[Flac-dev] Variable Bit Rate

[Masklinn]

On 2011-05-23, at 19:26 , Dennis Brunnenmeyer wrote:
> Is FLAC a variable bit rate format when streamed? If so, how can it be truly lossless?
The same way zip and PNG compression are truly lossless: something can take more space than the information it contains needs.

For instance, take a 1024*1024 completely white bitmap. Your bitmap file is 1MB (1048576 bytes). A good PNG compressor can get it to 200 bytes (this is not a typo: I have a completely white 1024*1024 PNG file in 222 bytes).

Well it's the same with sound (a 5mn track with no sound whatsoever contains less information than "Nun seh' ich wohl, warum so dunkle Flammen"). That's also why the format can't help but be VBR: different pieces of sound contain different amounts of information per second, and therefore have different compression ratio (and compression ratios can — very rarely — go above even 1: white noise is completely incompressible, when you add FLAC metadata you end up with a FLAC file bigger than the source WAV)