AAC encoder - what codec or converter setting to encode to Mono?
AAC encoder - what codec or converter setting to encode to Mono?
- Subject: AAC encoder - what codec or converter setting to encode to Mono?
- From: "Simon Liu" <email@hidden>
- Date: Wed, 12 Jul 2006 00:17:04 +0100
OS X 10.4. 7 - I can encode Linear PCM to AAC using
AudioConverterFillComplexBuffer(), but I have been unable to set the
converter/codec settings to encode from LPCM Stereo to AAC Mono
(ideally downmixed).
My three attempts so far:
1. Changed the converter's destination ASBD mChannelsPerFrame per
frame to 1 does not work, as the converter does not init and returns
'?tmf'
2. I found the audio converter property
kAudioCodecPropertyOutputChannelLayout, but it is not writable.
3. I tried settingthe property kAudioConverterChannelMap with a channel map of:
SInt32 channelMap[1] = { 0 };
I thought the converter would encode using audio from the first
channel, and ignore the second input channel. In fact, nothing
happened, and the resulting M4A was in stereo.
When I get the converter properties, I also see the following:
key = "Channel Configuration";
"limited values" = (Stereo);
So it seems the converters' other settings may be preventing me from
choosing Mono as the channel configuration.
Can anybody help? Thank you.
Regards,
Simon
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