ac3's are too big. Can a wav = stereo srrnd?

dornier wrote on 11/30/2006, 3:57 PM
I've got 14 audio files that were transferred from 1974 audio casettes, cleaned in Audition and saved as .wav files.

I'm trying to include these on a project's disc that is already getting full.
Three of the files are over 27 minutes. I think going to ac3 would make these things MUCH larger than I can afford.

It's a 5.1 audio project, mostly for the fullness (only a few pannings) and also because I don't have room for multiple soundtracks. Would DVDA play the wav files in "stereo surround", using all the speakers, if I didn't render them into ac3?

Thanks.

Comments

ScottW wrote on 11/30/2006, 6:50 PM
Why do you think AC3 would be larger? AC3 is usually highly compressed, especially compared to PCM in a WAV file which is not compressed.
dornier wrote on 11/30/2006, 7:40 PM
Well I rendered an mp3 out to ac3 and the increased by a factor of 4x. I tried lowering the bitrate, but vegas gave me warnings DVDA might not like it. Actually, it concerned being playable on DVD players.

If I thought the mp3s that I have could produce through all the channels (no panning needed) I'd leave them the way they are.

richard-courtney wrote on 11/30/2006, 8:06 PM
Would a technology like Dolby Headphone give you the 5.1 feel without actually
adding 4 additional channels?

see (hear) this site's demo....
http://www.bit-tech.net/bits/2006/11/18/Dolby_Headphone_demos/1.html

EDIT: or Dolby Virtual Speaker
http://www.dolby.com/consumer/technology/headphone.html

It is not part of DVDA or Vegas so you might need to rent the hardware to encode.
dornier wrote on 11/30/2006, 9:13 PM
The display will be a TV and DVD player.

I guess my question is this:

If I take an mp3 and stick it into DVDA (a 5.1 project), and the mp3 has no specific 5.1 mixing, will I at least hear the mp3 in all the channels equally? (frequency limitations for sub-woofer notwithstanding).

That's the essence of it.

The reason I ask is that the MP3's (haven't gotten to my wavs yet) are HUGE when rendered out to ac3...a factor of 4.
TheHappyFriar wrote on 11/30/2006, 9:55 PM
no. if it's stereo it only plays in two speakers unless the sound system is rigged funny. for 6 speaker you need ac3 or dts on a dvd.

you need to actuatly test things before you make assumptions. i just made a 2 channel wave & a 5.1 surround sound ac3 file.

the wav = 51mb
the ac3 = 14mb
the mp3 = 6mb.

that's not even close to 4x bigger.
bStro wrote on 12/1/2006, 5:16 AM
The sound system doesn't need to be "rigged funny." Most multi-channel receivers (5.1, 6.1, 7.1) have several "surround sound" settings, most of which will distribute a stereo signal among the other speakers as well (keeping left on the left and right on the right). It wont' be "true" surround sound (ie, he can't pan from, say, FL to RR without also panning to FR), but he doesn't seem to be concerned about that.

Rob
bStro wrote on 12/1/2006, 5:22 AM
Well I rendered an mp3 out to ac3 and the increased by a factor of 4x.

Okay, but what was the bitrate of the original MP3 file? Generally speaking, there's not a whole lot of size difference between and MP3 and an AC3, so long as they're using the same bitrate. Unless the AC3 file is encoded in 5.1. If you're not really taking advantage of 5.1, don't bother using it.

Rob
richard-courtney wrote on 12/1/2006, 6:53 AM
I am wondering if noise in the MP3 is causing larger than normal AC3 files.
If you apply some filtering in Vegas does it make the files smaller?

You really should not be getting larger than the original wavs as it is compressed.
That is why most of us use AC3s (note 2 channel stereo with a few occasions 5.1
for fun) to leave more space for longer video.

Since you don't need 6 channels all the time Dolby Headphone or Virtual Speaker
would be ideal. The steam locomotive example is my favorite.
John_Cline wrote on 12/1/2006, 7:32 AM
"I am wondering if noise in the MP3 is causing larger than normal AC3 files. If you apply some filtering in Vegas does it make the files smaller?"

No, filesize is determined entirely by bitrate. A 192kbps MP3 will be the same size as a 192kbps WMA or a 192kbps AC3 file.

I suspect your MP3 files were created at 48kbps and, since DVDA encodes the .AC3 stereo audio at 192kbps by default, the files are 4 times larger. If you were to convert the MP3 files to uncompressed .WAV format, it would end up being 32 times bigger than your original files.