Steve: Ive only used the Sinclair so far. Ill need one of those Line In adaptors from Maplins
to try it out on the C64/128 as with the speccys (barring the 2+?)they always had line in. Will try it though as soon as I get it in the post. The ZX Spectrum program I used was the emulator RealSpectrum to create the WAV. Is quite slow as you have to play the entire tape to record it. Would be nice if there was an alternative, all I found were shareware progs however
For the Commodore theres two progs called WavPrg and AudioTap which Ive yet to try. These are freeware
For MP3s, the most useful thing would be a verify program that can leap through the MP3 and compare it to the original data to see if it is all intact. That way you can check it before loading it in. Even better would be a specific MP3 compressor that uses VBR and verifies each block as it encodes. Then it can change the bit-rate for each block until it verifies correctly before moving onto the next one. That would give you the highest possible compression rate.
That indeed would be a v useful program...
Thanks for the info cv643d, and for the links Dizzy