--- On Fri, 7/2/10, Laurent Pinchart <[email protected]> wrote:
> What models have you tried ?
>
#1: An OEMed camera from PixArt (093a:2801), similar to PAC7332.
#2: Retail Logitech Webcam C600 (046d:0808)
> I've attached a new patch to this e-mail that fixes the
> problem mentioned
> above. Could you please add a printk statement in
> uvc_queue_next_buffer when
> buf->error is set, to check that every occurrence of the
> "USB isochronous
> frame lost" message results in the frame being dropped in
> uvc_queue_next_buffer ?
>
I applied the updated patch and added the printk. In MJPG mode, the driver
does drop each frame after printing "USB isochronous frame lost". However,
the isoc frame drops are very rare. I also tried the Logitech camera in
YUYV mode, and it has much more frequent isoc frame drops, but not always
a corresponding video frame drop. I suspect this is because buf is NULL in
uvc_video_decode_isoc.
> It's also quite possible that, due to a buffer underrun,
> part of the image
> gets dropped by the camera. Could you try a YUYV UVC
> device, and see if you
> get any frame dropped by the buffer length test despite no
> USB isochronous
> frame loss being detected ?
>
I tried this with the Logitech camera in YUYV mode. I added a printk when
buf.length != buf.bytesused in uvc_video_deocode_isoc, and it did trigger
a few times. This printk was always preceded by "USB isochronous frame
lost", so it seems like the condition is properly detected.
> Regards,
>
> Laurent Pinchart
>
For reference, in my testing I use the Logitech camera mentioned above and
set it to 176x144, 15 fps, which it supports with either MJPG or YUYV. My
test application can create MJPG AVIs which are consistently corrupted, but
the YUYV AVIs appear fine. The MJPG corruption appears without any
"dropped" messages occurring.
Regards,
Filter
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