Benchmarking lame presets
Posted by micele - 03/09/09 at 08:09:12 am
As some of you may now, I maintain a very well-regulated audio collection. Some month ago I decided to entirely kick mp3 and from now on just accept FLAC files as valid extension to this collection. Reasons for this decision are not described in one or two sentences so maybe a post on this topic may follow in good times.
However, due to the limited FLAC support for audio hardware (such as *PODs, car radios and so on) I’m still reliant on transcoding my FLAC files to mp3 if I wanna use them with such devices. Since CPU power doesn’t matter nowadays that’s not a real problem. The transcode process doesn’t comsume much more time than the actual file transfer via USB2.0. For sure I use the best mp3 codec available: lame.
Lame implements a huge list of so called presets, which have been developed further in the last years. Without discussing the presets in detail (a corresponding discussion can be found here), presets have to be understood as different quality levels the final mp3 is encoded. As these presets have been going through a process of refinement, different types of usage and labels have come up.
It seems obvious that new and old presets have been linked internally and not all different types of presets and codec switches implement exclusive algorithms. So I did a simple benchmark in order to find out which presets/options actually have to be understood as an unique preset and which link to another one. Of course I’ve been also interested in the speed/efficiency ratio! For the test i compared the “standard” and the “extreme” respectively the V2 and V0 preset as these are most commonly used. The results are quite evident and are listed below.
Setup:
- codec: lame 3.98.2
- OS: Linux 2.6.29
- CPU: Intel L2300 2x (1500MHz, 2MB)
- Testfile: WAVE (60MB), Tracklength: 5:25
Results:
| preset | time consumed | file size | md5sum | header entry |
|---|---|---|---|---|
| –vbr-new -V0 | 29,40s | 10763184 | 6be8….ea37 | -V0n |
| –vbr-new -V2 | 28,81s | 9258816 | 0915….cd2d | -V2n |
| -vbr-old -V0 | 39,80s | 10590624 | 151c….9071 | -V0 |
| -vbr-old -V2 | 41,20s | 8872680 | f802….9073 | -V2 |
| –preset fast extreme | 29,41s | 10763184 | 6be8….ea37 | -V0n |
| –preset fast standard | 26,38s | 9258816 | 0915….cd2d | -V2n |
| –preset extreme | 39,21s | 10590624 | 151c….9071 | -V0 |
| –preset standard | 40,69s | 8872680 | f802….9073 | -V2 |
The results look pretty obvious. It seems that internally –vbr-new is identical with –preset fast and the same is true for –vbr-old and –preset. So in other words, the old scheme –preset isn’t used anymore respectively there is always an equivalent for the old and the new preset style.
I still own old mp3 files where header fields say “aps” for “alt preset standard” or “ape” for “alt preset extreme”. However mp3 files encoded with current versions of lame will always be marked with the modern vbr-new style, which is also an indication that the old presets don’t have exclusive relevance anymore.
Furthermore it can be seen, that the new algorithm user by –vbr-new and –preset fast is significant faster (around 25-30%) with slight losing in compression efficiency.
Of course all this is not representative on a large scale but it gives an idea of differences and ratios of different preset types. But for all that FLAC should always be first choice for audio encoding, since good music doesn’t deserve to get encoded lossy 
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