From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25130 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758395Ab0FCIkV (ORCPT ); Thu, 3 Jun 2010 04:40:21 -0400 Message-ID: <4C076AD5.2090909@redhat.com> Date: Thu, 03 Jun 2010 10:41:57 +0200 From: Hans de Goede MIME-Version: 1.0 To: =?UTF-8?B?QmrDuHJuIE1vcms=?= CC: linux-media@vger.kernel.org Subject: Re: [Bugme-new] [Bug 16077] New: Drop is video frame rate in kernel .34 References: <20100602140916.759d7159.akpm@linux-foundation.org> <4C072451.7090001@infradead.org> <87r5kod2dm.fsf@nemi.mork.no> In-Reply-To: <87r5kod2dm.fsf@nemi.mork.no> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi, On 06/03/2010 09:03 AM, Bjørn Mork wrote: > Mauro Carvalho Chehab writes: >> Em 02-06-2010 18:09, Andrew Morton escreveu: >>> On Sun, 30 May 2010 14:29:55 GMT >>> bugzilla-daemon@bugzilla.kernel.org wrote: >>> >>>> https://bugzilla.kernel.org/show_bug.cgi?id=16077 >>> >>> 2.6.33 -> 2.6.34 performance regression in dvb webcam frame rates. >> >> I don't think this is a regression. Probably, the new code is allowing a higher >> resolution. As the maximum bandwidth from the sensor to the USB bridge doesn't >> change, and a change from QVGA to VGA implies on 4x more pixels per frame, as >> consequence, the number of frames per second will likely reduce by a factor of 4x. >> >> I've asked the reporter to confirm what resolutions he is setting on 2.6.33 >> and on 2.6.34, just to double check if my thesis is correct. > > Well, the two video clips attached to the bug shows the same resolution > but a much, much lower video (and overall) bitrate in 2.6.34. Output > from mediainfo: > I notice in the original bug report that you claim that the lower framerate clip with 2.6.34 has "much better quality", could you define this a bit better. I think that what is happening is the code for the new (correct) sensor is setting a higher exposure value (and thus a lighter / less dark image), but setting a higher exposure value comes at the cost of framerate. As the framerate can never be higher then 1 / exposure_time_for_1_frame. 2 things: 1) Go the preferences in cheese, and see which resolutions you can select, and make sure you are using the same resolution in 2.6.34 and 2.6.33 2) Start a v4l2 control panel applet, like v4l2ucp or gtk-v4l, and try playing around with the controls (note the controls inside cheese are software not hardware controls so don't use those). Regards, Hans