Recording to AAC format, basic questions
Recording to AAC format, basic questions
- Subject: Recording to AAC format, basic questions
- From: Nir Soffer <email@hidden>
- Date: Sat, 8 Jul 2006 04:02:44 +0300
I need to record sound from some input device, typically built-in
microphone or other microphone to AAC or QuickTime movie format. The
recording are 60-90 minutes long (people talking), and should create
small files (the recordings are served over the web later). The file
format should be mono, 22KHz, 16Kbs bitrate. I need to support only
Tiger.
After searching and reading the docs and lot of example code, it
seems that the easiest way is to use MTCoreAudio to get the data from
the default input device, and feed the data into ExtAudioFile using
ExtAudioFileWriteAsync.
How can I produce mono from stereo input I get fron built in Audio?
Does a simple microphone give true stereo output or its actually the
same data duplicated, so I can just use one channel?
I see that the built in sound provides only 32/44/48KHz - how can I
get 22KHz? can I down-sample using the AudioConverter owned by the
ExtAudioFile?
I don't have any idea what sample rate will provide some other device
in the field, e.g. wireless microphone, what is the general strategy
to handle this?
When the user change the default device during a recording, I have to
stop the recording and reconfigure using the new default device, or
there is a way to use the current selected default device in a
transparent way?
What about changing the data source, for example, selecting line in
instead of digital in - can you continue to record from built-in
audio after the data source was changed?
Best Regards,
Nir Soffer
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