Webcam Driver Bug while using two Multilaser Cameras simultaneously

Webcam Driver Bug while using two Multilaser Cameras simultaneously

[Daniel Moraes]

I'm using Ubuntu 10.04 and I need to get images from two Multilaser
Cameras simultaneously. First I tried to do that using OpenCV, but I
got an error. So, I entered the OpenCV Mailing List to report that and
I discovered that's a driver problem. To ensure that, I used mplayer
to get imagens from the both cameras and I got the following error
(again):

> v4l2: ioctl streamon failed: No space left on device

The cameras model is Multilaser WC0440.

This problem only happens when I try to capture images from two
IDENTICAL cameras simultaneously. I have three cameras here, two
Multilaser Cameras and one HP Camera, from my laptop. I have no
problem to capture images from my HP Camera and one of the Multilaser
Cameras simultaneously, but when I try to capture from the both
Multilaser Cameras simultaneously, i got that error.

I think that the problem may be something related to the generic
driver. When I use the Multilaser Cameras, they use the same driver.
That's not happen with the HP Camera, which uses another driver.
Someone knows a solution for that?

Att,
 Daniel Bastos Moraes
 Graduando em Ciência da Computação - Universidade Tiradentes
 +55 79 88455531

Re: Webcam Driver Bug while using two Multilaser Cameras simultaneously

[Mauro Carvalho Chehab]

Hi Daniel,

Em 21-09-2010 16:05, Daniel Moraes escreveu:
> I'm using Ubuntu 10.04 and I need to get images from two Multilaser
> Cameras simultaneously. First I tried to do that using OpenCV, but I
> got an error. So, I entered the OpenCV Mailing List to report that and
> I discovered that's a driver problem. To ensure that, I used mplayer
> to get imagens from the both cameras and I got the following error
> (again):
> 
>> v4l2: ioctl streamon failed: No space left on device

This is not a driver issue, but a limit imposed by USB specs. This
error code is returned by USB core when you try to use more than 100% of
the available bandwidth for an USB isoc stream.

The amount of bandwidth basically depends on what type of compression
is provided by your webcams.

You'll need to plug the other webcam on a separate USB bus.
> 
> The cameras model is Multilaser WC0440.
> 
> This problem only happens when I try to capture images from two
> IDENTICAL cameras simultaneously. I have three cameras here, two
> Multilaser Cameras and one HP Camera, from my laptop. I have no
> problem to capture images from my HP Camera and one of the Multilaser
> Cameras simultaneously, but when I try to capture from the both
> Multilaser Cameras simultaneously, i got that error.
> 
> I think that the problem may be something related to the generic
> driver. When I use the Multilaser Cameras, they use the same driver.
> That's not happen with the HP Camera, which uses another driver.

Probably, the HP Camera is connected internally into a different USB bus,
or provide a more compressed stream.

> Someone knows a solution for that?
> 
> Att,
>  Daniel Bastos Moraes
>  Graduando em Ciência da Computação - Universidade Tiradentes
>  +55 79 88455531
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Webcam Driver Bug while using two Multilaser Cameras simultaneously

[Mauro Carvalho Chehab]

Em 23-09-2010 23:19, Daniel Moraes escreveu:
> Hi Mauro,
> 
> thanks a lot for your help. I would only take a few more questions.
> 
>    1. A computer can have more than one USB Bus? As far as I know the USB Bus is unique.

Yes, it can have as many bus as designed by the manufacturer. You can also add other buses
by buying USB adapter cards.

>    2. Whereas HP webcam uses the same USB Bus but has a more compressed stream, is there a way to compress or reduce the stream of a webcam that uses a generic driver like the HP Webcam does with your drive?

It will depend on the chipset used by the cameras, the screen resolution, and the number of frames per sec.

>    3. Is there a way to check the amount of bandwich in an USB Bus?

Yes. you can watch /proc/bus/usb/devices. It will provide not only the information about each connected
device on your usb bus, but also the speed used.

