Any difference between FLAC level 0-8?

2009-10-15 21:28:19

Forgive me if that has already been asked...did a search and could not find it.

When using the FLAC Frontend to encode files, is there any difference other than file size or compression ratio in selecting encoding level 0-8? Which one would yield the smaller file size and would a higher amount of compression result in any file errors/corruption in anyone's experience?

Thanks.

Any difference between FLAC level 0-8?

Reply #1 – 2009-10-15 21:41:16

Speed is another difference. Level 0 would be the fastest.

Any difference between FLAC level 0-8?

Reply #2 – 2009-10-15 22:18:09

FLAC is lossless, so no corrupt files should be produced. That ought to be well tested by now.

Essentially, higher levels use more computationally intensive processes to search for better predictors and lossless coding schemes for the audio in question. That can add enormously to the encoding time, usually for no more than 1 to 2% gain in compression ratio. FLAC is asymmetric, meaning that it's designed such that decoding is very fast regardless of encoding time.

For the main libFLAC -5 is good and fast, a real sweet-spot. -8 is a good deal slower but in return might gain only 1-2% in compression ratio. With other branches, like FLAKE I'm not so sure of speed, and the equivalent settings are over a different number range.

Another small difference, apparently, is that at low settings (up to -3, IIRC?) the encoding can be performed in integer arithmetic, potentially suiting hardware-embedded applications. All settings use integer decoding to ensure losslessness.

Any difference between FLAC level 0-8?

Reply #3 – 2009-10-15 22:18:19

http://wiki.hydrogenaudio.org/index.php?title=Flac

FLAC compression levels go from 0-8.  0 is the fastest to encode, with the least compression.  8 is the slowest to encode, with the most compression.  The compression gains of level 8 over the default of level 5 are often deemed to be inconsequential.