Re: rounding issue with RTCRtpEncodingParameters scales?

I still don’t think I fully understand exactly what those values need to be set to in order to setup the correct ratios. For the sake of clarity, if the base layer is scaled resolution of 30%, and you had 3 geometric spatial layers, what exactly would be the value of the encoding parameters for each layer?

-- 
Robin Raymond

On July 18, 2014 at 3:09:57 PM, Peter Thatcher (pthatcher@google.com) wrote:

I think we can until we run into real implementation issues.  I have a feeling it won't be a big deal.


On Thu, Jul 17, 2014 at 12:37 PM, Robin Raymond <robin@hookflash.com> wrote:

dictionary RTCRtpEncodingParameters {
    //...
    double              resolutionScale;
    double              framerateScale;
}

These are floats with relative values. The trouble is that there are fixed geometric relations. It must be 1.0, 0.5, 0.25, 0.125, etc for resolution scaling…

Maybe this isn’t an issue but I’m a bit concerned that float rounding issues might cause us problems.

For example, if you start at a base scale of 0.3 (i.e. resolution is 0.3 of source), are the layerings relative to 0.3, i.e. (1/1 * 0.3), (1/2 * 0.3), (1/4 * 0.3) ?

or would the scale be like this:
0.3, 1/1, 1/2, 1/4, 1/8, etc?

Also if people use dividers vs fixed value like: 1/8 vs 0.125, could we end up in situations where the values almost match but don’t quite due to float rounding problems?


Just a concern…

Robin