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I ripped a CD to FLAC. Comparing the two versions of the same song with MediaMonkey, I noticed the original CD bit rate is 1411 kbps:

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whereas the FLAC file has a bit rate of 906 kbps:

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Why is this? Is this a loss of data, or just a reflection of the compression (i.e. decompression while playing reverts the bit rate back to the CD's original bit rate)?

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3 Answers 3

up vote 7 down vote accepted

It's just how bit rate is defined. It's "bits of data per second". So if you compress something, even losslessly, it's at a lower bitrate.

The association between "low bitrate" and "low quality" comes from lossy codecs like MP3, which let you trade off quality for file size. Lossless codecs like FLAC instead let you trade off CPU time (at least during compression) for file size.

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Since FLAC by definition is lossless compression there shouldn't be any data loss unless there is an error during encoding.

In my experience, when you compress a WAV file to FLAC it reduces the size by about 1/3. (The FLAC web site claims even better compression, and as @Mulvya pointed out in the comments, this is due to the content of the recording). The bitrate for the FLAC file you have is about 1/3 less than the bitrate of the WAV file.

I would guess that the numbers you are seeing are probably due to the compression.

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The amount of compression depends on the source material. I typically get 80% compression with voice-only tracks. 55% for typical orchestral music, 65% for solo instrumental music, and so on. –  Mulvya Mar 27 '12 at 14:29
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That explains it. The comparisons I made were of recordings of a full band. I guess the cymbals and screaming guitars don't compress so well. :) –  Friend Of George Mar 27 '12 at 14:59

FLAC is Free Lossless Audio Codec where Codec = co mpressor/dec ompressor, so yes the lower bitrate is due to compression.

And yes, the original stream is obtained upon decompression.

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