Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965372AbdCXMWX (ORCPT ); Fri, 24 Mar 2017 08:22:23 -0400 Received: from us01smtprelay-2.synopsys.com ([198.182.60.111]:41893 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965067AbdCXMVu (ORCPT ); Fri, 24 Mar 2017 08:21:50 -0400 Subject: Re: [PATCH 0/3] Handling of reduced FPS in V4L2 To: Hans Verkuil , Jose Abreu , References: <1939bd77-a74d-3ad6-06db-2b1eaa205aca@synopsys.com> <3a7b5c81-834c-8d1e-2181-6d8f57d20f7b@cisco.com> CC: Carlos Palminha , Mauro Carvalho Chehab , Hans Verkuil , From: Jose Abreu Message-ID: Date: Fri, 24 Mar 2017 12:21:39 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.107.19.88] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2777 Lines: 69 Hi Hans, On 24-03-2017 12:12, Hans Verkuil wrote: > On 03/24/17 12:52, Jose Abreu wrote: >> Hi Hans, >> >> >>>> Can you please review this series, when possible? And if you >>>> could test it on cobalt it would be great :) >>> Hopefully next week. >> Thanks :) >> >>> Did you have some real-world numbers w.r.t. measured >>> pixelclock frequencies and 60 vs 59.94 Hz and 24 vs 23.976 Hz? >> I did make some measurements but I'm afraid I didn't yet test >> with many sources (I mostly tested with signal generators which >> should have a higher precision clock than real sources). I have a >> bunch of players here, I will test them as soon as I can. >> Regarding precision: for our controller is theoretically and >> effectively enough: The worst case is for 640x480, and even in >> that case the difference between 60Hz and 59.94Hz is > 1 unit of >> the measuring register. This still doesn't solve the problem of >> having a bad source with a bad clock, but I don't know if we can >> do much more about that. > I would really like to see a table with different sources sending > these different framerates and the value that your HW detects. > > If there is an obvious and clear difference, then this feature makes > sense. If it is all over the place, then I need to think about this > some more. > > To be honest, I expect that you will see 'an obvious and clear' > difference, but that is no more than a gut feeling at the moment and > I would like to see some proper test results. Ok, I will make a table. The test procedure will be like this: - Measure pixel clock value using certified HDMI analyzer - Measure pixel clock using our controller - Compare the values obtained from analyzer, controller and the values that the source is telling to send (the value displayed in source menu for example [though, some of them may not discriminate the exact frame rate, thats why analyzer should be used also]). Seems ok? I will need some time, something like a week because my setup was "borrowed". Best regards, Jose Miguel Abreu > >>> I do want to see that, since this patch series only makes sense if you can >>> actually make use of it to reliably detect the difference. >>> >>> I will try to test that myself with cobalt, but almost certainly I won't >>> be able to tell the difference; if memory serves it can't detect the freq >>> with high enough precision. >> Ok, thanks, this would be great because I didn't test the series >> exactly "as is" because I'm using 4.10. I did look at vivid >> driver but it already handles reduced frame rate, so it kind of >> does what it is proposed in this series. If this helper is >> integrated in the v4l2 core then I can send the patch to vivid. > That would be nice to have in vivid. > > Regards, > > Hans >