Don't use the default setting for ac3. Do a search to see better encoding results. ac3 should be better than wma. Most of the default settings are dumbed down.

The obvious reason to use AC-3 is to reduce audio file size. PCM runs about 1,500Kb/sec, while AC-3 stereo is just 192Kb/sec. If you're putting more than, say, 75 minutes on a single-layer DVD you'll be able to take advantage of the lower audio bitrate to increase the average bitrate for your video.

What kind of quality hit do you take going with AC-3? Why not find out for yourself--take a short PCM audio clip and throw it on the timeline. Do an AC-3 render of a copy of that same clip and put THAT on the timeline also, directly underneath the first one. Sync them up precisely and match levels precisely. Then play them while inverting the phase of one of them. Whatever leaks through represents the amount a degradation caused by the AC-3 encoding.

ac3 strereo @ 192 is runnign a full 20khz bandwidth, which is almost identical to the 5.1 variant.
To the naked ear, its unnoticable save for compression (ie dynamic range compression) ratios if used within the encode

the ac3 encode algorythms are too precise for the human ear (or any consumer sound system) to discern, so i see no benefit in using PCM unless its been specifically requested..

Sorry, but I have to disagree with you on this one...Listening to the audio on a high quality sound system will definately reveal differences between PCM and AC3 encoded audio. Even my old ears can hear the difference :)

Any algorythim that throws away audio information is going to be noticeable at some point in the process...

I did a demo/test with a group of sound engineers many years ago, testing the sonic quality of some studio quality analog to digital encoders...Using an A/B/X switch in blind testing, the audio engineers picked out the correct source path 100 out of 100 times...Granted, these guys all had "Golden Ears", but it was enlightening to participate in the test, and to discuss the findings with these guys, as well as what they were acually hearing that clued them in.

Having said that, I find that AC3 is acceptable in almost all circumstances, but if I have the space for PCM on the final disc, I use PCM just to get the best audio I can...Personal preference I guess...

Cheers!

Sorry, but I have to disagree with you on this one...Listening to the audio on a high quality sound system will definately reveal differences between PCM and AC3 encoded audio. Even my old ears can hear the difference :)

IF you have speakers that can produce the difference. :) Studio monitors normally can but many consumer speakers can't.

That's true...Imagine how it sounds with a 3" speaker built-in to a portable TV...No quality there...LOL

I'm finding that generally, consumers are getting to be more aware of audio fidelity as it relates to the improvements in video quality...The bigger screens are getting somewhat better audio treatment, and a lot of people do what I do which is to run the audio into my home stereo system (5.1), that does in fact, have very high quality speaker and amplifier systems.

Cheers!

I try to use PCM when I can, but you have to be careful about exceeding the bitrate with your video. I have done that a few times without thinking about it.

Dave T2

At 192kb/s very few people can tell the difference between Dolby Digital and PCM, but to account for those who can, it's simply a case of upping the bitrate. Use 224kb/s or higher and nobody will be able to tell the two apart.

Conversely, most people, even on small TVs, will appreciate the additional 1Mb/s you can dedicate to the video.

Lots of good tips and insight. Thanks for sharing, everyone.

Agreed, video bit rate needs to be as high as format specs will allow along with the encoded audio...

We have a couple of Toshiba stand-alone Hard Drive/DVD Burners here at the station where I work (used for a variety of uses, but primarily for making sales presentations)...Before I got here, they were having a devil of a time with DVD's they'd make not playing on stand-alone DVD players...They didn't have a clue as to what the problem was...After a few minutes of analysis, I determined that they were using a default bit rate preset for the DVD's that recorded at 16Mbs! The DVD's would obviously play fine on the Toshiba that recorded them, but would rarely ever play on regular players...When asked why they recorded at such a high bit rate, the answer was..."Higher bit rates means better quality doesn't it?"...I explained the problem to them that they were exceeding DVD format specifications, and created a new preset for them that keeps the average at about 8Mbs, and now everything works reliably on any DVD player they take it to...

Format and standards ignorance can make even the brightest professionals look bad...

I'm now having them use real DVD authoring software on stand-alone PC's with burners to make better, more professional discs that can handle diffferent aspects and display requirements.

I got saddled with the training on this (even though it's not my responsibility), because I knew what I was doing, and no one else around here really did...So now, even when I'm up to my proverbial in alligators on engineering matters, I sometimes have to stop what I'm doing so I can bail them out on a problem so they can finish their project...

I do it with a smile, and just add another deposit to the Kharma Bank.

Cheers!

How much cost would DTS encoding add to Vegas I wonder. It's supposedly better quality than Dolby Digital, but still offers better compression than PCM. And it's 5.1 capable.

It would be nice to have DTS as an option, however I wouldn't want it bad enough to add to the cost of Vegas.

Well, would you look at that! ...I just found this on the DTS web site.
http://www.dtsonline.com/pro-audio/3rd.php



On the the DTS 3rd party product list. Down at the bottom is Sony Creative Software. And it talks about a blueray encoding system.

Sweet.

"Supposedly" being the operative word. Consumers have been confused by clever marketing from DTS and an general misunderstanding of lossy compression (perceptual vs. reduced vs. entropy etc). Lots of studios only provide DTS because consumers think it's better and it'll sell more discs.

There's also the whole "preference" vs. "accuracy" debate, and it might be that DTS' performance characteristics are more inviting to the listener - a bit like some people preferring vinyl to CD - but when I compared DTS encodes to Dolby Digital and MLP (the latter being lossless), the DTS versions had very different waveforms and response curves to the other two.

If you made a DVD with DTS on it, you'd still have to include one of the mandatory formats - PCM or Dolby Digital - in addition, so once again your video data rate would take a hit to the tune of ~1.5Mb/s for no good reason.