Audio Format: Is Ogg Opus an option?

Earlier this year, a colleague suggested that we consider supporting Ogg Opus (an audio codec) in Scripture App Builder. Ogg Opus is supported by Android 5.0+ and iOS 11+.

The audio that comes from Faith Comes By Hearing’s Digital Bible Platform (DBP) is 64Kbps MP3. I know that some people have tested using 16Kbps MP3 and 12Kbps 3GP. Some are OK and some sound really bad when converted.

I need examples of the bad conversions to try these with Ogg Opus at different levels of compression. I would need to know the DAMID of the audio from DBP. Actual audio file examples would be good too as well as documenting the method you used to do the conversion.

For my own testing, I took Matt 1 from Kuna San Blas (CUKNVSN2DA) and converted it to Ogg Opus using the following (on Ubuntu 18.04 with ffmpeg and opus-tools):

ffmpeg -i foo.mp3 -f wav - | opusenc --bitrate NN - foo-NNk.ogg

Here are the results for the sizes:

255K  B01___01_San_Mateo___CUKNVSN2DA-8k.ogg
372K  B01___01_San_Mateo___CUKNVSN2DA-12k.ogg
490K  B01___01_San_Mateo___CUKNVSN2DA-16k.ogg
1015K B01___01_San_Mateo___CUKNVSN2DA-32k.ogg
2.0M  B01___01_San_Mateo___CUKNVSN2DA.mp3

Here are the encoded files: (full names like above) (with shorter names for testing on a device–easier to see the names in Google Drive).

FYI, I did try to use ffmpeg to convert directly from mp3 to ogg. I could play them on my desktop (Mac using Audacity), but they didn’t play on my phone (Nokia with Android 9).

I would like to try this out on some different examples see what results we can get. I would also appreciate feedback on the audio quality of the converted files.

Chris Hubbard