Re: How to encode with AAC High Efficiency?
Re: How to encode with AAC High Efficiency?
- Subject: Re: How to encode with AAC High Efficiency?
- From: Eric Allamanche <email@hidden>
- Date: Mon, 31 Mar 2008 10:35:32 -0700
Jens,
the high efficiency AAC codec is not implemented in the AudioCodecs
library, though the 'aach' 4 char code is in a header file. It's there
to help third party developers to use consistent naming conventions
(same as for 'ac-3' etc).
Eric
On Mar 30, 2008, at 1:24 PM, Jens Alfke wrote:
I can't figure out how to use ExtAudioFile to output AAC
HighEfficiency (aka AAC+). I'm using the ConvertAudio sample code to
test with. If I use the command-line flags "-d aach -f
m4af" (corresponding to the constant kAudioFormatMPEG4AAC_HE) the
program throws an exception and aborts. If instead I use 'aac ' or
'aacl', it works fine.
The error comes from this call in utils.cpp:
err = AudioFormatGetProperty(kAudioFormatProperty_FormatInfo, 0,
NULL, &size, &outputFormat);
If outputFormat.mFormatID has been set to kAudioFormatMPEG4AAC_HE,
this function returns the error 'fmt?'.
I've searched apple.com for AAC "high efficiency" but didn't find
anything useful, only some messages from a few years ago indicating
that QuickTime didn't support it. But that was before Leopard, and
of course QT != CA.
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