ac3 or lpcm

[humbleboy]

Hello,
I am a noob and I read in one of the guides that it is better to use ac3 instead of lpcm.
after I encode my dv into mpeg2 , I extract audio from mpeg2 and convert to ac3 then I load ac3 an replace current audio in tmpgenc dvd author.
But I can't seem to notice a difference in audio when played on DVD!!!.
Is what I am doing is correct?

I am trying to get to best result for my audio as most of my footage is concerts for kids.

Thanks for any help.

[gshelley61]

AC3 is not better. Just much smaller file size than LPCM. Saves space so a higher video encoding bitrate can be used (higher quality).

[mats.hogberg]

As AC3 is a compressed format, LPCM should be better, when we talk about audio quality. The downside is that it takes like 10 times the space on disc.

/Mats

[NamPla]

Ha, as far as I'm concerned (aka AFAIK) there's no difference, only ac3 takes up less space! Ac3 sounds great, tho' I admit I don't have the foggiest what's the difference between these computer "formats"! (I'm no programmer). Somehow a few people in this strange world have the ability to "compress" audio (and video) without losing information. THAT, I find, is quite remarkable! Cheers to them!

[mats.hogberg]

Somehow a few people in this strange world have the ability to "compress" audio (and video) without losing information

...but the people behind AC3 are not among these few. That said, given enough bitrate, neither can I distinguish between AC3 and LPCM audio.

/Mats

[dcouchotvore]

I like AC3 just because it takes up less space, figuring that leaves room for a higher bit rate on the audio. No difference to my ear either. I also know that AC3 supports 5.1 audio, which I rarely use. LPCM might too. Don't know.

[bezhan_o]

ac3 doesn't work for me. My dvd's come out audioless. someone help me please

[humbleboy]

Thanks all for the info
When replacing my audio with ac3 in tmpgenc dvd author i don’t seem to gain more space. I have an mpeg2 file 4.4 gb I extracted audio, converted and imported as ac3 which is about 100 mb but still shows file size can not fit, I thought i should gain about 1 gb of more space !
any help please
thanks you

[guns1inger]

Is your video a program stream (audio and video combined) or elementary stream (video in one file, audio in another) ? If it is elementary, have you only loaded one audio track (the AC3) ?

[humbleboy]

If i understood this well my video should be a program stream because both video and audio are combined in 1 mpeg2 file and loaded. but when i am importing my ac3 it seems that it not replacing the original audio !

[offline]

On good equipment LCPM does sound better than AC3 but if the source audio file you are using is less
than CD quality it does not make a noticable difference.

[Red96TA]

One word worth noting is that ntsc players are standardized toward ac3 while pal players are standardized toward pcm audio. On my commercial discs authored with ac3, I have YET to get any returns due to audio problems. I get about 5% returns with my commercial discs that used pcm audio.

[midnightsun]

ac-3 is PAL standard. Where did you read that info??

[cellmaniac]

Did you install the ac3 plugin for TMEGENC? Also, I believe the plugin only is suitable for 2 channel ac3. I've only had success using DVD Maestro to author the DVD with elementary m2v video and ac3 audio files.

[Red96TA]

midnightsun, I read the info here...maybe Lordsmurf told me that nearly a year ago. Maybe he was wrong.

cellmaniac, I use Vegas5 to do all my audio. It lets me decide between 2ch through 5.1ch ac3 encoding...then I drop everything into dvd-lab.

[mattyboy]

When I was using tmegenc dvd author, I chose linear PCM instead of ac3 because my HT reciever can handle it, plus I have my soundblaster card set to NOT use its DD decoder so its in pass thorough mode, it goes right the the reciever, but once I finished and burned the movie to a dvd, when I was playing it in my dvd rom drive, the sound was a mess. Just fizzing and crackling plus I got the message on my reciever that says "OVERFLOW". That happens basically when theres to much being fed to it. I wish I knew what I did wrong when encodong the movie. (it was a AVI to dvd transfer)

[offline]

Red96TA,

PAL and NTSC have always had AC3 and LCPM as
part of the DVD standard. It is MPEG 2 audio that is
supported by more PAL players than NTSC.

[humbleboy]

I noticed that when encoding my dv to mpeg2 using powerdirector 3 i am getting "MPEG-1 Audio Layer-2, 48000 Hz Stereo, 224 Kbps"
Is this a good audio quality ? I can hear a slight difference from the original audio recorded but not that bad, so I wonder if i should encode audio into other format , or shall i increase to more that 224 Kbps to have best quality !

[mats.hogberg]

The more kbps the better, yes. But I have a feeling (please correct me if I'm wrong!) that AC3 is more efficient (=providing a better audio quality at the same bitrate) than mp2.

/Mats

[guns1inger]

mpeg-1 audio layer 2 was made part of the DVD spec for european players to appease certain manufacturers and distibuters. As Australia also uses the PAL standard, we have inherited compatability by default. The standard has two major flaws. It is not as good a quality as AC3 at the same bitrates, and while it purports to contain 7.1 channels, there are only two discrete channels, and a third channel of surround information. Think of it as a slightly more sophisticated version of ProLogic II, but only for specifically encoded sources (as opposed to PLII, which can matrix any stereo source).

[jimmalenko]

PAL and NTSC have always had AC3 and LCPM as part of the DVD standard. It is MPEG 2 audio that is supported by more PAL players than NTSC.

That's what I thought

[humbleboy]

but back to the main issue i still can not replace audio by ac3 in tmpgenc dvd author, anyway to mute mpeg2 so the size will be smaller and then use ac3 audio instaed ?

[mats.hogberg]

I'd demux the m2v stream out of the mpeg, use m2v as video source (or why not encode the DV to m2v only, to begin with?), AC3 as audio source. But I think there should be an option to use "external" audio as a replacement for the "original" audio, not as a 2nd audio stream...
OTOH, TDA is geared towards ease of use, not fancy features, so this feature might be overlooked.

/Mats

[hiptune]

One word worth noting is that ntsc players are standardized toward ac3 while pal players are standardized toward pcm audio. On my commercial discs authored with ac3, I have YET to get any returns due to audio problems. I get about 5% returns with my commercial discs that used pcm audio.

I've read this comment of your a few times now. And I finally decided to ask....

What kinds of commercial discs have you gotten 5% returns on due to LPCM audio? And what Authoring program do you use.

I am a producer of various video material on DVDs. And I stick to LPCM for anything 69 minutes or under. And ac3 for the longer running times. Never has a sound issue with any disc ever. And most of my discs are 55 minutes average. There is always a first I guess. But I would like to hear more about your 5% duds.

[Red96TA]

hiptune,

I assemble my clips in Vegas5 and frameserve them out to Mainconcept (elementary video and audio(lpcm). Once that's all done, it all gets put together in DVD-Lab. That 5% usually have comments like, "I tried your dvd and the video works great, but there's no audio." After trying for a while to see what kind of sound system they have on their television, they usually give up and ask for a refund.

All of my newer dvd's have ac3 all the way around and I have yet to get one return.

I digress on the 5% statement...of the ~800 dvd's sold last year, I've had about half a dozen returned because the audio didn't want to work on their system for whatever reason. Half a dozen of 800 is what.... 0.0075%...not even 1% in retrospect, but I suppose I remember the lost $$ more than the percentage.