Monday, October 23, 2006

dynamic range compression

I finally bit the bullet today and finished implementing DRC. There are 6 profiles, as defined by Dolby: Film Standard, Film Light, Music Standard, Music Light, Speech, and None.

example using Film Standard:
aften -dnorm 27 -dynrng 0 test.wav test.ac3

example using Music Light:
aften -dnorm 17 -dynrng 3 test.wav test.ac3

The results have not been extensively tested yet, so until then, consider this option experimental. It seems to work ok for the most part, but I have had a couple strange results.

3 comments:

Anonymous said...

Confused about DRC in Aften.
[-dynrng #] Dynamic Range Compression profile
0 = Film Light
1 = Film Standard
2 = Music Light
3 = Music Standard
4 = Speech
5 = None (default)
This is the printed out "help" from Aften 0.05 rev. 246 and in your two examples you're listing "Film Standard" as 0 and "Music Light" as 3.
Even more confusing when using AftenGUI 1.3, the drop-down list selection is sorted this way;
Music Light
Music Standard
Film Light
Film Standard
Speech
None
So, which "pattern guide" is supposed to be the "OFFICIAL COMPLIANT" one?... Could you then please sort it out for me?...

Philippe said...

Hi,

I've tried all different values of -dynrng to some music files and although compression seems to be occuring, I always get some distortion on the compressed parts of the song. I tried playing it with MPlayer, Windows Media Player and PowerDVD, but it's always the same...

Am I doing something wrong ?

Justin said...

Philippe,
You are not doing anything wrong. The DRC in Aften is very rudimentary and needs some work. Basically it does attacks and releases too quickly, so you get some distortion when the audio goes from loud to soft or vice-versa. I would recommend not using until it is improved some more.