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Andreas Fernbrant November 27th, 2003 06:23 AM

Digital Video..
 
I have som questions for those who have experience with larger digital video camera like DigiBeta.

When you load you video in to the computer? is it done by FireWire? What format and compression do you get and edit with?
DV= DV Codec. But I can't see how that would fit to a Digi Beta?
Do you edit and render it as an uncompressed videofile?

DV is about 13-14 gigs per hour, what about digibeta?


/Andreas

Graeme Nattress November 27th, 2003 06:34 AM

DigiBeta uses a motionJpeg type codec at 50% compression. At those rates, it's practically lossless. It is generally connected to a computer NLE via SDI, and output via SDI. The SDI does not carry the "dub" signal (the compressed version of the video data) like with firewire, but a fully uncompressed 4:2:2 SMPTE 601 video stream, and hence is generally edited uncompressed.

SDI can carry the dub signal on other formats - BetaCamSX and (perhaps HDCAM will give access to the dub signal) because it can be used as a wrapper for any video data stream that fits within it's bandwidth.

Graeme

Jeff Donald November 27th, 2003 06:49 AM

SDI and FireWire are just pipelines. You can send whatever signal will fit within their bandwidths. Manufactures are adding FireWire compatibility to many of their new camera models. Transcoders are available to convert many different signals, using FireWire and SDI.

Graeme Nattress November 27th, 2003 07:07 AM

Yes - with boxes like the AJA IO, you can transmit uncompressed video over firewire - it has the bandwidth to cope.

Graeme

Jon Yurek November 30th, 2003 10:30 AM

Just to point something out though... even though you can transfer "uncompressed" video through a FireWire or SDI link, you're still getting only what you would have gotten if you had copied the DV or MJPEG stream directly and then converted to uncompressed 4:2:2 on your computer. Once it's compressed (as it is when it's stored to tape), you're not getting the information back that it threw away to compress it.

Speaking of which... if DigiBeta only compresses 50%, why not use something like the HuffYUV codec which is lossless and compresses around 2:1?

Rob Lohman December 2nd, 2003 06:05 PM

That's a good question Jon. Might have to do with bit allocation
and colorspaces. But then again I know everbody is using MJPEG,
it has been around for a long time.

Yes, we edit in DV. Our DV camera's encode directly to DV (25 mbps)
and this information gets transferred over the firewire in its
native compressed format.

So the capture is in fact just a "copy". On the computer we edit
this footage indeed with a DV "codec".

Dan Bohman December 24th, 2003 05:56 PM

clarify me....
 
does this mean there is no compression or decompression between the tape and the harddrive? i mean to say - when i capture into fcp4 via firewire from my gl2, is there no real codec being used? the appleDV codec that is used is really just for playback on the computer, right? is there a codec built into the camera for it to playback the digital tapes, or through the analog output? maybe i'm confused. hmm....

Glenn Chan December 24th, 2003 06:15 PM

The apple codec does 2 things: COmpress, and DECompress. When you are playing back DV footage on the timeline, it decompresses the DV footage into a format that plays on your monitor.

Suppose you add some effects to your footage. FCP decompresses the footage, applies the effects, then compresses the footage using the Apple DV codec.

Cameras/decks should have some sort of codec built in presumably (to play back and record DV).

Edward Troxel December 24th, 2003 09:59 PM

Quote:

does this mean there is no compression or decompression between the tape and the harddrive? i mean to say - when i capture into fcp4 via firewire from my gl2, is there no real codec being used?
This is TRUE. It is simply a file copy from the tape to the hard drive via a firewire connection. NO codec is involved in this process.

Ben Wiens December 25th, 2003 08:52 PM

DigiBeta
 
Graeme mentioned that "DigiBeta uses a motionJpeg type codec at 50% compression. At those rates, it's practically lossless". This must be 1/4 or less compression than MiniDV. Is this a major reason why big camera productions have so much better qualilty than those shot with MiniDV. Also is this the key big camera format or are there others?

Dan Bohman December 27th, 2003 10:28 AM

thanks for the help
 
i appreciate the answers everyone. definitely helped to clear up some questions. just one last semi-related question. all the talk about lossless editing, that not mini-dv is it? are they talking about larger format cameras? even older analog cameras at times?


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