Comments

farss wrote on 12/10/2004, 12:16 PM
This is not anything new, I've mentioned this in several posts over the last few weeks.
In summary. HDV uses a 15 frame GOP. Each frame apart from the first I frame in a GOP relies upon the previous to rebuild the current frame. Worst case therefore a damaged I frame will result in the loss of 15 frames which equates to 0.5 seconds of NTSC, a bit more for PAL.
Mpeg-2 is more error tolerant than DV25 upto a point. It has more error correction but obviously once the error exceeds the limit of the correction algorithm then a larger amount of data is lost than would be the case for DV25. To highlight the point, it's quite unlikely not to have a single dropout within a DV25 tape, mostly they go unnoticed.
Using good tape with HDV you'll get no dropouts, a big plus over DV25. Using poor tape or switching tape formulations you definately risk having a serious dropout in both DV25 and HDV except with HDV the impact will be much worse.
So I guess the choice is this, shoot HDV with common sense and have no glitches at all or shoot DV25 and put up with the odd glitch. Of course if you're one of those guys who think tape is expensive why are you shooting HiDef, buy a cheap camera and spend the money saved on decent stock.
Bob.
Barry_Green wrote on 12/10/2004, 5:17 PM
This isn't new, we've been talking about it. I've seen it happen, and it is absolutely disturbing -- if you get hit with a dropout, it'll freeze the video for a half a second.

The thing is, it appears that any dropout of any type causes the camera to drop an entire 15-frame group. So where in DV25 you might get a little tiny dropout that affects maybe 50 pixels scattered across the frame, in HDV you'll have a 15-frame lockup. If you've ever seen your NLE drop a frame on playback, think of what it would look like if you dropped 15 frames in a row -- that's what HDV does.

And whereas DV dropouts can be fixed/masked in post, there's no way to recover from a half-second freeze-up! You'd better hope you have something to cut away to.

I do believe Sony knew about this, and that's why they introduced a new tape. Whatever you do, if you use HDV, use the absolute very best tape you can. And I think something like a Firestore would be MANDATORY if you're shooting irreplaceable footage (like a wedding or whatever)... hopefully FireStore will release an HDV-compatible model soon.
farss wrote on 12/10/2004, 5:25 PM
In all fairness to Sony this isn't an issue of their making, they built the camera to the HDV specs and that's where the issue starts, with the recording system. Certainly the Z1 recording in DVCAM mode should have less of an issue with this problem.
At the same time I really wonder if this type of camera is the ideal for one shot events anyway. It seems to me to get the best out of HiDef you need to do a bit of work getting the shot right to start with and that seems at odds with those ty[e of events. Perhaps the answer there is to use it to shoot DV25 and keep the HDV stuff for things where you've got more time and you'll probably have more than one take anyway.
Then again yesterday I watched about an hour of footage shot on the camera with vanilla Sony MinDV stock and not a single problem with dropouts, much more than I can say for how the camera was used though.

Bob.
Spot|DSE wrote on 12/10/2004, 9:27 PM
This is why Sony developed the new tape. It's more robust, and more steady. I shot for the past 3 days with the Z1, nary a dropout anywhere on stock DV Tape, but I'll still be using the 18.00 tape when my Z1 arrives.
Xander wrote on 12/10/2004, 10:40 PM
That is why they have a 3db better carrier to noise ratio compared to Sony DV tapes.
SimonW wrote on 12/11/2004, 11:01 AM
I pity the person who videos a wedding and suffers from a dropout like this.
farss wrote on 12/11/2004, 1:37 PM
Believe me I've tried to help people who've had much worse things happen than that! How about having the minipin plug come out just a little bit pretty well killing all audio, grab you for an issue. By some miracle there was just a smidgen of audio still there at about -30dB and full of buzz, many hours in SF retrieved something that was barely useable.
Bob.
Barry_Green wrote on 12/12/2004, 3:50 PM
As Bob said, this has nothing to do with the Sony in particular, it's going to be endemic to all HDV recording systems.

The Sony probably shows it more than the JVC because the Sony uses longer GOP's, which mean the duration of the dropout is longer on the Sony.

"Certainly the Z1 recording in DVCAM mode should have less of an issue with this problem."

In DVCAM mode there will be less dropout, but there will be NO HD. People keep talking about it like as if there will be some lesser-dropout issue on the Z1, and that's just not true. The Z1 doesn't record high-def content in DVCAM mode, it records DV content in DVCAM mode. For HDV content you record in HDV mode, and that mode will be identical to the FX1. There's no such thing as HDVCAM as far as I know, and that is what I think people are thinking the Z1 will have. It won't. It'll have exactly the same dropout issues as the FX1 (or any HDV product).
farss wrote on 12/12/2004, 7:45 PM
That's kinf of disappointing, we were sure under the misaprehension the the Z1 would write HDV but using DVCAM write speed and track width, there's no technical reason why this couldn't be done that I can think of as the data stream is the same in DV and DVCAM.
Bob.