Question of the Month: Lossless Conversion

Question of the Month: Lossless Conversion
Q. Is there a way by which the MP3 format can be converted to a lossless format in the true sense? What is the best method of converting analogue signals to a digital format without compromising fidelity? — —B.P.B.

Analogue media

A. Thanks for your interesting email questions.

The answer is no, an MP3 file by definition has already thrown away a great deal of data that cannot be recovered.

To convert analogue signals to a digital format without losing data or compromising fidelity, you have to use a WAV or AIFF file format. Either of these will preserve the PCM data stream and introduce no compression or losses, but the files will be large—about ten times the size of a lossy MP3 file.

That said, there are several lossless compression formats that will use much less space, and preserve audio quality. The space reduction is about two to one, so the files will be about half the size of a WAV or AIFF file. They are FLAC (Free Lossless Audio Codec), Apple Lossless (ALAC) or WMA Lossless (Windows Media Audio Lossless).

You must start with the original signals, either analogue or a digital PCM bitstream from a CD. Encoding those signals in FLAC, ALAC or WMA (Lossless) will not compromise fidelity or throw away irretrievable data.

I'd also add that if you run MP3 at relatively high data rates such as 320 to 360 kbps (kilobits per second), the audio quality will be very good for all but a few esoteric instruments (harpsichord and castanets). I can say this with some authority, as I was a member of the listening panel auditioning many lossy and lossless codecs 15 years ago for the Canadian Broadcasting Corporation at the Department of Communications in Ottawa, Ontario. The experiments conducted in Canada were repeated by the BBC in England and ABC broadcasting network in Australia and reached the same conclusions as the Canadian listening panel.

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