Freq (coupl/high) and ac3

[nimrodim]

Freq (coupl/high) what does this really mean?
Searching the internet i found this:
Freq (coupl/high) - [kHz], coupling frequency and high freuency. In ac3 some channels (in most cases all channels) are grouped in one coupling channel beginning from some frequency - coupling frequency and stored in the bitstream in that form. So channels are really independent only in some frequency band - up to coupling frequency. High frequency is a maximum frequency coded, so it defines total frequency bandwidth.

Now i had an audio sample i converted to ac3 stereo with 3 different encoders:
ffmpeg: 0,20.906
Intervideo ac3 encoder: 0,18.093
softencode: 18.093,20.343

now do you think this has any effect on quality?

Nim
:)

[Sycho]

The channel coupling is used to save space, and it is done very well i might add. It is just like joint stereo, but the ac3 decoder can (usually) decouple extremely well

Now i had an audio sample i converted to ac3 stereo with 3 different encoders:
ffmpeg: 0,20.906
Intervideo ac3 encoder: 0,18.093
softencode: 18.093,20.343
as to the maximum frequency coded, well just choose a higher bitrate and it will go up, choose an even higher one, for stereo, and you wil see no channel coupling, like Linkin Park's DVD-Audio, DD 2.0 448kbps STEREO!

[nimrodim]

First thanks,
Second all of these reuslts were using the same bitrate...so according to what you said ffmpeg: 0,20.906 is the best result - no coupling and higher bitrate?

Nim

[Sycho]

the ffmpeg would be the worst result because it does not use channel coupling, think of it this way, with channel coupling you can have hight quality because it is combining common sounds in the high end, so more bits can goto the low end and mid. without channel coupling the same amount of bit are being used, but, now they are evenly split for each channel, it turn a lower quality.