ogg: muxing overhead and quality ~ bitrate corresponence

[Doom9]

as the title says.. I'm trying to find out if we can establish some reliable numbers regarding the muxing overhead of an ogg media stream and a quality -> bitrate correspondence for 48khz 2ch ogg files.. so if you have any numbers fire away.

I did a couple of tests with the english and german audio track of bait.. but funny enough even though the wav has the same size.. the ogg file for the english track is smaller than for the german track using the same quality setting which would point to a correlation between bitrate and content.

[-h]

Ogg's quality system works by subjectively deciding how many bits to throw at the audio - I'm not surprised that german speech used more bits than english, it's historically a much harder test for psychoacoustic encoders.

I've seen occasions when quality=3 generated files ranging from between 70 kbps and 140 kbps - all it guarantees is that the resulting audio stream will sound "as good" or "as annoying" as another stream encoded with the same quality setting.

In terms of the quality to use for a movie, I'd encode a 2 or 3 minute segment at varying quality rates, and see which one sounds acceptable to your ears. The final bitrate is extremely hard to predict for music, though perhaps movie soundtracks will be more normalised. I'd still wager that it will fluctuate beyond useful bounds.

-h

[Psyche]

OK, just some numbers about Final Fantasy:

Length: 1:41:38
Audio: Spanish
Quality:2 (Nominal 96 Kbps, not too picky myself :) )
Average: 94 Kbps (close huh!)
Size: 68.7 MB
Video: XviD (this little baby is great!) Quantizer=H.263, MP=5
Video Size: 642364 KB, 627.31 MB (This is what was wanted, Gordian Knot under Video Size)
Final Video Size: 642365 KB (just incredible) (read in VDub)
Final Avi Size: 630 MB

This is something I want to point. AVI incurs in an overhead of some 3 MB just for video (headers, indexes and so on). Doom9 says that ogg+divx overhead in his example is about 2.3 MB but this is PLUS AVI overhead. That means:

Video+Audio size: 696 MB
Final OGG size: 702 MB

Overhead: 6 MB

I just try to say that we should be a little more precise about this. When we say muxing overhead, we mean just video+audio or video+AVI overhead+audio? I think it should be the first one (as AVI is just a temporal container).

In the first case, muxing overhead is just a little over 0.9%. In the second one it's just about 0.4% (as Doom9 says).

BTW, some more thinkings. As audio contents in a film is longer than the average song (except for Jethro Tull maybe :D ) ogg is able to average better at the nominal bitrate. Just a guess though.

[DSPguru]

Originally posted by Psyche
As audio contents in a film is longer than the average song (except for Jethro Tull maybe :D )hehe, i recall this jethro tull album, what was its name.. ? "thick as a brick", right :) ?

[unplugged]

Originally posted by Psyche

This is something I want to point. AVI incurs in an overhead of some 3 MB just for video (headers, indexes and so on). Doom9 says that ogg+divx overhead in his example is about 2.3 MB but this is PLUS AVI overhead. That means:

Video+Audio size: 696 MB
Final OGG size: 702 MB

Overhead: 6 MB


Yesssssss

696 Mb you mean strict sizes read in VirtuaDub "File information".
I can confirm this, in conclusion OGG overhead is much "higher" that AVI.

Originally posted by Psyche

I just try to say that we should be a little more precise about this. When we say muxing overhead, we mean just video+audio or video+AVI overhead+audio? I think it should be the first one (as AVI is just a temporal container).


Not much clear this last argumentation :D but I fine understand what you would say.

[Psyche]

@DSPguru:
Yes! Thick as a brick, one of the best rock albums ever recorded!

@unplugged:
OK, I just wouldn't say *much* higher than AVI, remember that you have to mux audio later in avi, and this takes the overhead up quite a lot. This last specially if you mux VBR MP3, where overhead can be as much as 14 MB, doubling that of ogg.

[DSPguru]

Originally posted by Psyche
@DSPguru:
Yes! Thick as a brick, one of the best rock albums ever recorded!(offtopic) hmm, how about "red" by King Crimson :) ?

[sibe]

(offtopic, too) Hey, there are Jethro Tull and King Crimson fans here, one more reason to like this place :D

Sibe