I have looking for an explanation of when to use TNS and MS for encoding AAC LC files.

First off I don't quite understand what Temporal Noise Shaping (TNS) and M/S joint channel coding (MS) are, let alone when they should or should not be used for encoding AAC LC files.

Could someone help me out here? I plan to write a FAQ about AAC LC for newbies but I can't find a good explanation of both of these and when to use or not use each one (or both together).

I see that some encoding programs have both of these options turned off by default and other have them turned on by default, which is best for general 128k AAC LC encoding of stereo 44.1kHz files?

Info: http://www.audiocoding.com/wiki

If your encoder works correctly you should always have TNS and MS turned on (encoder will dynamically switch and find correct usage).

Menno

Thanks Menno for the link. I appreciate it and will check it out. Site appears unreachable to me currently though.

It's Sourceforge. Please be parient

Correct me if I am wrong, but from the old days of mp3 encoding, I distinctly remember never using MS or JS (mid-side or joint stereo) for a high-quality encode at high bitrates, eg 256 kbps+. Doesn't using those options use more cpu time to decode too?

So, what is your concern ? Speed or quality ?
Anyhow, I don't think that using (adaptive) MS Stereo is that a big performance hit in comparison to ("normal") stereo (though I haven't checked). But adaptive MS Stereo has always the power (on every bitrate) to increase quality because it can exploit inter-channel redundancies.

I'm sure that there's some kind of joint-stereo FAQ around here explaining all details.

bye,
Sebastian