NLE (Non Linear Editing) on DVRs

vbimport

#1

NLE is common on computers with many authoring packages for creating DVDs. In my situation I can genenerate movie clips with titles,fades and transitions direct to my DVR and I want to do various cleanup edits there.

With the Frame Accurate capability of the Pioneer I can delete and insert sections/chapters accurate to the frame BUT at every Edit point there is a freeze when the title is played.

I have investigated this by recording to my Camcorder the output from a PC program which displays a frame count every 1/29.xx sec and transfering this on my DVR. Search for the Program GDOC under SPARKY and STUDIO 400 if you are interested. This title displays a consecutive frame count on every frame and so I can edit it and see how accurate the DVR is.

My results are as follows

After after a FRAME ACCURATE ERASE SECTION I can step through the title frame by frame and the cut is perfect… On the HDD I erased from (8 sec frame 1) to (12 sec frame 24) amd I step from (7 sec frame 29) to (8 sec frame 25). But when I play the movie there is about a one second freeze of the frame at (7 sec frame 29)

I copied this to DVD at High Speed and I got the same result …perfect cut ,freeze on play.

I then copied it to DVD in Real Time and the freeze itself was recorded. Stepping through frame by frame I got 34 frames of the (7sec frame 29) frame which shows the freeze was (1 sec 4 frames) long.

I appreciate that for normal TV commercial cuts this freeze can be managed by cutting at fades but it really makes the DVR unusable for any real NLE or even LE of clips.

What I don’t understand is why this occurs. The DVR obviously has a buffer between the read head and the output, and it can obviously fill it quickly give the EP capability, so why cannot it fill it in time to span a 4 second cut… surely the DVD/HDD has rotated many times in those four seconds so there should be no problem getting the next frame after the cut, and the decoding of that frame is no more than regular playback.

So I thought perhaps its a delay by the fact that I’m within a GOP and it take time to build it… so I repeated the test with a VM Compatible Edit at the I-frames and I still get the 34 frame freeze.

I had hoped that the Pioneer Copylist was going to address this since in theory it doesn’t need to do the copy in real time and I thought it might copy like a real recording with a pause at the start of the cut and a start record again when the frame following the cut was ready to display. Looks now like Copylist was a way for Pioneer not to have to implement Playlists on their HDD’s.

Given all this I have to conclude that DVR’s cannot be used for NLE or even Linear Editing… just sloppy editing.

But who can explain to me why it must be so? I think there is a huge potential for this. Surely this is not an omission in the DVD format standards? I was of the understanding that -RW(VR) was developed to address editing requirements,

PS: I also previously tried to use “Hide Chapters” on DVD +RW media and the freeze was still there although it appeared smaller. I did not have my GDOC tape at that point so I was unable to measure the + freeze.

I’ll post this to a number of DVR forums in hopes that some of you will share your expertise.

Thanks for taking the time!