MP3 to FLAC and vice versa Options

[d_headshot]

I heard that when converting between lossy and lossless formats, a temporary WAV file is created and that is encoded to the desired format. If that is true, it is okay to encode from lossy to lossless? Also, which programs allow you to encode back and fourth?

[WonderSlug]

Transcoding from lossy to lossless, i.e. from MP3 to FLAC, means that the FLAC will be no better or worse than the MP3, regardless of the higher bitrate of the FLAC file created.

For example, a 256kbps MP3 music file transcoded to ~700kbps FLAC won't sound better just because it's now at ~700kbps FLAC. It will still sound the same as the 256kbps MP3.

Now, if you take this ~700kbps FLAC and transcode back down to a lossy format, say, 320kbps OGG, MP3, or AAC, it will likely be worse than the original 256kbps MP3 you started with.

Think of it as a Xerox copy of a Xerox copy in that case.

Because the first 256kbps MP3 is the Xerox copy, any ultimate resulting re-encoding to another lossy format is a Xerox of a Xerox.

What you would ideally want is the uncompressed WAV file or lossless FLAC/ALAC/TAK/whatever that the first 256kbps MP3 was created from.

[DVDdoug]

If that is true, it is okay to encode from lossy to lossless?

Right! the losses occur during encoding/compression, not during decoding, and of course there is no additional loss with lossless encoding.

And, the file will have to be decoded/decompressed sooner or later anyway, so there is no harm in decoding to lossless (or uncompressed WAV), and then later playing the lossless file. But if possible, you should avoid re-compressing to a lossy format (or converting between lossy formats) because data is thrown-away every time you compress (with lossy compression).

Also, which programs allow you to encode back and fourth?

I find XRECODE to be very handy. But, there are many other conversion programs, and any audio editor can open in one format, and then save in another.

I heard that when converting between lossy and lossless formats, a temporary WAV file is created and that is encoded to the desired format.

Right! When you convert from a compressed format, the data has to be decompressed first. This temporary data is not always converted to a true WAV file, but it will be decoded to PCM, which is the underlying data-format used by uncompressed WAV files (and audio CDs).

Audio editors also decode the file before editing. So, if you edit and then re-save an MP3, that requires a 2nd lossy encode step. (There are some special purpose MP3 editors that can do some very limited editing without decoding first.)

[greynol]

Right! the losses occur during encoding/compression, not during decoding

Actually losses can and do occur during decoding. A recent discussion unearthed a problem with mpg123, for example, but it is also true with decoders that are not broken. Clipping during decoding is the most obvious example of this. Remember, the mp3 format stores frequency information in floating point.

This post has been edited by greynol: May 20 2009, 22:50

[d_headshot]

Thanks for the replies