[PD-dev] call for discussion: native video for Pd

chris clepper cgc at humboldtblvd.com
Sun Jun 4 21:22:32 CEST 2006


On 6/4/06, Mathieu Bouchard <matju at artengine.ca> wrote:
>
> On Sun, 4 Jun 2006, chris clepper wrote:
>
> > Can you go into more detail about the revisions to block~?  My rough
> > calculations put a 720x480 YCbCr image at about 64 times the data of a
> > single 96khz audio signal.  RGBA is double that.
>
> How do you compute that?
>
> DV-NTSC is 720 px * 480 px * 30 Hz * 2 samples/px^2 = 20736000 samples/s
> DV-PAL  is 720 px * 576 px * 25 Hz * 2 samples/px^2 = 20736000 samples/s
> 96 kHz mono is            96000 Hz * 1 samples      =    96000 samples/s
>
> and 20736000/96000 = exactly 216 = 6*6*6 but closest powers of 2 are 2^7 =
> 128 and 2^8 = 256. (comparing with stereo sound doesn't change the
> relative closeness of powers of two)


I forgot to make the video signal 4 bytes per channel in my calculation.  If
you compare the 4 byte audio to single byte per channel video then it is 54
times the data.  64 is the next power of two.

Your numbers are the right ones to use.
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