GK 0.23, Questions about Sound

[phaysonwulfe]

I have several questions I am looking for answers to, but before I get started I thank the TheWef for his great work and the quick fix on the double pass problem I and many others were having.


Using a normal Divx 4 Double pass schedule.

1. Why is Azid sometimes scheduled and other times not. Also, what does Azid actually do?

2. When do you need to run a compression test. Once, Once per movie, every time you encode??

3. I know that using DivX 4 you cannot use average or variable bit rate, because it is incompatible with VirtualDub. So you must specify that you wish to run the expert string and then change it to read "-h -b 128". It would be nice if GK knew you were using DivX 4 and change the parameters for you. By that just a suggestion.

[pia2001slo]

Answer on 3.question:

Just do audio separatly and then mux video made in Gknot and
audio with Nandub which has VBR mp3 support

Jolly

[Acaila]

Just do audio separatly and then mux video made in Gknot and
audio with Nandub which has VBR mp3 support.

GKnot already does this automatically when you create the standard type of ABR MP3 (and probably also for VBR, but I've never tested that myself).

[phaysonwulfe]

But that defeats the purpose of GK. The automation of the tasks is what makes GK great. Plus, there other problems dealing with sync that I have seen with VBR. Also, Avery Lee wrote quite a bit about vbr, most of it said vbr is good for audio but it us very problematic when you try to mux it back into the video.

[xzquala]

Originally posted by phaysonwulfe

1. Why is Azid sometimes scheduled and other times not. Also, what does Azid actually do?

2. When do you need to run a compression test. Once, Once per movie, every time you encode??

3. I know that using DivX 4 you cannot use average or variable bit rate, because it is incompatible with VirtualDub. So you must specify that you wish to run the expert string and then change it to read "-h -b 128". It would be nice if GK knew you were using DivX 4 and change the parameters for you. By that just a suggestion.

1. azid is an ac3 to wave conversion program. use this, don't let dvd2avi do it for you. one of the nice things is does is raise the volume of the movie without distorting it. a must in my eyes.

2. dunno, I don't ever do one cause I can't do a 100% compression test, only a small sample. if I could do that, then I might consider it.

3. no, really, gknot does this for you, honest. just watch it.

the only real problem with vbr and its variants is seeking, it can be pretty rough for a bit, sometimes it takes the audio a bit to catch up to the video and/or vice versa. but since gknot is doing everything for you as far as making the file, just go ahead and use abr. I do and it does work.

[TheWEF]

Originally posted by xzquala
2. dunno, I don't ever do one cause I can't do a 100% compression test, only a small sample. if I could do that, then I might consider it.

the compressibiliy test actually is very accurate. steady and dividee have done extensive (many days...) tests to find out the best parameters for "SelectRangeEvery". the "small sample" is a very good estimation and representation of the whole movie. the sample size of 13 frames has to do with the gop-lenght of 12 in an mpeg-2-stream.

with a regular comp-test (encode 5% of all frames, compute only 12 out of 13 encoded frames to ignore the "artificial" scene changes) the maximum(!) error of filesize estimation normally stays within a range of +/-5%
changing horizontal resolution 32 pixels up or down normally alters bpp-values more than 10%

so i always do a comp-test. takes 10 minutes, saves me a lot of time.

wef.

[TheWEF]

Originally posted by phaysonwulfe
2. When do you need to run a compression test. Once, Once per movie, every time you encode??

before you encode a movie you select filters,resolution,... based on experience and some rules of thumb.
then you (comp-)test if your selection is a good one.
if yes, you encode the movie.
if no, you change the resolution (or filter,...) and do another test.

Originally posted by phaysonwulfe
3. I know that using DivX 4 you cannot use average or variable bit rate, because it is incompatible with VirtualDub. So you must specify that you wish to run the expert string and then change it to read "-h -b 128". It would be nice if GK knew you were using DivX 4 and change the parameters for you. By that just a suggestion.

it should work without problems. for muxing only nandub is used.

wef.

[phaysonwulfe]

About Question Three,

I initially let GK run using the default(ABR 128) and the movie finished encoding just fine but the audio was messed up.

When I say the audio was messed up, I mean that it would play about 20 secs of audio and then loop back and play it again and again. The video would play great but the audio would be completely wrong. If I moved forward into the movie the audio would change but then it would start to loop again. I remuxed the audio using CBR 128 and the problem went away. I remember reading Lee's comments about different audio settings which lead me to believe that CBR is the only way to get the audio to play/sync correctly. If I am wrong, well it wont be the first time, but I continue you to test and participate in the forum.

Phayson Wulfe,
All Comments are welcome.

[pia2001slo]

Like I Sad..I always do Video with Gknot separatly.I only put
MP3 file into select option so i can get perfect final avi
size (+-3MB). Then I use AZID/Lame 3.91 GUI to create VBR (or ABR) MP3
file (which is just perfect - you must play a little with
settings in AZID/LAME).At Last (but not least) put my Mp3 to AVI
(Caution:delay option must be same as the AC3 file Says) with
NANDUB !! Great movies (well not always), great sound.

Jolly

[jggimi]

Originally posted by phaysonwulfe
...When I say the audio was messed up, I mean that it would play about 20 secs of audio and then loop back and play it again...

The particular avi player being used, (i.e: "The Playa" fromwww.divx.com (http://www.divx.com)) does not support variable bit rate audio. WMP does, as well as some others.