Play ADPCM stream on iOS (MS IMA 0x11)

Question

I'm using the AudioUnit / RemoteIO API to achieve playback of streaming audio. Other formats such as a-law and u-law are working fine.

Here is an example of how I am setting up the a-law format:

    audioFormat.mSampleRate       = format->nSamplesPerSec;
    audioFormat.mFormatID         = kAudioFormatALaw;
    audioFormat.mFormatFlags      = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioFormat.mFramesPerPacket  = 1;
    audioFormat.mChannelsPerFrame = format->nChannels;
    audioFormat.mBitsPerChannel   = format->wBitsPerSample;
    audioFormat.mBytesPerFrame    = (format->wBitsPerSample * format->nChannels) / 8;
    audioFormat.mBytesPerPacket   = audioFormat.mBytesPerFrame * audioFormat.mFramesPerPacket;

The format I am trying to work with is MS ADPCM, described here.

From what I understand, in this case I need to somehow calculate the number of frames per packet. The only additional information I have is the nBlockAlign field, which multimedia wiki describes as "the size of a block of IMA-encoded data".

I'm at a loss with this.

How is the frames per packet calculated? Does it involve the block size from nBlockAlign?

I see kAudioFormatDVIIntelIMA and kAudioFormatAppleIMA4 listed as formats. Does iOS even support this kind of ADPCM?