Ok,
so I've set a workaround in guvcview, it now uses the length filed if
bytesused is set to zero.
Anyway I think this violates the v4l2 api:
http://linuxtv.org/downloads/v4l-dvb-apis/buffer.html

bytesused - ..., Drivers must set this field when type refers to an
input stream, ...

without this value we have no way of knowing the exact frame size for
compressed formats.

And this was working in uvcvideo up until 3.16, I don't know how many
userspace apps rely on this value, but at least guvcview does, and
it's currently broken for uvcvideo devices in the latest kernels.

Regards,
Paulo

2014-09-30 9:50 GMT+01:00 Paulo Assis <pj.as...@gmail.com>:
> I referring to the following bug:
>
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1362358
>
> I've run some tests and after increasing verbosity for uvcvideo, I get:
> EOF on empty payload
>
> this seems consistent with the zero size frames returned by the driver.
> After VIDIOC_DQBUF | VIDIOC_QBUF, I get buf.bytesused=0
>
> Testing with an eye toy 2 (gspca), everything works fine, so this is
> definitly related to uvcvideo.
> This happens on all available formats (YUYV and MJPEG)
>
> Regards,
> Paulo
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