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Jay Kelley
12-27-2003, 07:09 AM
I am using the new Panasonic AJ-SDX900 camera. It works on the DVCPRO50 Codec.
Normally I capture uncompressed SDI from the deck to the toaster in an uncompressed format. I do this to maximize the transfer.

My question is this: I am being told that a firewire capture from the deck to the DVCPRO50 codec on the machine is just as good as an uncompressed capture.

Is this true? If not why? Also don't I lose quality when taking the compressed footage into software like DFX+?

I will take this answer to others to enlighten them
Jay

johnq
12-27-2003, 10:49 AM
OK, something is confusing. You first say you are capturing in DVCPro50 CODEC (i.e., about 3.3 to 1 compression) and then you say you are using uncompressed SDI. Unless the SDX900 specifically has an output mode that is labeled "uncompressed," all the video from it is being compressed via its CODEC. My guess is that it doesn't offer uncompressed and the SDI connection is transferring compressed video. So the question of "analog" versus SDI versus Firewire is really about whose DVCPro50 CODEC is being used to uncompress the video. Analog out of the camera uses the Panasonic hardware CODEC; on the computer/VT3 side, who made the CODEC and how good is it?

I bet that you while you might use $50,000 of test equipment to measure the difference between the Panasonic and say Matrox or MainConcept DVCPro50 CODECs, you cannot see the difference...

John

UnCommonGrafx
12-27-2003, 02:33 PM
Yup JohnQ,
There's a lot of misunderstanding out there about this issue.

Jay,
Anytime it's a codec, it's compressed. No way around it. This is part of why the rtv format isn't used [able to be] with any other programs. That and the yuv... but I digress...

;)

If you capture to rtv, only manipulate it in VTEdit, then it will be in rtv format the whole way through. DFX can be told (and already does quite well right now) to work in the native format of yuv. DFX does quite well at not degenerating the rtv format in it's processing.

If you have a process you are following that is degenerating your material by a verifiable amount, by equipment, then bring the issue back here for the Aliens to go over.
It ought not be the case that you lose much quality using the tools discussed here.

Jay Kelley
12-27-2003, 02:41 PM
My post kind of sucked... Rushed through it and all....

The camera records onto it's tape using DVCPRO50 (3:1). Then I transfer that footage out via SDI to VT using the RTV CODEC.

HOWEVER... I am toying with the idea of capturing on the VT side using a DVCPRO50 codec as well. Basically I am getting a little cheap about my Hard Drives and space and all.

The folks at Panasonic are saying that as long as I am going from either SDI or Firewire DVCPRO50 camera to a DVCPRO50 Editing suite I should experience NO LOSS.

I always thought that every time you uncompress and recompress an image you lose a little. I'm not sure.

As for me... Right now I play it as safe as possible by going from Tape SDI to uncompressed on VT3. I think edit in VT3 (Which I hate but have no plug-ins for premiere Pro yet) do color correction in DFX+ and then output to tape or DVD or whatever.

Thanks for trying to help guys... Sorry for the bad post.

Jay

UnCommonGrafx
12-27-2003, 02:58 PM
Happy to, Jay,
Also, know that a firewire transfer and SDI are not compress/uncompress cycled transfers, i.e., they are the SAME as copying an MS Word file from floppy, to cd, to hd - No ONE ever speaks of losing quality in the file with all this copying. Same is true of a firewire transfer and SDI.
Going in RTV offers the most versatility in mangling the file with postproduction fun; it won't improve the imagery but it will lessen the hurt on it should you want to heavily process the footage.

IF you aren't processing the footage much, i.e., just a cuts or dissolves or dves type edit, then save on that space and go with the Panasonic AJ-SDX900 codec as it will have less 0/1 processing to go through.

I'm bored. Happy to help.

johnq
12-29-2003, 12:37 PM
Sorry there was some confusion on my part about SDI. I thought SDI was the same as Firewire/1394: a general serial protocol for any data. However, I found out it is not. I got the following from the Cypress Semiconductor web site about building a SMPTE 259 M SDI device:
"This standard [259M] documents the means by which SMPTE 125M or 244M bit-parallel (4:2:2 component or 4fsc composite) digital video is serialized, scrambled, encoded, and transmitted over a link." So the SDI video out of the AJ-SDX900 is not still in compressed DVPro50 format as I stated previously. But my guess is that its SDI is not true "uncompressed" video but "decompressed" DVPro50 video.

John