Bonzo3legs wrote: ffmpeg i ATDATA06.HMA -acodec copy MD.wav

Use -acodec copy when you don't want to decode the audio, e.g. if you want to change its container (e.g. .ts to .mp4, .ts to .aac) or filter it (e.g. with -ss and -to). If you want wav output you need to transcode it. ffmpeg i ATDATA06.HMA MD.wav ought to work if it recognises the input format and has a decoder.

I've never used an MD device. I have read that they can hold a few different formats, both 'tracks' and a filesystem - so just like CDs - and that encoding varied as newer ATRAC versions were developed.

ffprobe ATDATA06.HMA should tell you whether ffmpeg recognises the format.

You can use ffmpeg -codecs to list the codecs available. On this machine (using codecs from packman):

ffmpeg -codecs |grep atrac
...
 D.A.L. atrac1               ATRAC1 (Adaptive TRansform Acoustic Coding)
 D.A.L. atrac3               ATRAC3 (Adaptive TRansform Acoustic Coding 3)
 D.A..S atrac3al             ATRAC3 AL (Adaptive TRansform Acoustic Coding 3 Advanced Lossless)
 D.A.L. atrac3p              ATRAC3+ (Adaptive TRansform Acoustic Coding 3+) (decoders: atrac3plus )
 D.A..S atrac3pal            ATRAC3+ AL (Adaptive TRansform Acoustic Coding 3+ Advanced Lossless) (decoders: atrac3plusal )

Note the lack of the E=encoding flag