Timing issue with different programs.

[Jon.G]

I apologize if the title doesn't best fit this.

Ok, I have a hobby in which I author hybrid dvd-audio / dvd-video discs that contain quadraphonic albums converted from analog sources, so that they can be played back on home theater surround systems, in dvd-audio with high resolution 24bit 96kHz audio for those with dvd-a playback, and in either dts 9624 or dolby digital on dvd-v for those that don't have dvd-a playback.

Recently, I found out that my testing has not been thorough enough, and that my chapters that I've set to skip to songs aren't lining up properly on the dvd-v portion.

Here is the procedure I go through once I have my audio recorded in and tweaked, and slides made up for each song:

I encode the audio to 3 streams, MLP for dvd-a, dts9624, and dolby digital/ac3.

In Magix Movie Edit Pro 15, I lay out the audio files as a guide (I usually use a set of 4 files that have been downsampled to 16bit 48kHz, which I use for ac3 encoding). I then line up my .bmp slides on a track, and line them up to the start of each song, and notate the time that each song starts. For simplicity, I try to pick a spot of silence before the next song starts that lands on an even second, so I don't have to deal with a frame or decimal issue, a second is a second after all (so I thought). Once laid out, I have a slideshow that is the exact same length as my audio, I remove the audio tracks, and export to mpeg-2 with no audio. (I have gone back and done this same process with vegas, and vegas has given me the same results as magix in this situation)

I author the dvd-a portion in discWelder Chrome. I import my MLP, set the tracks using the timings I wrote down from Magix, setup my menu.

Then, in dvd lab pro 2, I import the dts and ac3 audio streams, and the slideshow mpeg. I put them into a movie, setup to have alternate audio tracks to the same mpeg. I set menus that allow the user to select the audio stream, and then a track menu. I compile.

Back in chrome, I import the video_ts folder. I burn to a disc.



What I have found from this process is that I end up with a disc that is perfect on the dvd-a portion, the chapter times I notated in magix works perfectly on the dvd-a portion. However, on the dvd-v portion, the chapters start out fine (which is why I never detected it, skip to a few tracks, good, ready to go, and I mostly listen to the dvd-a portion myself). However, as the disc continues, the chapters get late. For example, I have found that on the latest disc I tried to author, the last track starts 3 seconds into the song.

I have found the following. Lets use the last track of the latest disc to explain what the different programs "see".

When the audio is laid out in magix and vegas, the last track starts at 00:56:08:00. Using this time to set the chapter in chrome works.

However, when I open the original audio in sound forge, the song starts at 00:56:05:00. The mpeg-2 that was created in magix (and vegas) show the slide change that was timed for 00:56:08:00 actually happen at 00:56:05:00, which lines up with the audio fine. I also notice the mpeg-2 files I exported from magix and vegas are 3 seconds shorter than my audio files.


Are there 2 different definitions of a second? I thought that a second is a second. I mean, you take a stop watch, let it tick, there's a second....why screw with that? Where did my 3 seconds go? The audio doesn't sound pitched when comparing the dvd-v to the dvd-a, yet the timings say one is 3 seconds longer than the other.

Can anyone explain what is going on here, and what I should be doing to get all my files to be the exact same length, with the same timing, so I can use the same chapter layouts for everything?

[manono]

You're checking the timings using 2 different methods. One (the one that says 56:08) is using drop-frame timing (29.97fps), and the other (56:05, accurate for the audio but not for the video) is using non-drop-frame timing (30fps). You're already aware of the problem and how to fix it, so adjust the chapter points accordingly. I don't use any of the programs mentioned, so I can't help there.

I also notice the mpeg-2 files I exported from magix and vegas are 3 seconds shorter than my audio files.

Another mistake, if the intent was to make the video the same length as the audio, and probably for the same reason.