Hi,
has anyone worked with the command line "afconvert" utility to compress WAV or AIFF to AAC/MPEG4 audio?
I've been using OGG Vorbis mainly and never had any phase issues.
The m4a audio files sound good, also confirmed by Hydrogenaudio's blind tests but...

The files encoded with afconvert though have about 1100 samples silence at the beginning of the encoded file.
Does that sound familiar to anyone?

What's the fix?

Thank you!

 

vorbis has phase issues at (really) low bitrates

try qAAC instead. Or maybe it's a problem with your AAC decoder.

 

Last edited: May 18, 2020

I guess so. Shouldn't happen. I'll try a different version and if all fails, fall back to qaac.
Maybe nobody cared because in 99.9% of the cases, people use it for songs, not samples.

 

Update, in case anyone runs into similar issues:
In fact, every AAC encoder introduces an offset in the encoded audio file.
It's called "priming" and the length of silence at the beginning depends on the encoder and the sample rate, for example.
Encoders usually include information about the offset in the file header and it's up to the decoder or player to evaluate this information.
I had opened my AAC-encoded files with an older version of Ocenaudio which does not evaluate this information and shows some silence at the beginning of the encoded file that's not present in the source WAV file.
If you load the mp4 audio file in a program or app that's built correctly, it will skip that offset.