[TriEmbed] BBB USB webcam issues?

[Bill Farrow]

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.
>>
>> --
>> "The theater of noise is proof of our potential."
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>
>
>
> --
> -------------------------------------------------------------------------------
> Carl J. Nobile (Software Engineer)
> carl.nobile at gmail.com
> -------------------------------------------------------------------------------
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