MPEG2 sound encode - PCM or MPEG2?

organism_seven wrote on 8/21/2002, 6:06 PM

Hi,

I am using VV 3.0c to edit all my DV footage, and I am then importing this into DVD Workshop 1.2 to produce the final MPEG2 files to write to DVD using the Pioneer A04.
I have given up trying to produce MPEG2 files in Vegas using the Mainconcept codec because despite enabling the "do not re-encode valid MPEG2 files" in DVD Workshop it still goes ahead and does it anyway!
So, I am just importing the native DV footage and letting DVD Workshop do the conversion. The picture quality is good (are they using the Mainconcept codec?), and it saves going through the whole process twice.

My question is this: I am using a Canon XM-1 which records sound in PCM. When I choose the settings to make an MPEG2 file, I have the choice of encoding the audio in either LPCM or MPEG2 audio.
Which option should I choose, and what are the differences between the two?
Also, on my microphone it states PCM. Is the LPCM option just the same thing?

Thanks for any advice you may have.

Comments

SeanC wrote on 8/21/2002, 8:29 PM

for what it's worth, I was a premier user, authored a few dvd's and learned a bit along the way.

PCM is an uncompressed format that can be the most pristine sound. Any MPG has gone through some form of lossy compression (it can still look and sound VERY good) and consequently has reduced file size.

either should work fine, PCM will sound slightly better, although it will make your burn longer. I *did* have a compatibility issue with a certain DVD set top player that would not play a DVD authored with MPG audio (we would get video, but no audio). I have read you may have higher compatibility if you do PCM audio, although I never tested to see if that would work.

I'm getting ready to do some dvd authoring with vv3 as my editor. Could some folks comment on the quality of the mpg encode compared to CCE or TMPG.

Sean

pelvis wrote on 8/21/2002, 9:56 PM

If you bump up the DVDWS encode rate to be bigger than the max of the MPEG source files, DVDSW will not re-encode the files (this is stated in Ulead docs, seems to work). So, if you use the default Vegas DVD render template and bump the DVDSW rate to say 8350, you should be cool, no re-encoding. Haven't tried a separate PCM- should be better in theory but the stock Vegas template gives decent results.

kkolbo wrote on 8/22/2002, 7:58 AM

PCM is the NTSC Standard for DVD audio. MPEG is not. MPEG audio is permitted in PAL DVD's. DVDWS 1.2 using the do not convert/re-encode valid files does not re-encode VV3 files on my system. You ,ay want to check your set up.

Unfortunately VV3 will not encode an MPEG-2 video with PCM audio, only MPEG. Bummer. Most newer set top players do not care, but the older ones will not play the audio.

I risk the older ones not playing it because I have found the MC/SF encode to be the best for the speed out there.

k

organism_seven wrote on 8/22/2002, 2:42 PM

Hi,

Thanks for the feedback.
I think I will stick with MPEG audio and risk the compatibility problems with older DVD players. I want the maximum amount of space available to fit the video footage on.

Thanks for the tip about bumping up the enconding settings in DVDWS to stop it re-encoding my footage. But I am still a little bit confused here.

If I use the standard template in Vegas to create my MPEG2 files the image quality is superb, but because of the file size it generates you can only just about fit an hours worth of video on to a 4.7GB disc.

As I understand it, you have to choose a lower bitrate to create a similar file size but which enables longer times to be used.
So what this means, in effect, is for every bit of extra time gained you have to sacrifice some image quality.Is that correct?

If variable bit rate is used, then this will compress to MPEG2 in a more "intelligent" way creating smaller file sizes, but still attempts to maintain image quality. Is this correct?

If the above is correct, is there a way for me to work out what bitrate to use for fitting different length of time movies on to a 4.7GB disc.
I know I have to leave room for add-ons such as menus etc, so I suppose we are talking about 4.3GBs of space.
So if I have a 1 hour,a 1.5 hour and a 2 hour movie which all need encoding to MPEG2, what is the best method to calculate the bitrate to use to ensure a file size is created about 4.3GB in size to ensure maximum image quality is maintained.

I feel as though I am asking questions that many others would want answering.
Are the answers to these problems available?
Can you guys help me?

Any help appreciated.

