Newbie AC3 Question

[brashquido]

Hi There,

Just wondering if it is possible to compress an AC3 track for use in DivX movies while still maintaining the audio as Dolby Digital, and if so how? Thanks.

[Antimon]

Sorta......not sure you'd want to though.

you can only do it if you have a copy of Softencode form sonic foundry which was discontinued...ther eis a guide on the main doom9 site about that...if you dotn have it and can't find it you're out of luck.

but recompresign wotn get you much space before hurting quality.

About all i'd sugest is going from 448 5.1 to 384 5.1 or 224 2.0 ro 192 2.0

if you want to go belove 384/192 compress to oog or mp3 in prologic suround mode.

[brashquido]

Thanks Antimon,

What I'm after is to be able to fit my DivX movies in Dolby Digital 5.1 on a single 99 minute CD. Are you able to convert AC3 to MP3 and maintain 5.1?

[Antimon]

HAHA! sorry *grins*

Good luck withthat, it's not really possible unless it's a SHORT movie.

wait 99 minute cd? cool, whered you get that?

well it's maybe possible but not likly to fit, i've managed 2 hour movie with 192 2.0 ac3 on a 700 meg cd (80 min)
so 99 minuutes thats like what 850 meg? thats only about 500 kb/s for your video stream if it's a 2 hour movie, thats not much.....thats barly enough for a 384x___rip

There is no 5.1 mp3....you can go to dolby surround, whcih is basiclaly a mono rear and no dedicated lfe youdotn lose THAT much...enough midn you but not anythign unlistionable by any means :-)

You could try oog, which does suport 5.1 audio but the playback filters are still very tempermental, and only work with analog 6 channal out cards and amps, *no spdif*

i'd sugjest going 192 kb/s full stereo mp3/oog downmix the ac3 to a 2.0 dolby suround file with besweet and the gui found on doom9, it;s about all you're gonna get on a single cd while maintaining good video. If the dvd has a 2.0 suround ac3 use that and mux it direct, then you wotn have to convert and can still maintian dvd quality

[brashquido]

Thanks again Antimon,

Had a feeling I was trying to have my cake and eat it too! I'll definatley have a shot at the pro logic though.

As for the 99 minute CD's, Tom's Hardware (http://www.tomshardware.com/storage/02q2/020411/index.html) were able to get 900MB on one of these 99 minute CD's! you can get the media here (http://www.blank-cd-cdr.com/product/9099minutes.html).

[Antimon]

Hmm..my drive isnt listed as suported, it's a lite-on 1012b OEM
cool concept though

[cordraconis]

and try to check out the forum about Dolby Pro Logic *2*.

Same as Pro Logic 1, but the rear speakers are Stereo, not Mono.
It is a "Decode only" thing, but some people are trying to modify the encoding process, to enhance the decoding of the MP3.
So if it works, and you use the --alt-preset in LAME 3.92 ...
Why don't you try it ?

I would like to have the .ax decoder dough, but where to errr.. "Aquire" it ???

[brashquido]

Thanks cordraconis, but my Yamaha amp doesn't do Pro Logic 2. I was going to get a Denon that did it, but the salesman said that it wasn't worth the extra money.

I did a few AC3 extrations last night. It seems the AC3 content is between about 6% - 8.5% of the total movie size, making it somewhere around 300-350MB for a 2 hour movie. I'm a bit undecided now. Two 99 minute CD's would be give me a total of about 1800MB which would be plenty enough to have both AC3 sound, and really good video quality in my DivX movies, but has the hassle of being spread across two CD's. One 99 minute CD is enough for pro logic and decent video quality, but quality is going to lack on the 2 CD system.

How many CD's does everyone else put their DivX movies to?

[MaTTeR]

For me, I look at what type movie I'm encoding. If its an action movie and my target is 2CDs, then I use the 5.1 AC3 and burn it on 2 80min CDs.

If it's a drama movie with hardly any surround FX then I'll transcode the AC3 to Vorbis and burn on 1CD.

[Antimon]

It depends for me too....i shoot for 1 cd as often as possible.

which isn't very oten :-)

My first encode was a 1 cd rip of "15 minutes" 192 ac3 2.0 and 520x288 video, fit perfect 699 meg. 2 hour movie

for my second rip, Atlantis, the lost empire, I chose 2 cd. It has the fill 5.1 ac3 and the full 192 comentary ac3 track, full dvd menu's full dvd resolution and all the special features plus the soundtrack and select screenshots. 88 minutes

My last encode is Planet Of The Apes Burtens remake.
again 2 cd's, full dvd res 720x320 full 5.1 ac3 and 1 extra track, but im havign probles, i wanted to include 3 bu t only have sapoce for 2 ac3's and an mp3 or oog low bitrate neither is working, so i'll go to mo=y original plan of just the 5.1 @ 384 kb/s and the dc at 96 kb/s and i have about 100 meg to spare.

so it depends on yoru application and what you want.

15 minutes is near dvd *ie you can't tell on a tv...* and the convience fo 1 cd...

atlatis is 2 but i wanted the extra's..however fi you have 2 cd drives and almost everyoen does 1 dvd 1 cdrw, microdvd will auto switch for you and play from 2 drives continously :-)

[cordraconis]

First of all; Dolby Pro Logic II is also on a PC with a multichannel output, so if your amp accepts 5.1 Ch input, you can decode the DPLII on your PC.

About the encoding of my movies;
I put 2 CD of 700mb, 1 AC-3 track, and subtitles in TXT format. (about 3 languages).
I also put the codec which I used , the DOOM9 audio decoding pack and radlight. --> A 2CD-all-in-one package, so to say.

And for a small movie (no action or not a great AC-3), I use 1 CD with Lame ABR.

Calculations with Gordian Knot, encoding with VDub and 5.01 Codec, And splitting the 1695 MB file with Nandub (use Direct stream copy for Audio and Video, and Select the frame interval for a 698 MB file).

!!! Becouse of the VBR nature of the 2-pass encoded File, your file (you only have to write the first one to see if it has the desired filesize ! (that's a tip ;-) can be a bit bigger or smaller. Adjust the frame interval in Nandub in steps of 1000 frames to get it right.

--> No hassle for splitting AC-3 files for me...

let us know how it goes.