Howdy all,

I was wondering if anyone had run some tests already (before I do) on how your lossless compression level influences the speed with which you can convert from lossless to lossy.

For example, does it take longer to compress a FLAC -8 file than it does a FLAC -5 file? Does the lossless file have to be decompressed before it can be compressed to lossy, or is it more of a direct path?

The settings and codec used will often determine the time needed to convert to lossy.

In the case of FLAC there are no such issues. According to my tests FLAC -8 will decompress as fast as -5. if there are any speed differences they should be minor - the time taken to encode is more likely the bottleneck.

The lossless file will need to be decompressed before conversion, but can be done in one process by the converter. I.e.: you do not necessarily need to decompress to WAVE before converting - an application like foobar will decompress and encode in one move, either by piping the decoded data or using a temporary wave file.

Thanks! Very interesting that the decompression times are not as variable for FLAC.

I'm interested in this because I have always ripped straight to LAME and am gearing up to get a new HD and make a complete lossless archive of my CDs so I can rip to whatever lossy codec I need in the future.

It seems to me it would be worth my while to just use the maximum compression for my lossless files based on what you are saying.

You will gain about 0.3% of compression by using FLAC -8 instead of the default(-5) and FLAC -8 will take about a little over 4 times as long to encode as the default. This is about 1.6MB savings for a 400MB image file. Because of this, then i use the default, but if you don't mind the extra time and thinks that the 0.3% compression gain is worth the 4x extra encoding time, then use -8 And as Synthetic Soul said, then decoding time differences between the different compression modes is neglible.

Well, I used FLAC as an example because I'm most familiar with it, but your point is well taken, Martin. I have always felt that Josh chose -5 as the default because he felt that it was the best tradeoff in terms of speed/compression ratio.

At this point, I'm just gathering information before I begin the process. I have experimented with wavpack and I'll most likely check out TAK while I'm at it.

The fact that higher compressed files decode at the same speed only applies to FLAC. Files compressed with Monkey's Audio or OptimFrog decode a lot slower at higher levels.