Re: uvcvideo: Trying to lower the URB buffers on eMPIA minicam

[Pierre ANTOINE <nunux@free.fr>]

Laurent,

I finally did it !

On usbcore, I correct the bandwidth of endpoint 4 from 912 to 1024.

maxp = usb_endpoint_maxp(&endpoint->desc) & 0x07ff;
if (maxp == 912) endpoint->desc.wMaxPacketSize = cpu_to_le16(1024);

On uvcvideo:
I set: 768 B/frame bandwidth
I use endpoint alt-setting 4 by disabling some checking code.
And I get uvcvideo: Allocated 5 URB buffers of 32x1024 bytes each.

So I can run the 4 cam on the same USB card:

gst-launch v4l2src device=/dev/video0 !
'video/x-raw-yuv,width=160,height=120,framerate=30/1' ! xvimagesink
gst-launch v4l2src device=/dev/video1 !
'video/x-raw-yuv,width=160,height=120,framerate=30/1' ! xvimagesink
gst-launch v4l2src device=/dev/video2 !
'video/x-raw-yuv,width=160,height=120,framerate=30/1' ! xvimagesink
gst-launch v4l2src device=/dev/video3 !
'video/x-raw-yuv,width=160,height=120,framerate=30/1' ! xvimagesink

I will try to do it less dirty next week ...

Thank's a lot for pointing me on usbcore ...

Many regards,

Pierre

Selon Laurent Pinchart <laurent.pinchart@ideasonboard.com>:

> lsusb parses the raw descriptors. Could you print the wMaxPacketSize value
> for all the endpoints in the uvcvideo driver ? The value is also exported
through
> a sysfs attribute.
>
> --
> Regards,
>
> Laurent Pinchart
>
>