Converting Audio to AC-3 using afconvert

audiocommand linefile conversion

I'm trying to use afconvert to convert an audio file to AC-3 format. It's 5.1 audio, having already been converted from DTS to WAV (using ffmpeg, since afconvert doesn't seem to deal with DTS).

As you can see, I've tried various parameter incantations, including trying to use a different container formats, but with no success:

$ afconvert -f ac-3 test.wav 
Error: ExtAudioFileCreateWithURL failed ('typ?')
$ afconvert -f ac-3 -d ac-3 test.wav 
Error: ExtAudioFileCreateWithURL failed ('typ?')
$ afconvert -f caff -d AC-3 test.wav 
Error: ExtAudioFileSetProperty ('cfmt') failed ('fmt?')

I have been able to encode it to an AAC file successfully, so it's presumably something with the AC-3 encoding, but Googling those errors yields no results. Does anyone know how to properly convert to AC-3 with afconvert?

If you want to do some testing yourself, I found some free 5.1 DTS sample files here. Note that while the file extension is .wav, they're actually DTS files, not WAV. To replicate my desired workflow, decode to a WAV file with ffmpeg: ffmpeg -i input.wav -acodec pcm_s16le -f wav output.wav, then you'll have a proper 5.1 WAV file afconvert should be able to work with.

Best Answer

Can't you use ffmpeg? This seemed to work for the DTS WAV files here:

ffmpeg -i test.wav -ab 640k test.ac3

Related Solutions

Automator – Converting WAV Files to MP3 Using LAME

Automator 'hangs' when attempting to use LAME encoder unfortunately. It's also not efficient or advisable to try and use a multi-threaded process as an Automator Service. For tasks such as this it's best to either run a simple script or use an alternate method.

The script below will encode a 20Mb .wav to .mp3 in 3 seconds! (at the highest quality settings)

file="$1"

find . -name '*.wav' -maxdepth 1 -exec /usr/local/bin/lame -V 0 -q 0 '{}' \;

for file in *.mp3
do
  mv "$file" "${file/wav./}"
done

To install, download, then open terminal:

sudo install encode-mp3 /usr/local/bin

To use, navigate into a desired conversion folder and type:

encode-mp3

This will encode your .wav files to .mp3

Convert .wav to .mp3 | LAME Encoder Shell Script [md5: 72d4e24f14ea9139136900f2c4281a7f]

[original]

I just wrote a one-liner that will do this for you in Terminal, just cd to the directory of files you want to convert and enter:
find ./ -name "*.wav" -execdir lame -V 3 -q 0 {} \;

iTunes Plus AAC – afconvert Settings Explained

I had the exact same obsession, and ended up creating a FLAC-to-iTunes importer that decodes FLAC files to WAV and imports them into iTunes using iTunes' own encoder: https://github.com/cbguder/FLAC2iTunes

It should be easy enough to modify FLAC2iTunes to support direct WAV input.

As for the soundcheck values, I compared iTunes, XLD and afconvert by encoding WAV files to AAC and decoding them back to WAV and comparing the decoded audio data. I also compared afinfo outputs for the encoded files. While the souncheck values are different for each file, the decoded WAVs are exactly the same, so even if you use XLD or afconvert, the chances are the resulting files will sound exactly the same.

For afconvert, I used the parameters suggested by Apple in the "Mastered for iTunes" guide, with an intermediate CAF file:

afconvert source.wav intermediate.caf -d 0 -f caff --soundcheck-generate
afconvert intermediate.caf -d aac -f m4af -u pgcm 2 --soundcheck-read -b 256000 -q 127 -s 2 final.m4a

For XLD, I used these settings:

Format: MPEG-4 AAC
Mode: VBR (Constrained)
Encoder Quality: Max
Sample Rate: Auto
Target bitrate: 256 kbps
Add gapless information for iTunes: checked
Write accurate bitrate information: checked

Best Answer

Related Solutions

Automator – Converting WAV Files to MP3 Using LAME

iTunes Plus AAC – afconvert Settings Explained

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