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.

Sunday, October 22, 2006

build system and other stuff

It's been a while since I've posted. Most of the recent changes have not been made by me, but by Prakash Punnoor, who has nearly completely converted the build system to CMake. The configure shell script is still usable, but once all the features are converted it will likely be removed all together or stripped down to a simpler form and just kept for compatibility's sake.

Also, Prakash has imported an SSE-optimized version of the libvorbis MDCT. The new build system, along with asm run-time detection, have made this possible. The effect is a 5 to 10% increase in encoding speed.