[Webkit-unassigned] [Bug 34452] Initial patch for audio engine: AudioBus and helper classes

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=34452





--- Comment #5 from Chris Rogers <crogers at google.com>  2010-02-01 20:38:52 PST ---
Hi Simon, thanks for having a look.  If you think about it in CoreAudio terms,
the AudioChannel is very similar to the "AudioBuffer" type in CoreAudio.  The
AudioBus is similar to "AudioBufferList".  But, of course, since these are C++
classes they are somewhat easier to work with than the CoreAudio versions. 
Please note that these data types are used internally in the engine
implementation and are not expected to be exposed through the javascript API,
so I don't think we'll confuse our javascript developers with the naming
conventions.  For audio software engineers, a "bus" is a very common term in
audio engineering and is used to denote a grouping of "channels".  In schematic
diagrams for audio devices they are often shown as a line with a small diagonal
slash. From my perspective as an audio engineer, these terms are not at all
surprising and I think they make a lot of sense.

In the current engine code and any code I can envision for the future there
will be no place for interleaved audio.  Non-interleaved (planar) Float32 PCM
(nominal -1 -> +1) will be the canonical format.  The file-loading code I have
written already takes care of the details of getting interleaved file data
loaded into the right format.  All of the AudioUnits I wrote at Apple conformed
to this format.

The AudioChannel and AudioBus classes have served very well as building blocks
for the engine so far, and I'm very confident they will be sufficient to
support future engine improvements like the modular routing we talked about.

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