Audacity Forum

IMA ADPCM vs MS ADPCM

I have some wav files that were recorded at a high bitrate and i want to re-export them with a lower bitrate. They are mostly voice-wavs and i don't need any high quality or anything.

I did some quick reading on what i should do, and i experimented by exporting to 8bit and 4bit wav types... but my question is... what should i be saving these wavs as?

WAV (microsoft 4bit IMA ADPCM) or
WAV (microsoft 4bit MS ADPCM) ???

Just curious. What are your suggestions? I read descriptions of the two types but being a novice it didn't clear my mind up much on the differences between the two.

For the smallest file size for speech the best format is "speex"
http://www.speex.org/

Hmm. Looks promising. I'm on a windows machine though and didn't find any current windows binaries for downloading... just a beta and an older version that's not recommended. Am i just overlooking something?

The supplier of download materials has apparently failed. Many of the program distributions went off line.

I have no more information than that.

Koz

The Speex encoder/decoder bundle is available here http://www.rarewares.org/others.php
There is also a drag and drop front end for it on the same page.

(the same site also hosts my favourite MP3 encoder "LameDropXPd")

Very kewl. I will download and experiment with that....

But keeping in topic with my original post.... IMA vs MS .... can someone elaborate on which is best to use or what the pros/cons are in layman's terms?

AFAIK the format is identical. ADPCM was invented by Bell Laboratories in about 1969. I'm guessing that MS-ADPCM is Microsoft's implementation of ADPCM. It is an outdated codec and not a lot to say about it other than it is fast. There are much better codecs around now.