For example, a quick test here:

$ lsusb
Bus 008 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 007 Device 003: ID 2040:4200 Hauppauge 
Bus 007 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

This machine has 2 USB 2.0 buses (bus 7 and bus 8), with an WinTV USB2 device
connected at bus 7, reading a stream at 640x480x30fps:

cat /proc/bus/usb/devices showed (I removed the info for the USB 1.1 buses):

T:  Bus=08 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 2.06
S:  Manufacturer=Linux 2.6.35+ ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1d.7
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=07 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
B:  Alloc=408/800 us (51%), #Int=  0, #Iso=  5
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 2.06
S:  Manufacturer=Linux 2.6.35+ ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1a.7
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=07 Lev=01 Prnt=01 Port=05 Cnt=01 Dev#=  3 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=2040 ProdID=4200 Rev= 1.00
S:  Product=WinTV USB2
S:  SerialNumber=0002819348
C:* #Ifs= 3 Cfg#= 1 Atr=80 MxPwr=500mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=   0 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 1 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=1024 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 2 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=1448 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 3 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=2048 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 4 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=2304 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 0 Alt= 5 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=2580 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 6 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=2892 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 0 Alt= 7 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
E:  Ad=82(I) Atr=01(Isoc) MxPS=3072 Ivl=125us
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 1 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio
I:* If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
I:  If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=83(I) Atr=01(Isoc) MxPS=  20 Ivl=125us


The bandwidth is per bus. In this case, bus 7 shows:
	B:  Alloc=408/800 us (51%), #Int=  0, #Iso=  5

Eg: the stream is using 51% of the USB for just one single stream. If I want to plug another
device, I'll need to use bus 8, as it is free:
	B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0

If I try to use bus 7 for another HVR-950 using the same resolution, it will return 
the error you got (-ENOSPC), as otherwise, it would be using more than 800 slots, of an
USB bus that can provide only 800 ISOC slots, according with USB 2.0 specs.


Cheers,
Mauro
> 
> Att,
>  Daniel Bastos Moraes
> 
> 
> 
> On Tue, Sep 21, 2010 at 4:48 PM, Mauro Carvalho Chehab <mchehab@redhat.com <mailto:mchehab@redhat.com>> wrote:
> 
>     Hi Daniel,
> 
>     Em 21-09-2010 16:05, Daniel Moraes escreveu:
>     > I'm using Ubuntu 10.04 and I need to get images from two Multilaser
>     > Cameras simultaneously. First I tried to do that using OpenCV, but I
>     > got an error. So, I entered the OpenCV Mailing List to report that and
>     > I discovered that's a driver problem. To ensure that, I used mplayer
>     > to get imagens from the both cameras and I got the following error
>     > (again):
>     >
>     >> v4l2: ioctl streamon failed: No space left on device
> 
>     This is not a driver issue, but a limit imposed by USB specs. This
>     error code is returned by USB core when you try to use more than 100% of
>     the available bandwidth for an USB isoc stream.
> 
>     The amount of bandwidth basically depends on what type of compression
>     is provided by your webcams.
> 
>     You'll need to plug the other webcam on a separate USB bus.
>     >
>     > The cameras model is Multilaser WC0440.
>     >
>     > This problem only happens when I try to capture images from two
>     > IDENTICAL cameras simultaneously. I have three cameras here, two
>     > Multilaser Cameras and one HP Camera, from my laptop. I have no
>     > problem to capture images from my HP Camera and one of the Multilaser
>     > Cameras simultaneously, but when I try to capture from the both
>     > Multilaser Cameras simultaneously, i got that error.
>     >
>     > I think that the problem may be something related to the generic
>     > driver. When I use the Multilaser Cameras, they use the same driver.
>     > That's not happen with the HP Camera, which uses another driver.
> 
>     Probably, the HP Camera is connected internally into a different USB bus,
>     or provide a more compressed stream.
> 
>     > Someone knows a solution for that?
>     >
>     > Att,
>     >  Daniel Bastos Moraes
>     >  Graduando em Ciência da Computação - Universidade Tiradentes
>     >  +55 79 88455531
>     > --
>     > To unsubscribe from this list: send the line "unsubscribe linux-media" in
>     > the body of a message to majordomo@vger.kernel.org <mailto:majordomo@vger.kernel.org>
>     > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 

Re: Webcam Driver Bug while using two Multilaser Cameras simultaneously

[Daniel Moraes]

Mauro,

first of all I would like to thank you. By using the commands that you
told me, I was able to find the problem. Now I need to find a
solution.

Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 005: ID 04fc:2001 Sunplus Technology Co., Ltd
Bus 003 Device 004: ID 04fc:2001 Sunplus Technology Co., Ltd
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 002: ID 04f2:b015 Chicony Electronics Co., Ltd VGA
24fps UVC Webcam
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

As I showed above, I have 4 USB buses here (two usb 2.0 and two usb
1.1). However, all three external USB ports from my notebook seem to
use the same USB bus (Bus 003) and the HP Webcam the Bus 002.

When I turn one of the Multilaser cameras on, in one port, the Bus 003
stream uses 80% of the limit. When I turn the another camera on, in a
different port, it doesn't work because it uses the same USB bus.

Is there a way to change the USB bus from any of my external usb ports?

Att,
 Daniel Bastos Moraes
 Graduando em Ciência da Computação - Universidade Tiradentes
 +55 79 88455531


On Fri, Sep 24, 2010 at 10:35 AM, Mauro Carvalho Chehab
<mchehab@redhat.com> wrote:
>
> Em 23-09-2010 23:19, Daniel Moraes escreveu:
> > Hi Mauro,
> >
> > thanks a lot for your help. I would only take a few more questions.
> >
> >    1. A computer can have more than one USB Bus? As far as I know the USB Bus is unique.
>
> Yes, it can have as many bus as designed by the manufacturer. You can also add other buses
> by buying USB adapter cards.
>
> >    2. Whereas HP webcam uses the same USB Bus but has a more compressed stream, is there a way to compress or reduce the stream of a webcam that uses a generic driver like the HP Webcam does with your drive?
>
> It will depend on the chipset used by the cameras, the screen resolution, and the number of frames per sec.
>
> >    3. Is there a way to check the amount of bandwich in an USB Bus?
>
> Yes. you can watch /proc/bus/usb/devices. It will provide not only the information about each connected
> device on your usb bus, but also the speed used.
>
> For example, a quick test here:
>
> $ lsusb
> Bus 008 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 007 Device 003: ID 2040:4200 Hauppauge
> Bus 007 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
>
> This machine has 2 USB 2.0 buses (bus 7 and bus 8), with an WinTV USB2 device
> connected at bus 7, reading a stream at 640x480x30fps:
>
> cat /proc/bus/usb/devices showed (I removed the info for the USB 1.1 buses):
>
> T:  Bus=08 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
> B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
> D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
> P:  Vendor=1d6b ProdID=0002 Rev= 2.06
> S:  Manufacturer=Linux 2.6.35+ ehci_hcd
> S:  Product=EHCI Host Controller
> S:  SerialNumber=0000:00:1d.7
> C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
> I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
> E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms
>
> T:  Bus=07 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
> B:  Alloc=408/800 us (51%), #Int=  0, #Iso=  5
> D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
> P:  Vendor=1d6b ProdID=0002 Rev= 2.06
> S:  Manufacturer=Linux 2.6.35+ ehci_hcd
> S:  Product=EHCI Host Controller
> S:  SerialNumber=0000:00:1a.7
> C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
> I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
> E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms
>
> T:  Bus=07 Lev=01 Prnt=01 Port=05 Cnt=01 Dev#=  3 Spd=480 MxCh= 0
> D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
> P:  Vendor=2040 ProdID=4200 Rev= 1.00
> S:  Product=WinTV USB2
> S:  SerialNumber=0002819348
> C:* #Ifs= 3 Cfg#= 1 Atr=80 MxPwr=500mA
> I:  If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=   0 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 1 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=1024 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 2 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=1448 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 3 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=2048 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 4 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=2304 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:* If#= 0 Alt= 5 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=2580 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 6 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=2892 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:  If#= 0 Alt= 7 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=em28xx
> E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=128ms
> E:  Ad=82(I) Atr=01(Isoc) MxPS=3072 Ivl=125us
> E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
> I:* If#= 1 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio
> I:* If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
> I:  If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
> E:  Ad=83(I) Atr=01(Isoc) MxPS=  20 Ivl=125us
>
>
> The bandwidth is per bus. In this case, bus 7 shows:
>        B:  Alloc=408/800 us (51%), #Int=  0, #Iso=  5
>
> Eg: the stream is using 51% of the USB for just one single stream. If I want to plug another
> device, I'll need to use bus 8, as it is free:
>        B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
>
> If I try to use bus 7 for another HVR-950 using the same resolution, it will return
> the error you got (-ENOSPC), as otherwise, it would be using more than 800 slots, of an
> USB bus that can provide only 800 ISOC slots, according with USB 2.0 specs.
>
>
> Cheers,
> Mauro
> >
> > Att,
> >  Daniel Bastos Moraes
> >
> >
> >
> > On Tue, Sep 21, 2010 at 4:48 PM, Mauro Carvalho Chehab <mchehab@redhat.com <mailto:mchehab@redhat.com>> wrote:
> >
> >     Hi Daniel,
> >
> >     Em 21-09-2010 16:05, Daniel Moraes escreveu:
> >     > I'm using Ubuntu 10.04 and I need to get images from two Multilaser
> >     > Cameras simultaneously. First I tried to do that using OpenCV, but I
> >     > got an error. So, I entered the OpenCV Mailing List to report that and
> >     > I discovered that's a driver problem. To ensure that, I used mplayer
> >     > to get imagens from the both cameras and I got the following error
> >     > (again):
> >     >
> >     >> v4l2: ioctl streamon failed: No space left on device
> >
> >     This is not a driver issue, but a limit imposed by USB specs. This
> >     error code is returned by USB core when you try to use more than 100% of
> >     the available bandwidth for an USB isoc stream.
> >
> >     The amount of bandwidth basically depends on what type of compression
> >     is provided by your webcams.
> >
> >     You'll need to plug the other webcam on a separate USB bus.
> >     >
> >     > The cameras model is Multilaser WC0440.
> >     >
> >     > This problem only happens when I try to capture images from two
> >     > IDENTICAL cameras simultaneously. I have three cameras here, two
> >     > Multilaser Cameras and one HP Camera, from my laptop. I have no
> >     > problem to capture images from my HP Camera and one of the Multilaser
> >     > Cameras simultaneously, but when I try to capture from the both
> >     > Multilaser Cameras simultaneously, i got that error.
> >     >
> >     > I think that the problem may be something related to the generic
> >     > driver. When I use the Multilaser Cameras, they use the same driver.
> >     > That's not happen with the HP Camera, which uses another driver.
> >
> >     Probably, the HP Camera is connected internally into a different USB bus,
> >     or provide a more compressed stream.
> >
> >     > Someone knows a solution for that?
> >     >
> >     > Att,
> >     >  Daniel Bastos Moraes
> >     >  Graduando em Ciência da Computação - Universidade Tiradentes
> >     >  +55 79 88455531
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>

