From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752910AbbAMCIP (ORCPT ); Mon, 12 Jan 2015 21:08:15 -0500 Received: from lists.s-osg.org ([54.187.51.154]:47805 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752089AbbAMCIO (ORCPT ); Mon, 12 Jan 2015 21:08:14 -0500 Message-ID: <54B47E0C.50500@osg.samsung.com> Date: Mon, 12 Jan 2015 19:08:12 -0700 From: Shuah Khan Organization: Samsung Open Source Group User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Hans Verkuil , m.chehab@samsung.com, hans.verkuil@cisco.com, dheitmueller@kernellabs.com, prabhakar.csengg@gmail.com, sakari.ailus@linux.intel.com, laurent.pinchart@ideasonboard.com, ttmesterr@gmail.com CC: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] media: au0828 remove video and vbi buffer timeout work-around References: <7210fb24807adf46f76197a12dab11358f4dcd30.1418918402.git.shuahkh@osg.samsung.com> <54B3D5D5.9060602@xs4all.nl> In-Reply-To: <54B3D5D5.9060602@xs4all.nl> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/12/2015 07:10 AM, Hans Verkuil wrote: > On 12/18/2014 05:20 PM, Shuah Khan wrote: >> au0828 does video and vbi buffer timeout handling to prevent >> applications such as tvtime from hanging by ensuring that the >> video frames continue to be delivered even when the ITU-656 >> input isn't receiving any data. This work-around is complex >> as it introduces set and clear tier code paths in start/stop >> streaming, and close interfaces. After the vb2 conversion, the >> timeout handling is introducing instability as well as feeding >> too many blank green screens, resulting in degraded video quality. > > Why would this result in degraded video quality? And which instability > exactly? What I noticed was that I was seeing a few too many green screens and I had to re-tune xawtv when the timeout code is in place. My thinking was that this timeout handling could be introducing blank green frames when there is no need. However, I can't reproduce the problem on 3.19-rc4 base which is what I am using to test the changes to the patch series. Hence, I am not positive if the timeout code indeed was doing anything bad. > >> Without this timeout handling, both xawtv, and tvtime are working >> well with good quality video. I am seeing tvtime hangs. > > Erm, tvtime without the recent 'tvtime: don't block indefinitely waiting > for frames' patch will not work well with au0828 without the timeout code > if there is no valid video data. > > This should at minimum be mentioned in the commit log. I will resend the patch with the updated commit log knowing full well that it might not be accepted. I do have to re-cut the patch after the changes to address your comments on the vb2 conversion patch. It applies, with fuzz, so I decided to re-cut the patch. thanks, -- Shuah -- Shuah Khan Sr. Linux Kernel Developer Open Source Innovation Group Samsung Research America (Silicon Valley) shuahkh@osg.samsung.com | (970) 217-8978