Great post from Marco Arment on a bug within
AVFoundation that prevents the widespread use of VBR MP3s, specifically for distributing podcasts:
AVFoundation, the low-level audio/video framework in iOS and macOS, does not accurately seek within VBR MP3s, making VBR impractical to use for long files such as podcasts. Jumping to a timestamp in an hour-long VBR podcast can result in an error of over a minute, without the listener even knowing because the displayed timecode shows the expected time.
A lot of my iTunes library is also encoded as VBR MP3s — I was a longtime user of the LAME V0 preset — I’ve seen some weird seeking bugs and other issues in longer tracks. With its ideal blend of quality and file size, VBR a beautiful solution to audio encoding; Apple should provide more robust support for it.