How do I render a PCM?

MNJ wrote on 8/30/2003, 12:33 AM
This is probably a obvious thing to most of you, but it's something I can't find the answer to. I've seen many posts about PCM, but how do you render the audio to PCM? Up to now, I've been rendering the video of my short movies (about 15 minutes each) to DVD Architect NDSC Video, and then the audio to .ac3. I don't see a "PCM" format for the audio in the dropdown box. They work fine, but from what I understand the PCM audio will sound better and space is not a problem for my small movies. Can someone explain this to me. TIA

Comments

TheHappyFriar wrote on 8/30/2003, 12:37 AM
I belive PCM is a WAV compression format. So, if you render to just NTSC DVD and the audio out to PCM WAV< yo're all set.
farss wrote on 8/30/2003, 12:45 AM
The HappyFriar is correct as far as I know. .wav is PCM encoded.

Don't know why you don't like ac3, its capable of much better quality than .wav (at 16/48K) although there is more to fiddle with, I must admit I still haven't got it 100% to my liking but I'm getting closer.
MNJ wrote on 8/30/2003, 1:20 AM
Guys,

When I pick "DVD NTSC" template, it says

Audio: 224 Kbps, 48,000 Hz, Layer 2
Video: 29.97 fps, 720x480
Use this setting to create an MPEG-2 file with an NTSC DVD-compliant video stream, and an MPEG layer 2 audio stream.

I tried it and I get one file (a .mpg file). So, where is the PCM file or .wav file? I have to admit I'm still not getting it.

p@mast3rs wrote on 8/30/2003, 1:36 AM
You need to do two renders. For the video render as DVD Architect Mpg stream and then another render for your audio stream and then bring them both into DVDA.
MNJ wrote on 8/30/2003, 1:56 AM
Ok, I found the answer to my confusion. For some reason, I didn't see where it says

Save as type: Wave (Microsoft) (*.wav)

.....although I saw the other .wav (Scotts studio wav), which confused me for a bit. I was looking for a type of PCM or a file extension of *.pcm.

Does anyone remember a good source or post on this forum that compares the quality of ac3 vs pcm. Most of my videos are short, so size of the audio file isn't an issue. I just want to know which is better quality, with some technical explanation. TIA

farss wrote on 8/30/2003, 6:27 AM
If you're starting with wav audio and your videos are short I'd stick with PCM audio for your DVD.

The standard wave file is 16 bit 48KHz compared to 12bit 44.1Khz on a audio CD so its more quality than you need.

AC3 gives you huge dynamic range, higher resolution and better frequency response as it uses floating point numbers to represent the sound and yet fits it into a smaller sized file. But it has much more to configure to get right.

The defaults in VV seem to produce 'safe' ac3 encodes, you are unlikely to run into problems although you'll find your levels are down quite a bit. I've found that for most of my video by changing the dial normal value to -21 dB I can get a better level out of the player, but this setting depends on the dynamic range of your source.
roger_74 wrote on 8/30/2003, 9:53 AM
"Don't know why you don't like ac3, its capable of much better quality than .wav (at 16/48K)"

How can a lossy compression algorithm (AC-3) be much better than the same audio uncompressed??
farss wrote on 8/30/2003, 9:38 PM
Because it's compressed using a great deal of intelligence, this means it's capable of a far wider dynamic range, more than you'd want mostly.

Consider this, at 16 bit you've only got 2^16 possible levels to represent the signal, ac3 uses floating point numbers so it can represent a vastly wider range of values. Maybe you want the sound of leaves rustling at an SPL of 20 dB on a rear channel and an explosion at 110 dB on the front channel, ac3 can cope with that. The encoders also let you produce soundtracks fo different environments, what you can safely play in a cinema with huge dynamic range you wouldn't want on a DVD for home viewing.

I don't think though its designed as a general recording format, so the fact that its lossy is of no consequence, once its encoded the losses don't matter but if you kept going through the encode / decode process you'd certainly hit problems.

However from what I can work out you do need to know what you're doing with it, the papers from Dolby take a lot of reading, I have seen a summary of it some where on the web.