Newbie Question, Pulldown needed?

Posted: Tue Jul 29, 2003 4:29 pm

I've recently taken on my first film project and I am using my very low end home studio. I am doing this as a learning experience for myself. It is all DV and I was given the QT file as well as the wave files of the camera audio. The camera audio that I was given is slightly ahead of the video. I am assuming that I need to pulldown the sample rate from 48kHz to slow the audio by .1% because the transfer from camera was via firewire. The dilemma is that I am only using Sonar with a Delta 66 where I don't have the
options for SRs other than 44.1, 48.0, and so on. Anyway, assuming that I need to pulldown the audio to sync with the video, is there some clever way that I could do this with my limited equipment. Thank you in advance.

Posted: Wed Jul 30, 2003 12:55 am

Hey Erik,
I was able to remedy this by sending the audio from the DV tape at 48khz into my computer set at exactly 47.952khz. (I did this as D/A out and A/D in) Once the audio was re-captured into my computer, I changed my sample rate back to 48khz and it then changed the speed of the audio proportionally from what was 30fps to 29.97fps, thus slowing it down properly. This may be what you need to do. Not every type of device has the option of changing it's sample rate to 47.952 so you may need to find a digital mixer, A/D converter or the like that can interface between the incoming audio and your recording device. The MiniDV player and the recieving device cannot be linked together. They should only have the same black burst reference. I'm not sure if Sonar has anything other then 44.1 and 48khz, so another thing that you might want to varify is that Sonar is set to the same frame rate as the QT video. You should be able to varify Sonar in a preferences or setup menu in relation to video. (sorry I've vaigue but I don't use Sonar)
You can varify the QT's frame rate by opening it alone in Quick Time and goint to WINDOW-SHOW MOVIE INFO. (or ctrl-I) This will varify the movie's frame rate, size, length etc. I hope this helps. If not, please let me know and we can persue another approach!
Regards,
mIchAEl

Posted: Wed Jul 30, 2003 3:33 pm

Thank you very much for your response. Unfortunately, I don't presently have access to the original DV tape. I was only given the video without audio as a QT file (definetly 29.97 fps) and the audio as seperate wave files. Slowing my sample rate by .1% is not an available option with my converter. Since I will eventually be disposing the majority of the camera audio (though I'd like to maintain the usefulness of some of it), could I get away with using time expansion on the file? Would 100.001 as an expansion factor suffice (I am at work now and cannot experiment) or is my logic way off? I must say it is frusturating not to be able to have a continuosly variable sample rate and I can't imagine that it would be expensive for low end manufacturers to impliment this function (sorry for venting there). Thank you once again.

Posted: Thu Jul 31, 2003 11:00 pm

Hey, Ok, here's another idea!
I use Steinberg's Wavelab as an audio editor. First, open up your video's audio file in Wavelab and "select all", then go into the pull down menu called "process" and select "time stretch". (Or just push the "T" key on your keyboard for the shortcut.) You will then get a popup where you can change the exact length of your file by toggling the end time to match the exact length of your video. Hit "process" and voila!
To do this, you will have to do a couple of things first...
1- go buy Wavelab, or better yet, download a demo.
2-figure out EXACTLY how long your video is from the moment the audio is supposed to start and end. (If your video has timecode burn, you can just adjust the end by toggling the end in timecode, lucky!)
This is a crappy way to have to work but us indie people have to do crappy stuff sometimes!!
Let me know if this works!
Regards,
mIchAEl

Posted: Fri Aug 01, 2003 12:40 am

Awesome! Thank You!!!! I've been using Wavelab for a long time and it has saved me once again. Eventually, I will own the gear to do this properly but this has worked, or should I say... fudged it perfectly for the time being. I feel like this job needs duct tape or something to go along with it!

Posted: Sun Aug 03, 2003 4:55 pm

Great Stuff Michael! I am glad you are here.

--Rick

Respected Past Moderator Joined: Mar 13, 2001 Posts: 1256

Quote:

Originally posted by ErikSands:
I've recently taken on my first film project and I am using my very low end home studio. I am doing this as a learning experience for myself. It is all DV and I was given the QT file as well as the wave files of the camera audio. The camera audio that I was given is slightly ahead of the video. I am assuming that I need to pulldown the sample rate from 48kHz to slow the audio by .1% because the transfer from camera was via firewire. The dilemma is that I am only using Sonar with a Delta 66 where I don't have the
options for SRs other than 44.1, 48.0, and so on. Anyway, assuming that I need to pulldown the audio to sync with the video, is there some clever way that I could do this with my limited equipment. Thank you in advance.

First what EXACTLY do you mean by that the "camera audio" wave file is ahead.
Is it consistently ahead all the time the same amount? Or does it drift. If you slide it and sync it to picture at the start, does it gradually fall behind, or push ahead of picture? If so then the QT file and the audio files are at different sample rates.

Your Sonor session should be (I don't know sonor so I'm assuming it works @ 44.1 or 4 Cool

at 48Khz sampling frequency and a frame rate should be 29.97 frames. This is the standard for miniDV (and video). Import your WAVE file. ProTools will allow you to import the audio from different frame rates / sample rates. If do this and you ahve drift (and it sounds like maybe you have) then somehow the audio file was made wrong.
It can be corrected with soundhack.
http://www.soundhack.com/
get this software. Make a copy of theWAV audio file. Open the copied file after launching soundhack. After selecting the file, under "Sound-file" choose "Header". This will open up and let you adjust the section of the header (for the file in question) that tells the software how fast to play the sample. If it says 44.1 change it to 48, and visa versa. After you do this and save the file, and then import it into the session, the speed should be correct. Now you just need to sync it up and it should stay in sync.

Posted: Tue Aug 05, 2003 2:44 pm

Thank you for your response. Although I was already able to solve the problem with Wavelab (I'd of preffered to pulldown my SR, but not an option for me with my current setup).
As far as the camera audio, I meant the audio recorded onto the camera, not DAT. Apparently, the DV camera used doesn't recorded at a true 48kHz but .1% slower for its 29.97 frame rate. I wish I had the option for pulldown as one would have using PT. Unfortunately, I had to fudge it.

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