Audio transcoding or re-encoding

[jsquare]

Don't know if this will fit as a feature request for DVD-RB or is there a plug-in for it, but here is my question:

Could the AC3 audio tracks be transcoded to a lower bitrate or re-encoded to MP2 to save space/bitrate for video?

[Malcolm]

Hello jsquare,
please look at the following thread for more: Downrate audio? (http://forum.doom9.org/showthread.php?s=&threadid=79347)
The author of DVD-RB is thinking about adding this feature, but he said this 2 month ago and since then i haven't heared anything new about this topic... It's unlikely that the authors of the other tools will add this feature.

i'd REALLY like to see a standalone tool for this. So i'm able to use different backup tools (DVD-Shrink, DVD-RB, ...)

greetings,
Malcolm

[jsquare]

Thanks Malcolm, from those links that you posted seems like very few people are willing to gave up on audio quality or even touch the original audio track(s), but in our case video is more important than audio.

An 128Kbps 2CH MP2 or AC3 audio track is fine with me specially in low bitrates encodes.

When the cost of DVD-R was high and no transcoder were available I was authoring 3 movies per discs for friends and family with 128K MP2 tracks using TMPGEnc, no one complained about the quality of audio, the surround signal was kept and most people didn't even care as long as the sound wasn't distorted or out of sync.

[SansGrip]

A third-party tool (ala RB-Opt or whatever) to do this is unlikely, since it would be very complicated. The tool would have to pull the original audio from the VOBs and reencode it, then rebuild a new set of VOBs containing the new audio so that DVD-RB would use the new audio instead of the old during rebuild. And even then it probably wouldn't work because the internal structure of the VOBs would have changed so much.

The only option for this kind of thing would be to persuade jdobbs to implement audio re-encoding within DVD-RB. Perhaps a sufficiently large donation would convince him -- question is, how much do you want it? ;)

[jsquare]

Based on THIS (http://forum.doom9.org/showthread.php?s=&threadid=81016) tread the new version of IC8 has a feature that will downsample AC3 tracks to 192Kbps. I tried the register hack based on RB instructions but it failed to work.

If Pinnacle made this "rare" step probably some other transcoders like D2O or Shrink may follow soon.

[Malcolm]

@SansGrip
i was thinking about a tool which only does the demuxing- and remuxing-part. reencoding the audio can be done manually with BeSweet - or alternatively BeSweet can be started from this tools automatically. actually even the demuxing-part can be done before with existing tools. So what's really lacking is a tool that is able to replace/add an audio stream to an existing VOB!
Still, VOBBlanker is my first choice for adding this feature! (Well actually DVD-Shrink would be my first choice. But as a beta-tester for DVD-Shrink 3.2, i know the author quite a bit and i don't see a chance that he will add this feature.. :( )

@jsquare
Thank you for the info about IC8. I don't use it, but maybe this is the kickstart for all the others (DVD-Shrink (i hope), DVD-RB, ...) to add this feature too!!

greetings,
Malcolm

[Inc]

I hope I did catch your purpose well, ....

Is it that what you`re looking for?
http://www.videohelp.com/forum/viewtopic.php?t=234240

It treads about LPCM to AC3 but an AC3 to AC3 reencoding via Softencode or BeSweet/ac3enc.dll would be the same logic.

So as the core of DVDrebuilder is able to parse the Celltimes out of the MovieVOB it should be possible to add a routine where First the movievob would be demultiplexed, the AC3 reencoded and muxed again with correct again assigned stream IDs, afterwards the d2v generating process and all theused routines of DVDrebuilder would follow.

Well such a routine would take an extra full source DVD space amout added to the already needed one as Rebuilder would refer to the audio-shrinked-before VIDEO_TS Set on the HD out of the above mentioned process

EDIT: nope it doesnt have to take a full DVD extra space on HD as it simple could rename the orig VTS_XX_X.VOB to VTS_XX_X.VOB.bak where the new reencodedAC3 containing VOBs with the orig name would be safed into the orig VIDEO_TS

?

BTW: As many menues do take a very big amount of DVD space (like long motion ones) there should exist an option where a forced VTS_XX_0.VOB "transforming" via Rejig should be done.
I still do that via ShrinkDVD before but could be integrated into Rebuilder.

[SansGrip]

Originally posted by Malcolm
i was thinking about a tool which only does the demuxing- and remuxing-part.
It's the remuxing part that makes DVD-RB so cool. It's an extremely complex process that's difficult to perfect, as the number of bugs tracked to slight timing errors in the rebuild phase testifies. If someone wrote completely correct remuxing code then he's already written a significant proportion of DVD-RB, since it's much easier to demux than remux...

