Home Forums General Discussion SDI vs. Firewire Connection for Sony DSR 2000

This topic contains 6 replies, has 5 voices, and was last updated by  bockos 2 years, 3 months ago.

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    Dave Ireland

    I recently purchase a Sony DSR 2000 digital VTR. What are the advantages and disadvantages of connecting it to my GlobeCaster via Firewire or SDI? Which is better? Is there any difference in quality between the two methods of connection? I have the capability to connect it either way. Thanks!



    If it has RS-422 capability the only advantage I could see would be that Firewire would also take care of your audio inputs/outputs. This would leave more open channels in your actual audio board. As far as digital video quaility difference between Firewire and SDI, that’s a good question. Jim W.?


    Mike Haskell

    dv (firewire) is 5:1 compression. SDI can be uncompressed.



    Dave, if you have either option being even, definitely SDI. What goes in is what comes out.



    Depends on the DVI/O hardware codec that GS has decided to use. SDI also transcodes the DV signal. Now, there is an advantage to working outside the DV codec when editing. You loose those wonderful DV artifacts introduced when decompressing and recompressing your files when compositing. If this is a multi-layer one time pass video, DV is the way to go. If you introduce graphics in the pass you will see trouble. I have used an uncompressed version of FCP to edit with DV and it was truly wonderful to work with graphics. If you want to work with DV, buy a Mac and FCP for under $3,000.00 and then dump your work to the Trinity for finish.

    Mike: DV is not compressed again when you transfer the file to your DV workstation. The 5 to 1 you mentioned is only compressed in the camera or analog/SDI transcode to the DV deck.

    422 is said to be frame accurate while Firewire is said not to be (+-1-3 frames).

    Ted: I/O is dependent on the native format not the connection. SDI is not a native DV I/O. D9, Digibeta, D5 use SDI I/O, DV use IEEE for native I/O. Either way it is transcoded when using your GC or Trinity since neither GS product uses the DV codec when editing. The Toaster has a different way of handling the DV codec, but I am not educated well enough to debate it.

    The best codec is a software codec not hardware based.


    Although DV is said to be 5:1 compressed, if a true comparison is made with D1 it is not actually 5:1. This is because the sampling rates are either 4:1:1 or 4:2:0 which means that you start with 125Mbits/s instead of 160Mbits/s. 5:1 is therefore correct based on a starting bit rate of 125 Mbits/s but compared with D1 it is compressed by a factor of 6.4.



    Visit http://www.adamwilt.com if you really want to learn just about everything on digital formats. Be ready to spend the day reading:-)

    What does a 1394 connection do for me?
    Plenty of good things:

    * You can make digital dubs between two camcorders or VTRs using 1394 I/O, and the copy will be identical to the original.
    * You can do cuts-only linear editing over 1394, with no generation loss.
    * You can stick a 1394 board into your computer (PC or Mac), and transfer DV to and from your hard disk. If your system can support 3.6 MBytes/sec sustained data rate — simple enough with many A/V rated SCSI-2 drives and with most ATA/EIDE drives these days — the world of computer-based nonlinear editing is open to you without paying the quality price of heavy JPEG compression and its associated artifacts, or the monetary price of buying heavy-duty NLE hardware and banks of RAID-striped hard drives.

    You can do almost the same thing with a SMPTE 259M SDI (serial digital interface) transfer. But VTRs with SDI cost big money. 1394 is built into many low-end cameras and VTRs, and the connecting cable — even at Sony prices — is only US$50; you can find it for US$20 if you shop around.

    Also, transferring via 1394 is a digital copy, a data dump (as it is over the expensive SDTI interface on high-end DVCAM and D-7 VTRs). No decompression or recompression occurs. Transferring DV around as baseband video, even digitally over SDI, subjects it to the small but definite degradation of repeated decompression/recompression.

    If a digitally-perfect copy is a 10, and a point-the-camera-at-the-screen-and-pray transfer is a 1, here’s how DV picture quality holds up over different transfer methods:
    IEEE-1394, SDTI 10
    SDI 9.8
    Analog Component (Y, R-Y, B-Y) 9
    Y/C (“S-video”) 8
    Analog Composite 5
    Point camera at screen and pray 1

    Link to original http://www.adamwilt.com/DV-FAQ-tech.html#color_sampling

    Saved me a lot of time:-)

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