On Sat, Sep 05, 2015 at 06:46:04AM -0700, Doug Anderson wrote: > Russell, > > On Sat, Sep 5, 2015 at 1:31 AM, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxxx> wrote: > > On Fri, Sep 04, 2015 at 07:03:11PM -0700, Doug Anderson wrote: > >> AKA: just replace your entire "compute_n" function with: > >> > >> return (128 * freq) / 1000; > >> > >> ...and it's 100% simpler _and_ gets you a (marginally) better rate > >> (assuming you really have 22.175000). If it was just about a > >> 32000.222 vs 32000 I'd not be saying anything right now. It's about > >> adding complexity. > > > > No. It doesn't work for all cases. Do the calculations for every > > sample rate in those tables in the HDMI spec, and you'll find out > > why. > > If you know the answer, just tell me. If you're talking about 74.25 > vs. 32 kHz it is further evidence of what I'm saying. Note that > picking only one of the two listed CTS values again puts you in a > worse position for regenerating the proper audio clock then just using > the default N=4096. No it doesn't. 74.25MHz/1.001 * 4096 / (128 * 32000) = 74175 (rounded down) Now do the calcuation. (74.25MHz/1.001) / 74175 * 4096 = 4096045.511 => 32000.35556Hz => error of 0.001111% Now for the calcuation using the proscribed figures. (74.25MHz/1.001) / 210937 * 11648 = 4096009.709 => 32000.07585Hz => error of 0.000237% That's significantly less error using that than your "better" idea. Now, if we take the pixel clock rate as 74.175MHz, which is just a representation of 74.25MHz/1.001: 74.175MHz / 210937 * 11648 = 4095964.198 => 31999.72029Hz => error of 0.0008741% That's still lower than your "better" idea. And as I've already said, the pixel clock rate given to us here will be the _specified_ clock rate of 74.175MHz, *not* some cocked up platform screwed crap that you think we will. It _will_ be 74175 not 74170 or some other shite like that. Right, I've had enough. I'm going to be ignoring this thread from now on, this is a waste of my time - you clearly have no understanding of what's going on here. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
