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.
- 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, use a lossless format only if you are publishing music podcasts. When uploading lossless audio, please use FLAC instead of raw WAV files.
- Most podcast and voice content can use lossy compression without sacrificing quality.
- We recommend compressed file uploads at 48kHz sample rate and encoded with AAC-LC at 160kbps.
- We distribute all files as stereo. For mono input we duplicate the audio channel to create stereo output.
- We perform EBU R128 perceptual loudness normalisation at a target of 16 LUFS. (Loudness Range 11 LUFS, True Peak limiting -1.5 LUFS)
- Low quality output formats downsample to 24kHz and 32kHz sample rates, while high quality output uses 48khz.
- The Audio producer's guide to Loudness - http://transom.org/2015/the-audio-producers-guide-to-loudness/
- Mastering for iTunes - https://www.apple.com/itunes/mastered-for-itunes/