Re: Interpolation on WaveShaperNode?

On Mon, May 13, 2013 at 3:27 PM, Ehsan Akhgari <ehsan.akhgari@gmail.com>wrote:

> On Mon, May 13, 2013 at 3:09 PM, Chris Rogers <crogers@google.com> wrote:
>
>>
>>
>>
>> On Mon, May 13, 2013 at 11:32 AM, Ehsan Akhgari <ehsan.akhgari@gmail.com>wrote:
>>
>>> FWIW, in Gecko, I'm implementing linear interpolation by default.
>>>
>>
>> Good, I think that's what we should do for the default, but we could
>> consider an attribute "linear" or "nearest-neighbor" to select the
>> interpolation method.  On the other hand, it's pretty easy to create the
>> "bit-crushing" effects even with linear interpolation as long as the table
>> size is suitably large, so maybe all we need is linear.
>>
>> WebKit/Blink are not doing the linear interpolation, so that'll have to
>> change.
>>
>
> Sounds good.  Can you please spec this as well?
>
>
>> By the way, I've been looking in some detail about how to implement a
>> "high-quality" mode for the shaper, which up-samples the signal to a higher
>> sample-rate (2x, in the simple case), does the shaping, then down-samples
>> back down to the node sample-rate.  This type of processing is important
>> for guitar amp simulation and other simulation of analog gear to avoid the
>> harsh aliasing.  I think the default mode of operation for the shaper
>> should not do this up-sampling, but that it would be good to opt-in by
>> having a .quality attribute.
>>
>
> Are you planning to add the quality attribute right now, or wait for a
> "post-v1" spec?
>

I think it's important to get in as soon as possible, because developers
are already trying to use the WaveShaperNode for more serious pro-level
purposes and are bumping up against the quality issues:
http://dashersw.github.io/pedalboard.js/demo/

I actually wrote a pretty good first pass at the up-down-sampling code
yesterday, and was able to test it at a basic level.  This is low-level
"blitter" code which I'm happy to share with Mozilla.

Chris


>
> --
> Ehsan
> <http://ehsanakhgari.org/>
>