ultra-low-bitrate encoding advice ?

[Razorblade2000]

Which mencoder filters/params would be good for ultra-low-bitrate mpeg4 encoding? My target would be 300 kbit/s video bitrate and 50 kbit/s audio (vorbis should sound ok I guess).

I THINK I need:
-a denoiser
-a soft blur
-...?

Any Idea?

[Joe Fenton]

That's pretty darn low all right. Using vorbis for the audio is your best choice there... that's probably Q0 or Q1. For the video, use 2-pass xvid and scale the video. Think about it - going from 640x480 to 320x240 cuts the video rate to one fourth for the same quality encoding. I don't see you getting any kind of quality at 300 kbps for large resolutions. Making a lower resolution look better plays back better in my opinion. You should be using b-frames for this as well.

[Razorblade2000]

Thanks :D
I'll try the B-Frame advice (already found out the rest by experimenting :D )

I guess I've gotta try to get real producer working :D
In windows, I could achieve quite nice quality using the 350k template :D

[Joe Fenton]

Yes, some codecs do well at really low bitrates. Real is pretty good. If you feel like experimenting, you could try h.264. FFDShow now decodes that and it's really good for LOW bitrates.

The way b-frames help is that they increase the compression. At the same bitrate, this leaves more bits free for frames needing more bits. It increases the total average RMS error, but free bits are better used elsewhere improving the perceived quality of the video. I usually use 2 b-frames with xvid.

[Razorblade2000]

I'd love to experiment... on a Linux basis :D

I haven't yet managed to get real producer to work :(
Is there a somehow working h.264 codec for linux?

[Joe Fenton]

FFDShow is just the DirectShow (Windows) version of FFMPEG. The latest FFMPEG for Linux should have the h.264 code in it; the 4cc should be 'H264'. Check this thread for more on h.264 -

http://forum.doom9.org/showthread.php?s=&threadid=71396&perpage=20&pagenumber=1