[Malcolm]

@SansGrip
You are right! :)
complex stuff this muxing thing. Most of it is already present in DVD-RB. That's why i wanted jdobbs to extend DVD-RB for the audio-replacement feature! jdobbs already has to multiplex a) the new (compressed) video b) all existing audio-streams c) all subpicture streams. So it shouldn't be a problem to replace one of the audio-streams with an external one and multiplex this one to the final VOBs! (I think..)

@incredible
Thank you for your link. The problem is
a) it has to be done manually
b) it only works for a single audio-stream

but thanks anyway!

greetings,
Malcolm

[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

[pg55555]

Malcolm

Do you think your guide can be used to solve some of the audio dropout problems some users experience with RB?

I mean, the audio dropout has been resolved in some cases by demuxing / remuxing. But all cases I've read imply using Remake or DVD LAB or Scenarist, all payware.

Your method use all freeware. In fact, as I'm proposing not to compress the audio, a couple of steps would be not necessary

[Malcolm]

i heared of these audio dropout problems with RB. But since i'm not using RB, i can't tell if my guide can help here.

at least with jsotos help and my guide it IS possible (for the first time) to demux/remux a DVD using
a) only freeware tools and
b) keeping all audio, subtitles and menues intact!

Just try it and tell us your results!

greetings,
Malcolm

[Sir Didymus]

Hi Malcom :)
Your method is beautiful. I catched it when you posted in the Ifo/Vob Editors forum and I was amazed about it. Thanks to two grat programs from Jsoto (PgcEdit and VobBlanker) you have bee able to address (and to solve, a would say) a very very big and relevant problem in the squeezing a DVD: to compress also the audio streams. This is fantastic. THANKS A LOT FOR GIVING TO ALL OF US THIS NICE POSSIBILITY...

@pg55555.
I can say NOTHING about the dropouts. On the other hand I can GUARANTEE that the Malcom's method is basically re-authoring the titles using IfoEdit or Rejig, and this may have an impact changing the usage of the STD buffer of the video stream. This is due to the performed re-authoring is changing SCR timings (and many other things) inside the cells of the VOB files. On the other hand (see the thread "Dropouts - Jdobbs don't bother reading...") the authoring performed by these two applications has been tested and - I say explicitely: I am concerned only to the usage of the STD buffer - I am not very happy about...

Just my point of view...
SD

Edit: and of course these applications have big limitations on their authoring capabilities (no multiangle, no BOV support for example). This is totally understandable, due to they aren't full authoring packages...

[pg55555]

Sir Didymus

I'm aware of the limitations. But for people that are experiencing audio dropouts and do not have (or do not want to pay) access to others tools, Malcom's guide is worth a try. Most DVDs do not have multiangles


As I'm not experiencing audio dropouts (fingers crossed :) ), I can not test it.

[jdobbs]

Sometimes I wish I'd never even responded to these audio dropout posts, because I'm tired of hearing about it. How many of you who are posting in this thread have ever actually had one?

And I swear -- if I hear from one of those same 10 or so people posting in this thread (to get their point across AGAIN) I'm going to go ballistic.

Best advice: If you don't like DVD-RB, use something else. I personally use it only for one reason --> it gives me the best backups i can get (much better than any commercial package) -- AND I NEVER, EVER, EVER, EVER -- GET DROPOUTS.

[lamster]

Well, all my audio problems have been solved by the latest DVD-RB releases. But I still might be interested in the ability of down-sampling the audio if it freed up a significant amount of space for the video... (Particularly if this was supported by DVD-RB.)

[DD51]

AND I NEVER, EVER, EVER, EVER -- GET DROPOUTS.

You know I never write here:o ...
Just wanted to say "ME TOO";)

Regards,

[pg55555]

jdobbs
I'm going to go ballistic

Sorry if I'm the culprit of your reaction (I am the one that introduced the audio dropouts issue in this thread)

My intention was to make a contribution to the RB community, not to imply in any way RB was an inferior product.In fact I believe it is a spectacular piece of software and that's the reason I try to assist others to get the most of it.

I use RB for practically all my backups (around 180 up to now)and have not experienced audio dropouts. The only time was in a backup with the ill fated version 0.61 (or 0.60?) and it could have been a media problem :(.

I can understand your frustation: how to solve a bug (if it exists at all) that you can not reproduce?

Pablo

[Malcolm]

o.k. since it's pretty off topic and no one really can say something valid to this audio dropout problem, i suggest to just stop discussing it here. ;)

greetings,
Malcolm