Regards
Organism Seven

blayzslayr wrote on 8/22/2002, 5:48 PM

I use a bitrate calculator found at vcdhelp.com. Also I found the the VV3 mpeg encoder is about a 3:1 time ratio (3 min to encode 1 min) and Tmpenc is about 16:1
time ratio but does give a better mpeg encode in my humble opinion.

JakeHannam wrote on 8/28/2002, 7:43 PM

Sonic Foundry needs to touch base with MainConcept (the makers of the MPEG encoder) and post an update here. Adobe Premiere 6.5 uses the MainConcept MPEG encoder and it renders audio to .WAV format which, as far as I know, is PCM.

If they won't do that, then maybe it is time to find another video app. In fact, what they really need to do is provide the ability to compress using AC3 for audio and then sell a DVD authoring program that supports AC3 (Dolby). If they did that, they would leave the rest of the under $1k world in the dust.

In the meantime, SF needs to get with MC and update the MPEC encoder to output PCM audio.

The_Jeff wrote on 8/28/2002, 8:48 PM

It is not all that hard to just render twice. Once where you render to MPEG but do
not include an audio stream and once where you render direct to a wav file. Then (assuming your authoring package supports it like DVD Complete and others do), just import the video and audio together.. It seems like more work but it sometimes saves time since the render goes somewhat faster (although the sum of the 2 renders is somewhat slower) but if you find you need to tweak the video or audio in some small way you end up saving a lot of time.

stepfour wrote on 8/28/2002, 10:00 PM

I've been using MPEG audio in all recent projects. Have delivered four DVD's that the customers have now played on many different players, and still no problems with the MPEG audio. The quality of the MPEG audio is very decent. Maybe, I have been lucky and no older players have been used, or, it could be that MPEG audio is more widely acceptable in DVD players than we realize. I'm going to keep using it.

Does anyone know if AC3 audio is far superior in quality to MPEG Layer II compression? I heard recently that the space requirements for the compression schemes are pretty similar, so, unless AC3 offers a great quality advantage, I will be very slow to spend a thousand bucks on it.

The_Jeff wrote on 8/28/2002, 10:21 PM

FYI My DVD Player (Toshiba 5109) does not accept MPEG Layer II compression.
Only does AC3, DTS, and PCM.

stepfour wrote on 8/28/2002, 11:02 PM

Way back when, when I started messing with VCD and SVCD, I remember it was Toshiba players (amongst others) that would not recognize the SVCD's. That had nothing to do with the audio but it came to mind when you mentioned your Toshiba doesn't play MPEG audio. Thanks for the info. It tells me that I might not always be able to rely on MPEG audio. How long have you had your Toshiba?

riredale wrote on 8/29/2002, 3:24 AM

The Dolby folks saw to it that the official DVD spec calls for either PCM audio or AC-3 in NTSC countries. It is apparent to me, however, that MP2 has become a defacto standard since DVD player manufacturers like to standardize on a single chipset the for world, so even though MP2 shouldn't work in NTSC countries, it usually does.

From what I hear, AC-3 is a little better in audio quality. I have always wondered why MP3 has not caught on in the DVD environment, since it has become a universal standard in audio players. MP3 is also a higher-quality compression method than its precursor, MP2. I think that hackers playing with novel compression formats like Divx use MP3 often.

vonhosen wrote on 8/29/2002, 10:22 AM

Organism_seven

If you want a simple way to work out what bitrate to use for your video do this

600/(minutes of video) = (bitrate for video & audio combined)

example
600/90mins = 6.6Mbs (for video & audio)

Now if you are using PCM audio (about 1600Kbs) then you will have avg 5Mbs for video
If you are using AC-3 or MPEG audio (@ 224Kbs) you could use avg 6.35Mbs for video.

Works for me.

The_Jeff wrote on 8/29/2002, 8:44 PM

I've had my 5109 for about 2 years. It was one of the first progressive scan DVD players. (You don't want to know what I paid for it!)

In any case, it also has marginal performace reading DVD+RW disks (some brands
work others done). Seems to read DVD+R disks fine and I have heard it reads -R (but not -RW) disks..

In any case, until some of the more recent models, it has been my experience that the cheaper players are more likely to be able to play disks with MPEG audio or mp3 based CD's.