I would have thought reencoding MP3 to MP4 would lose quality, even going to a much higher bitrate. Why not leave MP3s as MP3s?
That's why it was notable that in a couple of cases where the WAV was corrupt, they kept the original MP3 as being now the 'best available' copy. In no case did they transcode MP3->MP4.
> Some radio broadcasts were stored as mp3 and wav files, with accompanying checksum files. Other broadcasts were only stored as mp3. Before the re-archiving process began, it was decided to generate new MP4 playback files from the wav files to replace the varying qualities of the old mp3 files.
In the cases where we only had mp3 files, the mp3 file was preserved as our master in the preservation environment, with a copy sent to the streaming servers.