      33420  0
k8temp                 22656  0
rtc_cmos               25016  0
i2c_viapro             26008  0
fglrx                1747484  0
i2c_core               43648  1 i2c_viapro
hwmon                  20232  1 k8temp
button                 26400  0
ide_core              165648  1 usb_storage
emu10k1_gp             20864  0
snd_emu10k1           159632  4 snd_emu10k1_synth
firmware_class         27520  1 snd_emu10k1
snd_ac97_codec        130248  3 snd_via82xx,snd_via82xx_modem,snd_emu10k1
ac97_bus               19328  1 snd_ac97_codec
rtc_core               38156  1 rtc_cmos
snd_pcm               108680  6 snd_pcm_oss,snd_via82xx,snd_usb_audio,snd_via82xx_modem,snd_emu10k1,snd_ac97_codec
rtc_lib                19968  1 rtc_core
gameport               32656  3 snd_via82xx,emu10k1_gp
ohci1394               51272  0
ieee1394              115800  1 ohci1394
skge                   58768  0
shpchp                 50716  0
snd_timer              42632  3 snd_seq,snd_emu10k1,snd_pcm
pci_hotplug            49396  1 shpchp
hci_usb                35100  2
floppy                 79624  0
snd_util_mem           22272  2 snd_emux_synth,snd_emu10k1
serio_raw              24068  0
snd_usb_lib            34688  1 snd_usb_audio
snd_hwdep              27528  3 snd_emux_synth,snd_usb_audio,snd_emu10k1
sr_mod                 33444  0
cdrom                  52392  1 sr_mod
snd_mpu401_uart        25984  1 snd_via82xx
snd_rawmidi            44544  5 snd_seq_midi,snd_seq_virmidi,snd_emu10k1,snd_usb_lib,snd_mpu401_uart
snd_seq_device         25620  6 snd_seq_midi,snd_emu10k1_synth,snd_emux_synth,snd_seq,snd_emu10k1,snd_rawmidi
snd                    84984  29 snd_pcm_oss,snd_mixer_oss,snd_seq_midi,snd_emu10k1_synth,snd_emux_synth,snd_seq_virmidi,snd_seq_midi_emul,snd_seq,snd_via82xx,snd_usb_audio,snd_via82xx_modem,snd_emu10k1,snd_ac97_codec,snd_pcm,snd_timer,snd_util_mem,snd_usb_lib,snd_hwdep,snd_mpu401_uart,snd_rawmidi,snd_seq_device
soundcore              25360  2 snd
snd_page_alloc         28048  4 snd_via82xx,snd_via82xx_modem,snd_emu10k1,snd_pcm
bluetooth              89092  8 bnep,rfcomm,l2cap,hci_usb
sg                     53304  0
ehci_hcd               50572  0
sd_mod                 45824  6
uhci_hcd               42144  0
usbcore               155816  11 usblp,uvcvideo,ohci_hcd,usbhid,usb_storage,snd_usb_audio,hci_usb,snd_usb_lib,ehci_hcd,uhci_hcd
edd                    26760  0
ext3                  156688  1
mbcache                26248  1 ext3
jbd                    89192  1 ext3
fan                    22792  0
pata_via               30212  4
sata_via               29700  0
libata                164224  2 pata_via,sata_via
scsi_mod              176536  5 usb_storage,sr_mod,sg,sd_mod,libata
thermal                34576  0
processor              59720  2 powernow_k8,thermal
Comment 3 Clemens Ladisch 2007-11-13 23:28:49 UTC 
Try without the fglrx module, or try to disable all 3D acceleration.
Comment 4 Jörg Hermsdorf 2007-11-19 02:37:38 UTC 
No, this didn't fix the problem. Fglrx can't be the problem, because I tested the webcam with 4 different systems and two of the have a Nvidia card. I experience the cracking noise on all 4 systems.
Comment 5 Jörg Hermsdorf 2007-11-21 02:02:05 UTC 
OK, it seems to be certain now, that those clicking noise is caused by a hardware bug of the SPCA525 chipset which is used by some Logitech webcams.

Martin Rubli from Logitech explained it in this thread: http://forums.quickcamteam.net/showthread.php?tid=6

> Here's some additional information on the older cameras for which the problem
> was initially reported. With some of the models based on the SPCA525 chipset 
> there is indeed a known issue that can cause clicks under certain 
> circumstances. Apparently it's something timing related, so it's hard to 
> predict when it occurs but Linux seems to trigger it much more often than 
> Windows.

> Therefore, on Windows there is a pop/click audio filter installed with some 
> camera models that fixes the problem before it reaches the applications. 
> That's why you can't hear it on Windows.

So the question is, would it be possible to implement a similar filter in the ALSA usb audio module, which is only activated for devices with a certain USB ID?
Comment 6 Clemens Ladisch 2007-11-21 03:29:52 UTC 
It would indeed be possible to implement such a filter, but the proper place to do this would be a userspace plugin that gets automatically activated by alsa-lib.

You only have to find someone to do this.