Re: Webcam Driver Bug while using two Multilaser Cameras simultaneously

[Mauro Carvalho Chehab]

Em 26-09-2010 21:29, Daniel Moraes escreveu:
> Mauro,
> 
> first of all I would like to thank you. By using the commands that you
> told me, I was able to find the problem. Now I need to find a
> solution.
> 
> Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 003 Device 005: ID 04fc:2001 Sunplus Technology Co., Ltd
> Bus 003 Device 004: ID 04fc:2001 Sunplus Technology Co., Ltd
> Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 002 Device 002: ID 04f2:b015 Chicony Electronics Co., Ltd VGA
> 24fps UVC Webcam
> Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> 
> As I showed above, I have 4 USB buses here (two usb 2.0 and two usb
> 1.1). However, all three external USB ports from my notebook seem to
> use the same USB bus (Bus 003) and the HP Webcam the Bus 002.
> 
> When I turn one of the Multilaser cameras on, in one port, the Bus 003
> stream uses 80% of the limit. When I turn the another camera on, in a
> different port, it doesn't work because it uses the same USB bus.
> 
> Is there a way to change the USB bus from any of my external usb ports?

In general, you can't. They're hardwired. You'll need to buy an extra 
USB adapter. There are a few PCMCIA ones, like:

http://www.byterunner.com/byterunner/category=PCMCIA+USB+and+Firewire+Cards
http://shopping.uol.com.br/pcmcia-usb.html?nortrk=1&url=/index.html&lout=47,49&psid=1#rmcl

There are also some models for Express Card bus. Just be sure to buy one
that will work with your notebook (if you're in doubt, you may see 
http://en.wikipedia.org/wiki/ExpressCard).

> 
> Att,
>  Daniel Bastos Moraes
>  Graduando em Ciência da Computação - Universidade Tiradentes
>  +55 79 88455531