Convert to AIFC with ima4 compression

Question

A lot of audio programs, such as Audacity, support encoding files as AIFF (Audio Interchange File Format, developed by Apple Inc.).

However, I need specifically an AIFF file that has been compressed with ima4, making it an AIFC file.

The internet seems to be nearly clueless about AIFC and ima4. "convert to AIFC" (with quotes) yields exactly 0 results on Google (3M for MP3, 90K for WAV, 45K for FLAC, ...).

Possible solutions:

• ffmpeg. I know ffmpeg -i wavefile.wav -f aiff wavefile.aiff converts to AIFF but I can't figure out how to specify the compression algorithm.
• afconvert. According to here, we can use afconvert -f AIFC -d ima4 [file]. But this is a Mac-only program and I only have access to Windows and Linux Mint machines.
• afftools. See here. This strangely seems to be a Fedora-only program, and I once again can't find anything on it on Google (if it even does what I want).
• Adobe Audition. See here. Once again I do not own this paid-for software.

Answer 1

I thought I'd take a crack at an ffmpeg solution since it's always proved itself to be infinitely versatile for me.

A cursory search of the ffmpeg docs found no useful references to ima4. However, I then realised that ima4 refers to the ADPCM IMA QuickTime codec. Back to the ffmpeg docs, and this appears on the list of supported audio codecs.

Now we know what ffmpeg thinks the codec is called, but not how to refer to it. Running ffmpeg -encoders produces a list of all codecs for which encoding is supported, along with their identifiers. In our case, we can see:

$ ffmpeg -encoders | grep "ADPCM IMA QuickTime"
 A..... adpcm_ima_qt         ADPCM IMA QuickTime

Great! Now we know to tell ffmpeg to use the adpcm_ima_qt codec. Which is as simple as:

$ ffmpeg -i file.wav -c:a adpcm_ima_qt file.aiff
Input #0, wav, from 'file.wav':
  Duration: 00:00:54.31, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> adpcm_ima_qt (native))
Press [q] to stop, [?] for help
Output #0, aiff, to 'file.aiff':
  Metadata:
    encoder         : Lavf58.12.100
    Stream #0:0: Audio: adpcm_ima_qt (ima4 / 0x34616D69), 44100 Hz, stereo, s16p, 352 kb/s
    Metadata:
      encoder         : Lavc58.18.100 adpcm_ima_qt
size=    2485kB time=00:00:54.31 bitrate= 374.9kbits/s speed= 306x
video:0kB audio:2485kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.002829%

The -c:a option is the same as specifying -acodec; both of these specify the codec to encode audio streams with.

And finally a quick inspection with ffprobe (note ima4 on line 3):

$ ffprobe file.aiff
Input #0, aiff, from 'file.aiff':
  Duration: 00:00:54.31, start: 0.000000, bitrate: 374 kb/s
    Stream #0:0: Audio: adpcm_ima_qt (ima4 / 0x34616D69), 44100 Hz, 2 channels, s16p, 352 kb/s