Questions on sound in projects

[Doug2006]

If someone could set me straight on this I would appreciate it. I am making a training video and all shots are being captured with a sony analog 8mm camera. Which takes beautiful pictures but I will get a digital one for next project. All the footage is captured by a plextor 402 u with intervideo software. Only software I found that could do it without some problem. The plextor box makes mpeg 2 frame based files and the sound is mpeg2. So then I have edited these clips which is really cutting out unwanted stuff and adding titles which are color chips with typed in title. No special effects or filters. Here is my question All the files are in mpeg2 sound and I read somewhere that mpeg 2 is not dvd compliant. So why on earth is the plextor box putting this in mpeg 2 in the first place? And when do I convert it to dolby sound? I experimented with some clips and when I went to save them I clicked custom and put the dolby sound in there but then I have some clips that are dolby and some that are mpeg and when I put the whole thing together the dolby ones didn't sound as clear. So if I pick "same as project" when I go to save the completed clip then they are saved as mpeg 2. Then when I put them all together and "save render" the whole thing they end up still in mpeg2 sound. So what Happens in the "creat disk mode"? If mpeg2 sound is no good for a dvd then VS 10 must convert them to dolby at that time? I cant tell then because they just end up on a dvd and ts folders. So is there a problem with leaving this to the last operation or what? And when I go to the creat disc stage and import my save file it is a little confusing to me that it seems that there is another choice you can make there as to project conversion properties and a box opens up displaying what looks like what it is going to convert it to before it burns it. Mine always says 8000 and lower field first which is totaly not applicable to what I am doing. Is this really what its doing converting to what is in that box? The specs in the box do change the sound but how could it change the other stuff? As you can see I am not clear on what happens in this process. And I will put this in at the end, I did the other day think that possibly I may have found a setting in the intervideo software that would change the capture to dolby sound. It was in obscure place no one would ever think to look. I will have to experiment further but would i be better off to capture in dobly if I can? And is mpeg 2 sound good for anything?

[Ken Berry]

First, mpeg layer 2 audio is not part of the NTSC DVD standard, though it is for PAL. The NTSC DVD standard includes (L)PCM and Dolby audio. That being said, it is probably only older NTSC DVD players which might have difficulty with DVDs burned using mpeg audio. And indeed, a lot of people in NTSC countries no doubt regularly and successfully burn their DVDs using it. However, there are also quite a lot of people out there who have difficulty, in the form of out of sync audio, when they use it -- though it is by no means clear whether this is caused by using mpeg audio per se or because of some problem caused by extensive editing of mpeg-2 files more generally.

As you note, your Plextor captures direct to mpeg-2 and uses a hardware encoder to do so, which relieves the computer of the usual strain of capturing direct to mpeg-2. Since mpeg-2 is the required format for a video DVD, this saves a step, though the question of editing mpeg-2s does arise. Some people suggest that you use a specialised mpeg editor such as Womble. At the very least, I would suggest that if you intend to use Dolby audio in your final DVD, and you think you can capture using Dolby audio, then I would do so on the principle that the least changes to an mpeg-2 during the entire editing/authoring process, the better.

You are not completely clear about the exact steps you are taking, though I am assuming from what you say, that in fact you are following the recommended procedure of capturing, doing some (minimal) editing, then going to Share > Create Video File > DVD to produce the final DVD-compliant mpeg-2, which in a separate final step, you burn to disc using Share > Create Disc > DVD. It might seem counter-intuitive to take these separate steps when you are dealing with mpeg-2s all the way, but bitter experience on this Board suggests it is still probably a good idea.

There is another question at the Share > Create Video File stage, apart from whether you seek to change the audio to Dolby then or capture it in the first place, and that is whether to use Smart Render. With editing mpegs, any significant changes will necessitate a re-render of the file, and this will cause degradation of the video quality if it occurs several times. (How visible this degradation will be to the naked eye is another question.) In theory, using Smart Render will ensure that only those parts of the file which have actually been edited, get re-rendered, thus preserving the original quality of most of the file. But with earlier versions of VS, particularly VS8, there was a strong feeling that using Smart Render caused more problems than it solved, particularly in causing out of sync video and audio. So the recommendation was against using Smart Render. The jury remains out as to whether VS10 has solved those problems with Smart Render.

On a final point, I still have difficulty with the concept that your Plextor captures the video Frame Based. As you know, Frame Based is fine for videos which are only intended to be played back on a computer monitor but not on TV, or for slideshows made up of still photos. But it is likely to cause problems if producing a DVD destined to be displayed on a TV, which most DVDs are. The latter would require a Field Order of (normally) Upper Field First for originally analogue video (such as yours is) or Lower Field First for digital video (though obviously some devices use other methods in their hardware chip doing the capturing/conversion). If indeed the original capture is frame-based, then it (almost) beggars belief that you would eventually have to re-render the entire video to convert it to either Upper or Lower Field First, and thus potentially suffer a loss in video quality. However, I have never used a Plextor, and so cannot comment definitively. I'm quite willing to be howled down on this!!!

[DVDDoug]

So why on earth is the plextor box putting this in mpeg 2 in the first place?

So they don't have to pay a royalty to Dolby. They could have used LPCM, but it's not compressed... it takes more disk space. (My Hauppauge card does the same thing.)

...when I put the whole thing together the dolby ones didn't sound as clear.

Two things: First, there seems to be something wrong with the MPEG-2 audio to Dolby conversion. It seems that the level is too high, and this creates distortion. (I don't really understand how it's possible to screw-up a digital-to-digital conversion like that...) I cure it by setting the volume level to 75%.

Secondly, it is impossible to convert from one lossy compression format to another without some quality loss. There is quality-loss with each encode. With this set-up there are two lossy-encode steps.

SUGGESTION for Doug2006 - Next time, try writing in paragraphs. Your post was very hard to read, with all of those thoughts jumbled into one big mass. I'll bet most people didn't bother to read it!

[sjj1805]

One final point to add to the excellent responses by Ken and Doug.
Please read:
http://phpbb.ulead.com.tw/EN/viewtopic.php?t=27

[GeorgeW]

If you have no choice but to capture MPEG-1 Layer2 audio, then try to make sure it is the highest bitrate possible (that your capture software will allow -- assuming you will be converting it later).

As mentioned, if you are creating PAL DVD's, then just leave it as mpeg L2 audio. In fact, that's what the new HDV Camcorders use for audio.

If it's NTSC and for your own use, then if your dvd player will play it, just leave it asis. Otherwise, just convert it as the LAST step during authoring. For NTSC DVDs, hit that cogwheel icon (bottom left), and click the option to "Treat mpeg audio as non dvd compliant" -- make sure your project settings are using either LPCM or Dolby Digital audio, and burn (the former takes more space, so plan accordingly)...

Regards,
George