Hi,
Today I compared severel audio tracks. I didn't have an ac3 2.0 so I took a mp3 issued from an Xvid, encoded in dolby surround, that I'd decompressed into WAV using virtualdubmod.
This is what I compared on my amp, DPL mode and bass management ON for 2.0 tracks and AC3 for 5.1 track.
1/ original DS PCM WAV
2/ mp2 at 128 kpbs produced by besweet
3/ ac3 2.0 at 128 from Besweet
4/ ac3 2.0 at 128 from ACDTools
5/ ac3 5.1 at 384 from ACDTools
3 and 4 are the worst choice. The audio quality is not in cause but there is a big level drop very noticiable when you switch the track (even is this is not so obvious on the PC)
High freq in 2 have a lesser quality then in 1, but it is not a surprise. 1 has the best high freq compared to all others. It's not only due to what Inc discovered there :
http://www.kvcd.net/forum/viewtopic.php?t=15987.
Now the things that is the toppic of this thread : what about 5 compared to other tracks ?
Well, first I didn't have an ac3 2.0 as source, and as tell above 3 and 4 aren't good, so I can't compare directly 2.0 and 5.1 but I can dfo for mp2 and ac3 5.1 (tracks 2 and 5).
- 5.1 produced ACDTools is not pleasant at all ! Too much informations that belongs to front row go to rear one. Especially voices. That makes the dialogs hard to be distinguished from the ambiant music. Very tiring...
mp2 result is better about front/rear. But if you compare only the front line, there is a little bit too much things on the central channel. This time this is the music that is covered by the voices and the "width" of the audio field is narrower (eyes closed, you don't feel the sound the same way. 5.1 is more pleasant, more "opened").
Also the low frequencies are better with 5.1 than with DPL. They are more punchy, more "dry". This can be due to the poor bass management of my amp (Sony's is good for that).
So finally ? I'll keep my mp2 as best choice but what ACDTools produce can be interresting if you have some free room on the disc after you had encoded the m2v.
note : filesizes are 85 MB for 128 kbit/s tracks and 256 MB for the 5.1 one.