Downrate audio?

[CharlyAR]

I own a DVD with a very large audio track, I wonder if there is some one-click soft that can recompress it, because Intervideo DVDCopy and Nero Recode cannot and they give me a 5GB DVD...

Tnx.

[Malcolm]

There are several threads about this topic. Most of them are created by myself. I talked about such a tool/feature with some software authors. Some discussions are still going on.
- doom9: Exchanging Audio-Stream in VOB (http://forum.doom9.org/showthread.php?s=&threadid=75592)
- doom9: AC3 -> MP2 (5.1ch -> 2ch) during Backup (http://forum.doom9.org/showthread.php?s=&threadid=75513)
- doom9: VobBlanker 1.2.0.2 is out: A tool to blank, cut or replace titles (http://forum.doom9.org/showthread.php?s=&threadid=73145&perpage=20&pagenumber=6)
- digital-digest: DVD Shrink quality - Feedback wanted! (http://forum.digital-digest.com/showthread.php?threadid=37290&perpage=15&pagenumber=4)

You can find a manual way to downrate audio explained in the thread about VobBlanker. But it's very complicated!

I hope you will join and ask for a software solution!

I talked with the authors of
- DVD-Shrink
- DVD-Rebuilder
- VobBlanker
- TitleSetBlanker
- ImagoMPEG-Muxer

Also a standalone tool would make sense.

In my opinion, VobBlanker would be the best place so far for adding this feature!

Greetings,
Malcolm

These are my results & estimations about adding such a feature so far:
- DVD-Shrink:
+ would make sense technically (multiplexing code already present)
+ would be very user-friendly
(everything in one place,
preview + balance between space for audio + video,
no multiple copying of several gig DVD Files)
- bound to DVD-Shrink
- a bit out of focus for DVD-Shrink
- DVD-Rebuilder:
+ would make sense technically (multiplexing code already present)
- bound to DVD-Rebuilder
- VobBlanker
+ would be a meaningful addition to the other features of VobBlanker
+ The GUI is already prepared for this feature
(selecting+removing audio streams is already possible)
- the author says he has no clue about multiplexing
- TitleSetBlanker
+ same arguments as for VobBlanker
- ImagoMPEG-Muxer
+ would make sense technically (multiplexing code already present)

[jsquare]

Malcolm,

Lets hope someone will listen to your prayers!

[sweetness]

how much space(file size) can you save form drownrating the audio? and at what cost?
maybe one day this week i'll give it a try.

[Malcolm]

Easy to calculate:
usually, 5.1ch AC3 tracks have bitrates of 448 kbit/s. 5.1ch DTS tracks have bitrates of 768 kbit/s (i think). Concert DVDs with LPCM tracks have bitrates of 1500 kbit/s! If you reencode the audio to 2ch mp2 tracks with a bitrate of 128 kbit/s then you gain the following (assuming you have a 2 hours movie):

DTS, 5.1ch, 768 kbit/s: 563 MB
AC3, 5.1ch, 448 kbit/s: 393 MB
LPCM, 2ch, 1500 kbit/s: 1318 MB
MP2, 2ch, 128 kbit/s: 112 MB

Space saved:
DTS vs. MP2: 563 MB
AC3 vs. MP2: 281 MB
LPCM vs. MP2: 1205 MB

You have to consider the fact that usually people (like me) want to keep multiple languages on DVDs (english, german, director's comment), so the values above count multiple times!
Also if you have bonus material you easily get another 1 or 2 hour of compressable audio material.

i'd say if you have a DVD with 3 languages plus some bonus material it can be up to 1 gig of space for audio that you can save.

The cost?
If you reencode 5.1ch material to 2ch, you loose (some of) the surround information. but since i have no surround speakers, this is of no interest for me.
the quality of the audio material is pretty good, even at 128 kbit/s. Use 160 kbit/s if you're unsure. i bet you won't hear a difference to the original!

The gain?
Up to 1 gig space saved, that you can use for video!

greetings,
Malcolm

[jhmac]

If your going to compress the video and lose quality then down sample the audio and lose quality you lose the whole reason for having a DVD player in the first place. Hell go buy it on video tape and be done with it.

[Malcolm]

@jhmac
Very informative post!
I can judge myself if it's reasonable to compress my DVDs! Actually no one here asked for what you wrote!
Btw. it's not the first time that you gave us such intelligent contributions..! If you can't write something more useful, then just leave it and stop spamming this thread!

greetings,
Malcolm

[TheSeeker]

This can be done as one of the hidden settings in IC 8.3 now I believe as well.. Not sure how well it works but I guess it just downsamples from 5.1 ac3 dolby track to 2 channel ac3 dolby. Not sure on the bitrate.

[DVD_Mickey]

It's true IC8.3 can downsample AC3 5.1 and PCM tracks to AC3 2.0 tracks with 192 KBps. It's done on the fly. The "InstantCopy Audio Transcoder" was not a part of the last update but is a seperate package.

[jsquare]

Originally posted by DVD_Mickey
It's true IC8.3 can downsample AC3 5.1 and PCM tracks to AC3 2.0 tracks with 192 KBps. It's done on the fly. The "InstantCopy Audio Transcoder" was not a part of the last update but is a seperate package.
Where did you get that info from?, I don't see anything on Pinnacle's website about an "InstantCopy Audio Transcoder" package.

[TheSeeker]

Its not its a hidden setting.. not sure what reg key it is at though.

[infoscapeone]

Originally posted by jsquare
Where did you get that info from?, I don't see anything on Pinnacle's website about an "InstantCopy Audio Transcoder" package.

Right, it's not at the Pinnacle site but it is shared in the usual places

[Malcolm]

With the help of a tool from jsoto (PgcDemux) it's now possible to compress audio tracks before shrinking a DVD!
I have made a guide. You can find it here: http://forum.doom9.org/showthread.php?s=&threadid=84887

greetings,
Malcolm

[blutach]

@Malcolm

I have used Besweet to convert AC3 5.1 to wav. Could it then be used to remix to AC3 2ch?

[EDIT} It looks as if this is the guts of your guide[/EDIT]

Regards

[Malcolm]

Basically yes!
Since you are using BeSweet to convert you audio material, you can do everything that's possible with BeSweet!
Btw. you can convert directly from AC3(5.1ch) to AC3(2ch) without creating LPCM / WAV.
Also: I suggest to convert to MP2 instead of AC3! Why? Search for User 'Malcolm'. You will find several posts about this topic (pro/contra AC3/MP2)

The point in my guide is to get the audio-part of a complex DVD (Menues, etc) out in a specific way(!!), convert it to anything you like (AC3(2ch), MP2, LPCM) and then rebuild the DVD structure using the converted audio.
Until now it wasn't possible to demux a DVD with multiple audio-streams, subtitles + menue and remux it back to a working DVD!

In case you have already demuxed you 5.1 material with a different method, then you have to do it again using my method since otherwise you will not be able to create a working DVD again.

greetings,
Malcolm

[blutach]

Thanks for the advice Malcolm. I suspected you could do a direct conversion in BeSweet.

In fact, I have only ever used it once - to extract some music from a DVD - and since my home theatre is 5.1, I like to keep the DTS track and kill everything else (the exact opposite of what people in this thread are looking to do :) !)

Anyway, thanks for your indepth research and to jsoto for his v good progs.

Regards