Re: [dev-servo] println!("Hello from NCSU");

Josh Bowman-Matthews Sat, 23 Mar 2019 19:28:24 -0700

Yes, all of that sounds sensible to me.

Cheers,
Josh


On 3/23/19 2:12 PM, Akhilesh Venkatasubramanian wrote:

Hi Josh,

Thank you for the reply. It clarifies a lot of doubts.

1. Just checking if we have got the entire idea for the first task right:

So what we have to do is uncomment the line 277 in param.rs
<https://github.com/servo/media/blob/1c4a8917a2c44bf9901dcf41919ec567967a36de/audio/src/param.rs#L277>
and
then add a new enum variant to AutomationEvent and write the processing
algorithm as defined here
<https://webaudio.github.io/web-audio-api/#dom-audioparam-setvaluecurveattime>
for
SetValueCurveAtTime and implement it similar to the RampValueAtTime
<https://github.com/servo/media/blob/1c4a8917a2c44bf9901dcf41919ec567967a36de/audio/src/param.rs#L384-L405>
  implementation?

2. For the 2nd part which is the example, I came across the
constant_source.rs
<https://github.com/servo/media/blob/029475e1412d97c6350016d9a9db7c1f1203b523/examples/constant_source.rs>
file
that uses the RampValueAtTime
<https://github.com/servo/media/blob/1c4a8917a2c44bf9901dcf41919ec567967a36de/audio/src/param.rs#L384-L405>,
so can I write a similar example to check the output of the
SetValueCurveAtTime function that we will be adding to param.rs? I'm
assuming we will also be expecting an audio output.

Thanks for your patience and helping us out,
Akhilesh


On Fri, Mar 22, 2019 at 10:52 PM Josh Bowman-Matthews <j...@joshmatthews.net>
wrote:

On 3/22/19 5:58 PM, Balaji Janakarajan Hari wrote:

Hi Josh

1. We are trying to implement the functionality and have a few q's. The
setValueCurveAtTime
<

http://definitelytyped.org/docs/webaudioapi--waa/interfaces/audioparam.html#setvaluecurveattime


talks
about Automation event, which I assume that the term
*UserAutomationEvent *refers
to in the issue <https://github.com/servo/media/issues/204> but could

you

please help us understand what *UserAutomationEvent exactly* does and

where

the *setValueCurveAtTime *fn would be called?


The names I refer to in the issue are types that can be found in the
actual codebase:

https://github.com/servo/media/blob/9d9f557fc7bfa78075b83edd822557548c9d4344/audio/src/param.rs#L259-L280


https://github.com/web-platform-tests/wpt/blob/master/webaudio/the-audio-api/the-audioparam-interface/audioparam-setValueCurveAtTime.html
is an example of test code that uses setValueCurveAtTime.

https://developer.mozilla.org/en-US/docs/Web/API/AudioParam/setValueCurveAtTime
contains an example of working code that uses the API.

2. Is there a similar implementation done previously that we could use as
reference as well?


The existing automation events like SetValueAtTime and RampToValueAtTime
could be useful references.

3. It does refer
<

https://webaudio.github.io/web-audio-api/#dom-audioparam-setvaluecurveattime

that
I would need to call *setValueAtTime *and I assume this is implemented
<

https://github.com/servo/media/search?q=setValueAtTime&unscoped_q=setValueAtTime


as I see here and can you also let us know where the  *setValueAtTime*

is

defined?


If I understand the question, I believe you are looking for
https://github.com/servo/servo/issues/22897 which defines the DOM API
that websites can make use of.

4. The fn does two commands as per the teams understanding,
During the time interval, it sets array of values
After the time, startTime+duration, a constant value would be set until
another automationEvent starts.

So could you please help us in figuring out where would this value be
passed and where/how the fn knows that another automationEvent would

start?

The processing for automation events happens in this code:

https://github.com/servo/media/blob/9d9f557fc7bfa78075b83edd822557548c9d4344/audio/src/param.rs#L357-L416

The code that decides which event to process lives here:

https://github.com/servo/media/blob/9d9f557fc7bfa78075b83edd822557548c9d4344/audio/src/param.rs#L113-L166

Does that help?

Cheers,
Josh
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Re: [dev-servo] println!("Hello from NCSU");

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