AC3 or not AC3, that's my question!

[moviebuff2]

Hi everyone:

I transfered a laserdisc to DVD, using the Philips DVD Recorder. The audio part was orginally digitally recorded in stereo, and encoded in AC3 by the Philips.

The original digital audio of the laserdisc was bad. It was full of noise that sounded like something scratching and which grew loud with the music. Naturally, the AC3 audio inherited all of those annoying sounds.

I demuxed the AC3 audio then used my audio cleaning software to get rid of most of the annoying sound while leaving the piano sound virtually untouched. After the clean up, I saved the audio as wave.

Last, I used TMPGEnc DVD Author 1.6 to load the DVD. But for the audio part, I replaced the noisy AC3 with the wave file. Then I burnt a DVD.

In play back, I noticed on my AV Receiver that the audio of the new DVD was no longer AC3. It's only stereo.

My question is: does it really matter that the new audio is only in stereo and not AC3 stereo? After all, everything was done digitally, from the noisy AC3 to wave to simple stereo in the DVD.

[guns1inger]

The only issue with going to wav is the space it requires. A stereo AC3 file can use a bitrate as low as 192 kbps and still sound OK, and from a good source, you still don't need to go much above 256 kbps for 2 channels. For an LPCM wav file, your bitrate is 1536 kbps. On a short film you may not notice it, but on a longer film, you take a huge bitrate hit on the video to accommodate.

[Baldrick]

No, wav/pcm stereo = ac3 stereo. See http://www.digitalfaq.com/dvdguides/authorburn/intro.htm#audio

[jman98]

In play back, I noticed on my AV Receiver that the audio of the new DVD was no longer AC3. It's only stereo.

My question is: does it really matter that the new audio is only in stereo and not AC3 stereo? After all, everything was done digitally, from the noisy AC3 to wave to simple stereo in the DVD.

It's normal that your audio is only stereo now. I think that DVD video doesn't support multichannel PCM/WAV files, only stereo. DVD Audio does support multichannel PCM, but I've never seen a multichannel PCM file on a normal DVD video disc.

There's nothing wrong with PCM/WAV audio. In fact, I have recorded a few laserdiscs to DVD myself and none of them have AC3 audio. I use a video capture card on my PC and I have no way to record AC3 audio in, so my audio is always recorded in MPEG-1 layer II stereo, which I then convert to something else, usually AC3. In a few rare occasions for very short laserdiscs (less than 60 minutes) I have converted the audio from MPEG-1 layer II to PCM because even with very high video bit rates, I still had enough space on the DVD for PCM audio, so I just used that. So don't worry about what you did. It's fine.

[moviebuff2]

Thanks, guys.