I have a file coded in the Rhetorax ADPCM codec. I had downloaded the codec, but can only listen it on Windows Media Player. I am trying to convert it to mp3, but Audacity doesn’t recognize the file. It gives the following error message: “Audacity did not recognize the type of the file ‘xxxx.wav’. If it is uncompressed, try importing it using “Import RAW”.”
Have you installed the optional FFMPEG library? I don’t know if it can decode your file, but it can handle most formats.
I think Audacity should be able to use the same CODEC that WMP is using, but someone else will have to help/answer that.
RAW will NOT work, because it’s expecting “normal” linear PCM.
Correction - RAW MIGHT work. Try u-Law, A-Law, or VOX ADPCM. You may have to guess some of the other variables. But, I don’t think opening in RAW should be necessary… The file header should give Audacity (or WMP) the format, and WMP probably would not work with a headerless (RAW) file because it wouldn’t know the format either.
If you guess the wrong number of channels, you’ll get the wrong speed and maybe some distortion. The sample rate (kHz) also directly affects speed. 8kHz seems to be the most common with ADPCM, but I don’t know anything about Rhetorax.
If you get the byte order wrong, you could get just noise, but with 8-bit files you’ll just get the left & right channels mixed-up. These are probably 8-bit files, so it shouldn’t be a big deal.
The wrong offset can also cause pure noise with 16-bit files, and if there is a header you can get a short noise-glitch at the beginning of the file when the header gets converted to audio. An offset of 0 - 3 will most- likely work, although you might need a bigger offset to skip-over the header.
As far as I can see, Rhetorax ADPCM is not listed as a supported format for FFmpeg.
Perhaps the original device / software that created the file can convert it? Or perhaps the manufacturer of that device / software provides a format conversion tool?