Re: AAC options dialog 'Encoder Quality'
Re: AAC options dialog 'Encoder Quality'
- Subject: Re: AAC options dialog 'Encoder Quality'
- From: William Stewart <email@hidden>
- Date: Tue, 24 Apr 2007 12:43:24 -0700
The encoder quality property sets internal state in the AAC encoder
to make decisions between faster CPU execution or higher internal
resolution. This is a setting that is applied broadly across all many
CA features - the sample rate converter, the reverb and DLS Synth AU
all support this kind of trade off.
The internal implementation is left to the particular code involved,
and the gritty details of how the different settings are implemented
may (and do) change over time. For AAC a broad guideline you could
apply is:
Good
- emphasis on speed of execution, so some operations that may result
in loss of audio precision but are significantly faster will be taken.
Better
- primarily based on preserving audio precision required for 16 bit
sources. There is still some emphasis on faster operations, but not
where it is believe that the faster operation would compromise
typical 16 bit source material encoding quality
Best
- primarily based on preserving audio precision required for 24 bit
sources.
HTH
Bill
On 22/04/2007, at 5:08 PM, Andrea Barbieri wrote:
BF:=Brad Ford
BF> This question could be better answered on the CoreAudio list.
BF> Forwarding.
BF>
BF> -Brad Ford
BF> QuickTime Engineering
BF>
BF> Begin forwarded message:
BF>
BF> >From: Andrea Barbieri <email@hidden>
BF> >Date: April 20, 2007 6:26:59 AM PDT
BF> >To: email@hidden
BF> >Subject: AAC options dialog 'Encoder Quality'
BF> >
BF> >Hello,
BF> >
BF> >when using SoundConverter (I know I should be moving to the
newer API!) and
BF> >launching the options dialog (with title "MPEG-4 Audio
Compressor") for the
BF> >AAC component I wonder what changes when selecting the
different option
BF> >settings for Encoder Quality (Good, Better and Best).
BF> >
BF> >many thanks,
BF> >andrea
BF>
It is interesting that Technical Q&A QA1437:
http://developer.apple.com/qa/qa2006/qa1437.html
contains a reference to the Encoder Quality parameter, it is
flagged only
as an expert parameter (not invisible) but it does not show up in the
StdAudio dialog!
best regards,
andrea
--
Andrea Barbieri
Moving Image Research http://www.movingimageresearch.com/
The Workshop, Hampton Lane, Bristol, BS6 6LE, UK
Tel: +44 117 9732200 FAX: +44 117 9732210
PGP ID=0x034DFD5A
KeyFingerprint=C168EA9A7189538D214F1281A7529F32034DFD5A
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