Should I use AC3 or Vorbis?

[scottws]

I was reading on Hydrogen Audio's forums that for 5.1 channel sound, you should just stick with AC3 over converting to Ogg Vorbis.

I've been encoding all my movies with DVD2OGM and have been using Vorbis for the audio. I didn't even think Vorbis could do 5.1 yet, but apparently it can. I haven't been downmixing any of the Dolby Digital tracks, so I guess I have 5.1 Vorbis sound in my OGMs. I should have been downmixing, because I don't even have a 5.1 setup on my PC, and don't have my PC hooked up to my home theater system.

Just now, after reading that HA forum thread, I went into DVD2OGM and picked the AC3 radio button instead of the OGG button and saw that the video bitrate jumped UP. I figured at q4 Vorbis, it would be a lot smaller than AC3. I guess not.

What do you guys think? Stick with Vorbis or just mux the AC3?

[sergelac]

i have no preference, AC3 or OGG, both are good.

you should not do downmixing,
i have only stereo headphones and the sound quality is better with 5.1 than with stereo,
windows does a very good job of downmixing on playback

[scottws]

I've decided to stick to Vorbis. A bug in the bitrate calculator of DVD2OGM led me to believe that AC3 and Vorbis were about the same filesize, which isn't the case. AC3 is much, much bigger.

Thanks for the tips about downmixing.