Allow to play/draw one channel specified by parameter

[whenov]

No description provided.

[katspaugh]

if (channel > -1) {
    this.splitter.connect(this.merger, channel);
} else {
    for (var c = 0; c < channels; c++) {
        this.splitter.connect(this.merger, c);
    }
}

[whenov]

I tried to omit the third parameter also, but the output of splitter is only connected to the first channel of the merger (tested on newest Chrome/Firefox).

Although the last two parameters are marked as optional in the document of AudioNode.connect, the default behaviour is not described.

[katspaugh]

Nice! Does it add much overhead in terms of performance, though?

[coveralls]

Coverage decreased (-0.2%) to 4.756% when pulling 47a4217 on whenov:channel into 3e7b67e on katspaugh:master.

[whenov]

@katspaugh Although I haven't tested its performance (and I haven't considered how to do it), the added logic seems not to include costly overhead.

But I'm not sure about the splitter/merger nodes, whose performance are dependent on browser implementations. If this channel-switch function is not required by most users, we can directly connect analyser to gainNode when channel === -1, which however decreases a little readability.

[katspaugh]

Could you measure CPU load/memory usage with and without your changes? You can simply open the default OS activity monitor and watch the browser process.

[whenov]

@katspaugh Good idea, will do it tomorrow.

[whenov]

@katspaugh I tested its performance using Chrome's profiling tool, the increased execution time is negligible.

[katspaugh]

Cool, merged! Thanks!