On 03/24/17 13:21, Jose Abreu wrote: > 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". That sounds good. Sorry for adding to your workload, but there is no point to have a flag that in practice is meaningless. I'm actually very curious about the results! Regards, Hans > > 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 >> >
