We can make some generalised requirements for getting the best quality out of your podcast audio for online distribution:
- Always record and edit audio in a lossless format like WAV.
- Record in 24-bit samples at a 48kHz sample rate (or up to 96kHz for music).
- Avoid applying heavy limiting and dynamic compression effects when creating your master.
- Keep peaks below -1 dBFS to leave headroom for different normalise and compression operations.
- Don't up sample to a higher rate than the original.
iono.fm Import process
- For uploading your audio into our platform, using a lossless format will always guarantee the best results. Either use the original WAV file, or compress it with a lossless compression codec like FLAC which should save ±40% file size.
- Most podcast and voice content can use lossy compression without sacrificing too much quality. When creating a compressed file for upload we recommend using AAC at 128kbps when the contents are mostly clean recorded voice, 160kbps for lots of jingles or noisy interviews.
- We store the original uploaded files to enable later rebuilding for distribution. Uploading a WAV or FLAC file will store the original as a FLAC file to ensure we keep a lossless copy. Uploading a compressed file will create an archive version using 192kbps AAC.
Our upcoming (v2 August 2017) audio import pipeline will always resample input files to 48kHz stereo if they are not already at that level. No dynamic range compression is performed, but we do perform perceived loudness compression using EBU R128 at a target of -24LUFS.
- The Audio producer's guide to Loudness - http://transom.org/2015/the-audio-producers-guide-to-loudness/
- Mastering for iTunes - http://www.apple.com/za/itunes/mastered-for-itunes/