OpenWrt Forum Archive

Topic: Problems Using two webcam simultaneously

The content of this topic has been archived on 12 Apr 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

I'm following this tutorial http://h-wrt.com/en/doc/webcam, however when using two webcam simultaneously openwrt gives me an error "no space left",'ve seen something about saying regarding the memory of openwrt, but it is not true, because a desktop pc gives the same message, so I believe it is something with relation to configuration.

Probably, the problem must be the fate of Engraving believe that by default is at the following address / tmp, already tried to change but do not know if I did right or if it has to be done something else.

Anyone ever managed to put 2 or more Webcams at the same time in openwrt?
thank you

I've got 2 USB webcams and a DSLR attached to a TL-MR3020. Works like a charm.

which model of webcams that you are using? You also followed the same tutorial, or have another you used?
thanks

1x Logitech Sphere AF
1x Logitech C910

Main difference: I'm using the webcams as still-picture webcams with fswebcam, not for streaming with mjpeg-streamer.

I'll try streaming 2 webcams with mjpeg-streamer this evening.

By the way: "Probably, the problem must be the fate of Engraving believe that by default is at the following address / tmp, already tried to change but do not know if I did right or if it has to be done something else."

Can you express this in proper english? I don't understand what you want to say with this sentence...

Checked it out now for 45mins:

mjpg_streamer -i "input_uvc.so -d /dev/video0 -r 800x600 -f 1" -o "output_http.so -p 8090 -w /www/webcam0/"
mjpg_streamer -i "input_uvc.so -d /dev/video1 -r 800x600 -f 1" -o "output_http.so -p 8091 -w /www/webcam1/"

works perfect.

You need to give more info:

- Which webcams are you using
- what version of OpenWRT
- what version of mjpeg_streamer
- which router hardware are you using
- everything else.

(Last edited by tmo26 on 20 Jun 2013, 00:11)

Regarding the error
"I get a "No space left on device" (-28) error when trying to stream from more than one camera simultaneously."

please see also http://www.ideasonboard.org/uvc/faq/ -> scroll down to the bottom of the page to find answers to this problem

Interestingly, I am using the Logitech C170 camera with a TL MR3020 and one webcam works great, but when I added a second C170 through a powered USB hub, the second C170 would not work at all using MJPG. I got the ""No space left on device (-28) " error as well. Each C170 connected individually would work fine. I then tried one C170 with a Pro 9000 and success! Both worked fine. I also tried one C170 with a Microsoft Lifecam, and that worked as well. Evidently there is something preventing two C170's working together at once. So anyone having issues with connecting two webcams of the same model number may want to try mixing the models and see if they get a better outcome.

(Last edited by hasso on 12 Sep 2013, 07:41)

Just checked out:
- DIR-505 (64MB RAM) + trunk r38002
- LogiLink 4p active/self powered hub (I wouldn't try this with a passive/bus powered one smile
- mjpg_streamer
- 3 webcams (2x Logitech P9000 + 1x C270) simultaneously
- 800x600 each stream

root@DIR-505-3:~# free
             total         used         free       shared      buffers
Mem:         61420        35996        25424            0         1524
-/+ buffers:              34472        26948
Swap:            0            0            0

Mem: 35852K used, 25568K free, 0K shrd, 1524K buff, 11620K cached
CPU:  12% usr   6% sys   0% nic  78% idle   0% io   0% irq   1% sirq
Load average: 0.04 0.10 0.13 1/49 18618 

Working perfectly for 30min now.

I'll try 2x C270 tomorrow.

Tested today with the above setup:
2x C270; 640x480 @ 1 / 2 / 5fps -> OK
2x C270; 800x600 @ 1fps -> NOK, no space left on device

lsusb -v delivers for Pro9000 + C270 the same values:

        wWidth                            640
        wHeight                           480
        dwMinBitRate                 24576000
        dwMaxBitRate                147456000
        dwMaxVideoFrameBufferSize      614400


        wWidth                            800
        wHeight                           600
        dwMinBitRate                 38400000
        dwMaxBitRate                230400000
        dwMaxVideoFrameBufferSize      960000

While having the same bandwidth requirements in theory, the BW requested in reality seems to differ for both cams:
- C270 always requests the max. BW (230,4mbit@800x600), thus 2x C270 isn't possible
- Pro 9000 requests less than that, otherwise 2x P9000 + C270 would not be possible imho.

Seems to be the same issue as with the Microsoft LifeCam Cinema + Studio
---> http://www.ideasonboard.org/uvc/#footnote-13

hasso wrote:

So anyone having issues with connecting two webcams of the same model number may want to try mixing the models and see if they get a better outcome.

This issue is not restricted to same make / same model.
Just take 2 webcams that *always* request the dwMaxBitRate.
If the sum of the requested bitrate is bigger than 80% of 480mbit (=384mbit), then at least one cam will not work and tell you, that there's no space left on the device.

See also:

"No space left on device" ---> http://www.ideasonboard.org/uvc/faq/#faq7
Cam requesting always max bandwidth ---> http://www.ideasonboard.org/uvc/#footnote-13

Ah, well, the C270 is listed there with just a checkmark... no comment on the bandwidth requirements as for the MS Lifecam Cinema + Studio... so you can't completely rely on this list. But it seems to be a good start.

The discussion might have continued from here.