MPEG audio vs LPCM

TDK1044 · Post by **TDK1044** » Tue May 23, 2006 11:29 am

I capture my DVD quality footage using the excellent ADS DVD Xpress DX2 capture device. Regarding my audio capture, I can either use MPEG audio (224kbps) or LPCM uncompressed audio. The audio is great using either setting and there are no dropped frames using the LPCM setting. Having tested some renders and burns within VS10, using the default DVD NTSC settings in VS10, there doesn't seem to be an audio sync problem rendering a file captured using MPEG audio and then creating one with LPCM audio so that my burn properties will be the same as my rendered file. As my initial captured file is obviously much smaller using the MPEG audio setting, can anyone see a problem capturing using MPEG audio and then rendering and burning using LPCM? I know that standard procedure would be to capture, render and burn using identical properties, but VS10 seems fine with changing from MPEG to LPCM.

GeorgeW · Post by **GeorgeW** » Tue May 23, 2006 11:39 am

It will depend on how important your audio track is. When you compress to mpeg (on original capture), you are throwing out some details to achieve the mpeg compression. This isn't too bad for everyday stuff (birthday party, kids sporting event, etc...).

Some of the USB2 ADS Tech mpeg-capture devices can capture Dolby Digital audio -- check if yours can (probably not, but might be worth a shot to have a look...)

Regards,
George

p.s. as you noticed, mpeg audio (vs. lpcm audio) leaves more space for your video. OK for PAL, not as good to be compatible with all NTSC DVD players. Dolby Digital audio is your best bet for compatability and space usage.

TDK1044 · Post by **TDK1044** » Tue May 23, 2006 11:51 am

Thanks for your input, George. I use Video Studio as a hobby. Mostly, I use it for making wedding videos for friends and family. Most of my audio is therefore a mix of dialogue captured using a radio mic at the ceremony and music played through a speaker system at the reception. I really couldn't hear a difference in the MPEG audio to the LPCM audio, but I'm no audio expert like some of you guys. Thanks again.

Post by **Ken Berry** » Tue May 23, 2006 10:24 pm

To repeat George's comment another way, mpeg layer 2 audio is a compressed format. (L)PCM is not. To me, it does not make sense to capture using mpeg audio then later transcode it to LPCM since you cannot improve the quality of the original audio by doing so (just as you can't improve the quality of mpeg-2 video by transcoding it to DV/AVI). Since LPCM does, however, create much larger files, it would make more sense to capture to LPCM and later transcode to mpeg audio if space becomes an issue, or else leave it as LPCM throughout if space is not an issue. Or if you know in advance space will be an issue, then capture in mpeg audio as you are now (or preferably Dolby if your capture device allows it) and leave it at that. Or yet another option -- capture mpeg audio then output to Dolby.

Dolby could be preferable since, as George also indicated, mpeg audio is not part of the NTSC DVD standard, though (apparently -- I live in a PAL country) most NTSC DVD players these days can play it. But this is a factor to bear in mind if, for instance, some of your DVDs are going to be played in older DVD players which may not have been made to play mpeg audio...

TDK1044 · Post by **TDK1044** » Wed May 24, 2006 12:55 pm

Hi Ken,

I totally get the point you're making, but in reality, I make a lot of wegging videos which are abot 70 percent dialogue and 30 percent the other stuff that happens at the reception. I therefore use MPEG audio at capture, but because I'm adding .wav audio files ripped from my CD for music montages etc, I render my projects and burn at LPCM to keep the quality of the music and added audio layers high. I don't really see the point in using LPCM to capture ceremony dialogue/speech when I really can't hear the difference between MPEG and LPCM when it's just speech.

Trevor Andrew · Post by **Trevor Andrew** » Wed May 24, 2006 4:09 pm

Hi

If you are in the US then capture LPCM rather than Mpeg.

If I have the option to capture Digital Dolby then I would use that.

If I hire or buy a DVD Video it is most likely to be Digital Dolby Audio.

If Mpeg/LPCM is your only option then stay with the one you captured.

Trevor

TDK1044 · Post by **TDK1044** » Thu May 25, 2006 12:41 pm

Thanks, Guys. What works best for me is capturing, rendering and burning using LPCM. File sizes are large but I have pleanty of room. The end result is very good. Thanks for all your input, it's much appreciated.

Mike-Mat · Post by **Mike-Mat** » Thu May 25, 2006 5:47 pm

If you capture Mpg audio and re-render it (or re-process it in some way) multiple times. the quality will degrade. If you do a capture and then just cut and burn. you wont see much difference.

If you do a 196 Kbs mpg capture it's pulling out small sections of the audio to make is smaller. Re-processing again with the same setting will do the same. It pulls out small sections of an audio that already has "holes" in it. Now it starts to sound choppy.

I dont think that will matter for your wedding videos. But that's what's happening. I make training videos. So I record at LPCM to get the best quality for the initial sample and then in the final mix I output to mpg 196kbps. It's the lease I can do for people who have to listen to my voice for any length of time

Mike