Help with ac3 files

[jlmiller]

I'm finally able to separate the sound from the vob file (after 10 attempts). But I now have 3 .ac3 files:
movieAudio AC3 T01 3_1ch 32kbps Delay 0ms.ac3 381,434KB
movieAudio AC3 T02 2_0ch 192kbps Delay 0ms.ac3 163,472KB
movieAudio AC3 T03 2_0ch 192kbps Delay 0ms.ac3 163,472KB
Next I ran Nandub, selected the audio .avs file and the sound file to check the Bit Rate Calculator. It was set to 319kbps ran a preview and no sound. I then changed the bitrate to 128kbps (in the Audio box) and still no audio. Where have I gone wrong?

[kaitsuburi]

Originally posted by jlmiller
Next I ran Nandub, selected the audio .avs file and the sound file to check the Bit Rate Calculator.

The above part of your post is confusing. Are you trying to just preview the audio? In that case, try opening the .ac3 file in a DVD player (I use PowerDVD), or through winamp using the ac3 plugin:

http://winampac3.sourceforge.net/

Once you have the ac3 file you want, you would probably want to keep it as it is (to be muxed with your newly encoded video) or you would want to transcode it to mp3/ogg with lower bitrate to save space.

Try rereading Doom9's guides:

http://www.doom9.org/audio-guides.htm

-kaitsuburi

[jlmiller]

I was under the impression I could "preview" both video and sound to make sure they are in sync. Then I need to "compile" the two to make a DivX file.

[kaitsuburi]

Originally posted by jlmiller
I was under the impression I could "preview" both video and sound to make sure they are in sync. Then I need to "compile" the two to make a DivX file.

Your second sentence is on the right track. Put simply, what happens when you reencode/backup a DVD is
(1) you rip the VOBs to your HDD;
(2) you extract (demux) the audio track(s) and create a project file with dvd2avi;
(3) you process the audio separately (unless you want the original ac3 audio -- usually too big for 1 CD backups) and reencode to mp3/ogg using BeSweet or something;
(4) you process the video seperately and you reencode it using the DivX, XviD or other codec;
(5) you join (mux) the separately reencoded audio and video streams into an .avi (or another "container").

As such, you don't need to worry about sync-ing until the very end (step 5) as the audio and video are obviously in sync in the original VOBs (in some very rare cases with multiple separate episodes on a DVD they are not).

Follow the Doom9 guides (Gordian Knot is very beginners-friendly) and you'll get the hang of it very soon. That's where I started not too long ago :D

-kaitsuburi

[jlmiller]

(3) you process the audio separately (unless you want the original ac3 audio -- usually too big for 1 CD backups) and reencode to mp3/ogg using BeSweet or something;
(4) you process the video seperately and you reencode it using the DivX, XviD or other codec;
(5) you join (mux) the separately reencoded audio and video streams into an .avi (or another "container)

I guess I should state I'm using Gnot v0.27.
It is #3 that I'm having a problem understanding (I've read the manual at least 4 times, have it in front of me now, unfortunately it is not too clear as far as manuals are concerned). So, you are saying the audio not only needs to be extracted but also processed. Which apps does the processing though (the Encoder tab in Gnot?).
Is this the same for the video?

[kaitsuburi]

Alright, this makes things easier. In Gknot you can set up your encode so that all the processing (steps 3-5 above) is done automatically for you. Here's a short walkthrough, totally repetitive with Doom9's guide I'm afraid:

1) Look at the BITRATE tab, make sure you've checked "Calculate Frame Overhead" and 1xMP3 (assuming you are doing 1 track mp3 encode) and chosen the appropriate bitrate in the Audio A area (for 1 CD encode, 128 is good, otherwise go for 160). Also in the BITRATE tab, make sure you've input your desired output size (in "Total Size").

2) Next, in RESOLUTION (you must have your .d2v file [what dvd2avi has created for you] open) make sure you have the correct DVD format checked (NTSC probably -- you are from Washington State right?), then the correct aspect ratio (if you are unsure, open your VOBs in dvd2avi again and run preview). In "Crop," put the radio button on "SmartCropAll" and press "AutoCrop" (it will take a moment). Then check your resolution slider. Put it anywhere between width 512 (by whatever) and width 640 (by whatever), for 2CD encode, stay closer to the latter. Check the "Frames" box, you should have 23.976 for NTSC if you've done "force film" in dvd2avi (what are you encoding BTW?).

3) Go to the smaller (movie) window behind the main Gknot window, find the point where your credits start with the slider and press SetCreditsStart. Press on Save&Encode and in the window that pops up put Neutral Bicubic (generally good) in Resize Filter, select "Both" in Trim box (this will encode the credits at slightly lower quality to save space).

4) Continuing straight from 3), leave other options as they are, then select Use 5% in "Compressibility Check" box, press "Now" and wait for it to finish. Now look in the "Bits/(Pixel*Frame)" box at the bottom of the RESOLUTION tab in the main Gknot window. You want a percentage in the range 60-80, so slide the resolution slider until you get a good value in between, perhaps closer to 60% (higher resolution is generally desirable). Don't go over 80%, as you might saturate the codec and get undersize.

5) Repeat 3) (no need to find "credits start" again); but this time leave the compressibility check box in off state. Press Save&Encode, create names for the .avs files, then a new window should pop up.

6)In DivX5 tab, select "Re-Calculate bitrate if needed," "Encode Credits at average quant 20," "Append Credits" and maybe "Delete Intermediate Files" (the last if you are short on HDD space). Make sure "Both Passes" on top is selected. In the Audio 1 Tab (this is where we tell Gknot to do the audio for you), select the Ac3 file you want, then put the radio button on mp3, write in your desired bitrate (see 1) above) and check "recalculate video bitrate" and "delete wav". Go back to DivX5 tab (important!!) press "Add Job to encoding Queue" and either start the encode immediately or add another encode if you need to. Encoding takes a long time and does 2 passes -- between 3 and 8 hours depending on your hardware.

After doing all of this, you will have the final reencoded video (divx .avi) and audio (mp3) streams in your output directory, and you just will need to mux them together, using Nandub/AVIMuxGui/VirtualDubMod (takes 2 min. max) and cut/split the file into CD-sized chunks if you are going for more than 1 CD.

Well, this is too long, sorry. It's all in the guides :)

-kaitsuburi

[jlmiller]

Okay, this time it makes sense. I'm in Western Australia not Washington so I'm using PAL. Since these are for viewing on my PC (99%). I plan to accept the defaults.

Thanks for your help.

I think I can manage from here.