[M4IF Technotes] Looking for HE AAC test software / AAC-LC

[Hans-Juergen Bardenhagen]

On Friday, 20.06.03, 17:44 (received 21.06.03, 06:11) Dave Singer wrote:
>> And could you tell us which version
>> of the AAC codec is implemented in iTunes 4.01 and with which
>> quality setting compared to QuickTime 6.3?

> I believe that QT and iTunes use a common encoder, but I'm afraid the
> details of the settings that iTunes uses are unknown to me.

In the meantime I've seen two interesting quotes from Mr. Stanley Kuo,  
your AAC developer, the first addressing the question mentioned above  
<http://www.hydrogenaudio.org/index.php?act=ST&f=2&t=10457&st=100&>:
"iTunes does use the SAME encoder as QT, and iTunes does give the user  
the ability to change the encoder's mode. iTunes uses the "Better"  
quality mode (not the fastest) which is optimized to perform best with  
16bit source material (ie. CD source). "Best" quality mode is targetted  
at 24bit source material (eg. DVD source) and there should be NO  
discernible difference in quality for CD source between these two modes  
of the encoder. Generally it's just a waste of CPU to use best quality  
for 16 bit source, but there's no harm done by doing this of course."
The second quote is taken from the results of the 128 kbps listening  
tests and answers the question if QuickTime 6.x uses a CBR or a VBR  
codec <http://rarewares.hydrogenaudio.org/test/aac128test/results.html>:
"a CBR codec does not only allocate the necessary bits according to the  
masking thresholds (as a VBR does) but also pay attention to meet the  
bit reservoir limit in order to maintain a constant output bit flow. In  
order to faithfully respect the target bitrate, QT AAC even encodes  
silence with the desired bitrate, e.g. 128 kbps/stereo."
Now where did I read that passage before... ;-)
ZZee ya, Hans-Jürgen