Using WP with Macintosh

[MovieStuff]

well again i'd like to point out that the subject of this thread is using a wp with a mac, and all i'm trying to do is suggest a solution to that problem. i've never said that recording frame numbers would in any way be better than a working on demand capturing.

The subject of this thread is, indeed, about using the WorkPrinters with a Mac. However, the thread (and its implications) was started back in November or so before the introduction of the CaptureMate software, which now makes on demand capture wtih the Mac viable at 6fps. I wasn't dissing your ideas. Rather, I was trying to bring you up to speed on what had changed since this thread was started, both in terms of new software that's available as well as letting you know the results of our own experiments. I didn't assume that YOU were suggesting time stamps would work better but WE certainly thought they would work better and were surprised to find that they didn't.

Actually I appreciate your input regarding suggested Mac interfaces because neither Jeff (DigVid) nor I are Mac users and the guy that wrote the CaptureMate software, while incredibly talented, isn't a WorkPrinter owner. Therefore, it's hard for me to get viable feedback unless a Mac/WorkPrinter owner invests in some software and let's me know how it works out. Understandably, it's hard to encourage someone that has ONLY a Mac to buy a WorkPrinter-XP knowing that, if a given software doesn't perform at 6fps, then the WorkPrinter becomes the world's most expensive paper weight since there is NO other Mac software available for rapid stop motion capture; Premier does rapid stop motion fine on a PC but not on a Mac.

Again, I wasn't rejecting your input but just trying to provide you with an overview of the dynamics involved, both technically and from a commercial viewpoint.

Roger

[digvid]

Matthias -

The last thing I want to do is to shoot down people's ideas...sorry if that's what I did!

- digvid

[blackfrog]

mattias wrote:

i think i could write a program to capture dv to disk while recording the frame numbers of the mouse clicks in about half an hour, if somebody is willing to write the software to extract the right frames.

Actually, with the current state of the union of QT and OS X, it is easier to extract the right frames than to guarantee 30fps dv capture on firewire. OS X is quite different from OS 9, and the QuickTime group is still working on capture optimizations. Because of this, applications like iMovie and Final Cut Pro don't use QuickTime to capture video, they use the lower-level Firewire API's. I've been warned by Apple Developer Services that these Firewire API's are subject to change, which means that any application using those API's will break with a future release of OS X. Of course, this is not a problem for Apple itself since Apple can coordinate iMovie and Final Cut Pro updates to match Firewire API changes.

This is why I am content (for now) to use iMovie to handle the real-time transfer of dv frames from the firewire bus. I can do this live with the camcorder on but not recording, or I can record to tape and import later.

Having said that, the upcoming Panther release of OS X is supposed to contain significant QuickTime performance enhancements. It will be interesting to see if traditional QT capture can guarantee 30fps firewire dv capture on medium and low-end macs.

As for extracting frames from a dv file, I think you will find sample code on the apple developer site to help you. Basically, you create a QuickTime movie from the dv file. Because QT can natively manipulate dv files, this is not a file translation, but instead creates a QT movie that references the dv file - very quick. Next, iterate the movie tracks until you find the video track. Next, call GetMediaSample() or something like that on the track, supplying the time you're interested in. This gives you a reference to a single dv frame. You can add that frame to a new movie, resulting in a QT movie that contains references to dv frames in the original dv file, but with the frames you want at the frame rate you want. Again, because you are manipulating references to dv frames, not dv frames themselves, this code should execute very quickly. Getting the time codes and time-bases right is probably the trickiest part. Again, there is sample code to manipulate QuickTime movies on the apple developer site.

cheers.

[Forever on DVD]

Hi everyone.

Roger and I once discussed the possibility of using a sound generator to output a signal with each cycle of the WP. There would only be sound while the frame was directly in the gate and the switch was triggered. This sound would be passed to the camera and recorded in sync of course with the video. Then you could search for only the first frame where the sound began and truncate all the frames following until the beginning of the next frame with sound. This way you wouldn't have to worry about any frame differencing and you could run the WP at pretty much any speed you like.

Any thoughts?

Shawn Kimmel
Forever on DVD
http://www.foreverondvd.com

[blackfrog]

Shawn wrote:

Roger and I once discussed the possibility of using a sound generator to output a signal with each cycle of the WP.

Interesting. Post-processing software would analyze the sound track, and keep each video frame that follows the start of the sound-wave, independent of the frame-rate.

I'd like to try that. Can you (or anyone) recommend a cheap signal generator with an external trigger? The Radio Shack web site wasn't too helpful. Since this is outside my domain of expertise, I've emailed an EE buddy of mine to see what he recommends. Shouldn't it be cheap to build one?

Cheers.

[Forever on DVD]

Can you (or anyone) recommend a cheap signal generator with an external trigger?Cheers.

Well, I'm so cheap (as Roger knows) that I'd probably just record a sine wave (using something like this: http://www.world-voices.com/software/nchtone.html ) to a portable tape recorder using the output from my soundcard. Then I'd play it back from the tape recorder while the WP runs and use the WP's micro switch to simply pass the audio along to the camcorder. I wouldn't turn the tape player on and off, just keep it playing and use the switch to close the circuit and allow the sound through to the camcorder. Wouldn't this work? Or, if you have another computer in the same room, you could simply use it to generate the sound.

I think Roger and Jeff have tried using sound and it didn't work well for some reason though. Maybe if they have a moment they can respond. I'd love to get my WP up to 15 or higher fps.

Shawn Kimmel
Forever on DVD
http://www.foreverondvd.com