>There is a sample "ConvertMovieSoundTrack" which demonstrates how
to read audio from movies and
recompress it. If you want RAW, recompress it to NONE. You can
open pretty much any audio file
as a Movie, but I'm not sure which types allow access as per
ConvertMovieSoundTrack.
There are several reasons why MovieAudioExtraction is far superior to
this technique:
1) You get all the audio data from the movie, mixed together even if
it is spread across multiple tracks.
2) The example uses the SoundManager SoundConverter interface. This
will limit you to audio formats for which there is an sdec/scom, and
eliminates all high-res audio (eg, >2 channels, >65535 Hz). The
SoundManager is on its way out, and the CoreAudio AudioConverter,
using adec/aenc codec components, is the Wave Of The Present.
3) GetMediaSample() is not guaranteed to give you a useful packet of
data in all circumstances, particularly with some weirdo imported
formats that we've managed to finesse internally to play correctly.
MovieAudioExtraction will deliver any audio data that we're able to
successfully decode and play, in uncompressed format suitable for
signal processing, mixed to the output channel layout you're
interested in, so you don't even have to go down into CoreAudio
unless you want to use AudioUnits or do compression.
>Won't that limit his Application to Tiger and Panter/QT7 systems?
Well, QuickTime 7 systems, on all its current and future platforms.
But, as the saying goes: Time Marches On, and so does QuickTime.
Daniel Steinberg
QuickTime Engineering
>The audio files are most likely going to be compressed as m4a
and MP3, so I thought the easiest thing would be to let Quicktime
do the decompressing of the files and supply me with the raw data!?
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