Some Notes on Indeo Audio (samples needed BTW)

I’ve been working on this codec for a while and somewhat got it working.

Good news — it employs the same algorithms as its predecessor, except that it has stereo mode.

Bad news — it feeds slightly different values to those algorithms. So some tables used in calculations and number of free bits in the block (for allocation) differ. I’ve almost got it and hacked version of our IMC decoder outputs almost perfect sound. My suspicions are that it modifies original IMC tables for stereo mode case (since it codes audio in mid-side stereo mode it makes sense).

The problem is that there’s only one sample with this codec and it’s extremely short. So if someone has more files with Indeo Audio please provide them to us.

3 Responses to “Some Notes on Indeo Audio (samples needed BTW)”

  1. ami_stuff says:

    I was not able to create IAC2 samples, but it looks like IMC with 11khz and 44khz modes doesn’t decode correctly because of “read coefficients failed”:

    btw. mpc8 decoder seems to fail with files created with –quality higher
    than 6 (“maxband 32 too large”):

  2. Kostya says:


    For encoding IAC driver needs an additional iacenc.dll, one can easily find it in Internet by name.

    And thanks for bugreporting, though it should be more convenient with 😉 I’ll try to fix MPC, no promises on IMC though.

  3. compn says:

    awesome work! 🙂
    do you like working more on audio or video codecs ?

    the uncommon audio codecs list (from picsearch) has some indeo audio codec samples:

    i mirrored the indeo audio samples from that list to ffmpeg sample repo: