Think about it... AC3 downsampling/reencoding

[DaRtHmAuL]

Hi guys,
i've just though about a way to reencode AC3 audio to work with DVDRebuilder. I may be wrong but give it a try.
Well, we can use the BIG3 method to demux (prefered by PGC) until the encoding (BatchCCEWS) step we won't follow.
Then, run your favourite AC3 encoder/transcoder like BeSweet (works bad on AC3) or AC3Enc (included in Scenarist)... refer to others guide to do these audio steps.
We finish in generating our scenarist script with ScenAid (We have to choose to keep original assets) and then reauthoring as usual with scenarist.
This trick is for person who knows BIG3 very well and audio encoding as well because i'm not giving too much details... i assume.
But if the trick works, i'll wrote a guide.
I'll let you know.
cya

[colinhunt]

I can't think of a single valid reason to start downsampling Dolby Digital soundtracks for DVD-5 re-encodes. The space saved by that would be negligible to say the least, and you'll only f*** up the sound even more. 384kbit for six-channel Dolby Digital is already combining high frequencies and sounds muddy.

.:colin

[nwg]

The only time when I re-encode audio is when I want to use DTS.

I re-encode Ac3 5.1 to 2 channel and then mux it with the video and DTS track. However, the way I do it I lose the menus and subtitles.

I get about another 200MB of average more space back.

[Fr4nz]

Originally posted by DaRtHmAuL
Hi guys,
i've just though about a way to reencode AC3 audio to work with DVDRebuilder. I may be wrong but give it a try.
Well, we can use the BIG3 method to demux (prefered by PGC) until the encoding (BatchCCEWS) step we won't follow.
Then, run your favourite AC3 encoder/transcoder like BeSweet (works bad on AC3) or AC3Enc (included in Scenarist)... refer to others guide to do these audio steps.
We finish in generating our scenarist script with ScenAid (We have to choose to keep original assets) and then reauthoring as usual with scenarist.
This trick is for person who knows BIG3 very well and audio encoding as well because i'm not giving too much details... i assume.
But if the trick works, i'll wrote a guide.
I'll let you know.
cya

There's no reason to resize an AC3 track because you would save few bytes and the quality loss would be bad.

[DaRtHmAuL]

Yes, it's a personal choice of course but it's not the point.
You can save 200-300mo if you downsample 2 ac3 tracks 448kbits into 320kbits and the quality is pretty good at my experience with AC3Enc, not BeSweet!
It was just a simple idea for those who wants to do this. By searching in this forum, i saw some threads about it... that's why i wrote this one.
But in most case i agree with all of you... the gain is negligible.
cya

[Fr4nz]

Hey you can use AC3Enc also with Besweet...

[DaRtHmAuL]

Yes
when reencoding ac3 track i use BeSweet to convert the original dd5.1 file into 6 waves and reencode them with AC3Enc. It works flawlessly.

[nwg]

I use Besweet with AC3MAchine.

[wmansir]

Why not just do the BatchCCEWS step and not use DVD-RB at all?

[Tiamat]

or why downcode at all, sound makes a huge difference in a movie! I always go with DTS so to reduce the quality of DD seems like a bad idea.

[DaRtHmAuL]

Well well well :)
@nwg : that's why i purpose this idea... to preserve the all DVD things.
@wmansir : and yes! This is faster to proceed with BatchCCEWS if we start with BIG3 at begining. There is no big advantage to do all these steps to just reencode the audio for DVDRB, i know. it's just a trick...
@Tiamat : It's a good deal to reencode the audio when you deal with a long movie like Nixon. I personnaly don't need to preserve a 448kbits audio for a movie like this one because there is no big sfx effects but just speech.
Voila
Thks all for sharing your point of view.
cya

[Jester700]

I'll agree that downsizing AC3 doesn't make much sense, given the small gains and the quality loss. But I would LOVE to be able to encode a PCM soundtrack as AC3. I have several concert vids that have Dolby 5.1 and stereo PCM, and I'd love to keep that 2 channel track on my backup, but don't want to use all that space for PCM.

[DaRtHmAuL]

You may be able to do this using the trick...
let me know if you have enough time.
cya