[TriEmbed] BBB /dev/video0 issues

[Alex Davis]

Bill,

I've seen USB issues capturing purely still images and from running
whatever 'motion' does (max_framerate set to '5' or less).

I was hoping it was some sort of v4l2 lib issue on 3.8 but I've seen it
on 3.14 as well. I can live with something higher than 3.14 as I am not
using the GPIO and don't care if overlays work or not.

What I was trying to do, briefly, was run motion and have it drop stills
to an NFS export where they could be viewed via a web browser. Does the
BBB hang the ethernet off the USB like the Pi? Maybe there's a bandwidth
issue? Hard to believe that, since the jpeg files are only about 60 KB.

When I get some more free time, I'll run this with the files saved only
to the SD card and wrap it in strace.


On Wed, Jul 8, 2015, at 01:00 PM, triembed-request at triembed.org wrote:
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> Today's Topics:
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>    1. Re: BBB USB webcam issues? (Bill Farrow)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 8 Jul 2015 08:27:20 -0400
> From: Bill Farrow <bill at arrowsreach.com>
> To: TriEmbed <triembed at triembed.org>
> Subject: Re: [TriEmbed] BBB USB webcam issues?
> Message-ID:
> 	<CAPm8Nr3QvZNuqh5ntaTw9LubHxcp4qs26Yau=o3aXCE=2ExVVA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> I suspect that it is not a power issue, but a bandwidth or CPU
> throughput limitation.
> 
> Note that the Logitech C920 webcam is able to stream h.254 video over
> USB, which means the data rate is lower than other video encodings and
> the BBB CPU does not have to do any video compression.
> 
> Can you capture still images at higher resolutions ?
> 
> What are you doing with the video stream on the BBB ? Are you
> processing it, streaming it over the network, writing to flash ? Each
> one of these will have different resource limitations and potential
> bottlenecks.
> 
> Bill
> 
> On Tue, Jul 7, 2015 at 10:40 PM, Carl Nobile via TriEmbed
> <triembed at triembed.org> wrote:
> > Alex,
> >
> > Both the BBB and RPi have version 2 USB which specifies 500mA as the maximum
> > allowed current through a USB connector. The max speed of a USB 2 is 480
> > megabits per second. Here is an interesting addressing some of the issue you
> > mentioned.
> > http://electronics.stackexchange.com/questions/24700/why-are-usb-devices-slower-than-480-mbit-s
> >
> > Carl
> >
> >
> > On Mon, Jul 6, 2015 at 2:51 PM, Alex Davis via TriEmbed
> > <triembed at triembed.org> wrote:
> >>
> >> Anyone have experience with the BeagleBone Black and USB webcams? In my
> >> experience with v4l2 and UVC USB webcams on the BBB, getting an image
> >> above 320x240 is unreliable and 320x240 or below is occasionally
> >> unreliable. I've seen this on two separate BBBs under 3.8 and 3.14
> >> kernels. It is more reliable if you set the webcam to send a compressed
> >> image stream (JPEG) vs uncompressed (YUV), so it makes me think the
> >> issue is data-rate dependent on the USB bus.
> >>
> >> I am using a Microsoft Lifecam Cinema camera. It is rock-solid on my
> >> Debian laptop running a 3.8 kernel at up to the native 12800x720
> >> resolution.
> >>
> >> I know with the early Raspberry Pi there is an issue with limited USB
> >> current, but I don't think that's the case with the BBB. I use at
> >> minimum a 2A 5V supply, which should be plenty for the BBB and the USB
> >> webcam. Could it be some hardware issue limited to the original 2 GB
> >> eMMC models that I have?
> >>
> >> There isn't much on the web with regards to BBB-specific webcam issues.
> >> I've seen BBB projects using high-end logitech cameras for live
> >> streaming, so it must work for some.
> >>
> >> --
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> >
> >
> >
> > --
> > -------------------------------------------------------------------------------
> > Carl J. Nobile (Software Engineer)
> > carl.nobile at gmail.com
> > -------------------------------------------------------------------------------
> >
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-- 
"The theater of noise is proof of our potential."
|\ |  (¯  \/ |¯\  |V| |\ ¯|¯ |¯) | \/ | | | |¯\ (¯   /¯  /\ |V|
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You won't find me on Facebook.