Hardware H264 capture regression in UVC subsystem: wheezy(ok) => jessie(bad)

Hardware H264 capture regression in UVC subsystem: wheezy(ok) => jessie(bad)

[Peter Rabbitson]

Package: linux-image-3.16.0-4-amd64
Version: 3.16.7-ckt11-1
Tags: patch fixed-upstream

Greetings!

A little bit after the official Wheezy linux-image (3.2) a change to the 
UVC subsystem[1] was merged and subsequently released as linux 3.3. A 
long-unnoticed side effect of this patch was a regression that produced 
invalid timestamps on hardware-encoded H264 captures, which is known to 
affect at least 2 different devices: Logitech C920[2] and a builtin Acer 
Orbicam[3].

The problem was recently acknowledged by the UVC maintainer and a patch 
was produced which fixes the issue [4]. Afaik it is slated to be 
included during the Linux 4.3 merge window this month.

Since there is no way to work around this problem in userland [5], and 
there are many reports of this problem by different users [3], [6], [7], 
[8] it seems fitting to add this (rather small) patch[4] to debian's 
linux-image-3.16* quilt.

Thank you in advance!
Cheers

P.S. Adding a one-time CC to the linux-media mailing list, in case a 
part of the above is factually incorrect.

[1] 
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=66847ef
[2] http://sourceforge.net/p/linux-uvc/mailman/message/33164469/
[3] http://www.spinics.net/lists/linux-media/msg92089.html
[4] http://www.spinics.net/lists/linux-media/msg92022.html
[5] http://ffmpeg.org/pipermail/ffmpeg-user/2015-July/027630.html
[6] https://trac.ffmpeg.org/ticket/3956
[7] http://sourceforge.net/p/linux-uvc/mailman/message/33564420/
[8] 
http://askubuntu.com/questions/456175/logitech-c920-webcam-on-ubuntu-14-04-hesitates-chops-every-3-seconds