DVL-Digest 1128 - Postings: Index Firewire & SDI Firewire & SDI - "Perry Mitchell" See my answers in [brackets] cheers Perry Mitchell Video Consultant http://www.perrybits.co.uk I'm doing some research, so I have several questions. Answers of any of these would be greatly appreciated. Why are there TWO different types of cables (Firewire and SDI) to transfer digital files between digital devices at high speeds and over short distances? [Firewire was developed as a general purpose digital transfer port by Apple Computer. It then got adopted by the DV consortia to use for transferring the compressed data. SDI was developed by Sony Broadcast to transfer uncompressed video data in a studio environment.] Is FireWire 1394 only for footage at 25 megabits/second, and SDI only for footage at 50 megabits/second? [Firewire (IEEE-1394) is under continuous development but current versions have a 'bandwidth' of 400Mb/s; DV video is actually nearer 30Mb/s when you include the audio etc. There is thus no technical reason why you couldn't use Firewire for higher formats. The original SDI is for uncompressed '601 video and 4 ch of digital audio, using 270Mb/s data rate. There are then several developments using the same physical ports to transfer compressed video such as DV50 and MPEG2 which are generically called SDTI. The system allows the compressed video to play at up to 4x normal speed. There are developments of SDI for HD use.] If FireWire is capable of higher speeds, is it just a case of SDI being the older format and high end digital decks having SDI more out of tradition than technical necessity? [Firewire itself was designed for a desktop environment and is limited to a cable length of 4.5m, although there are developments that can exceed this. SDI is designed for a professional broadcast studio environment and has a cable run capability of several hundred feet. It is designed to use standard video cable installations.] Related questions from someone who has only ever used FireWire: How does one capture DVC Pro 50 footage to edit in Final Cut Pro? What capture cards are available with SDI ports? [The obvious answer is Digital Voodoo, which captures SDI natively. The latest version of QuickTime supports the DVCPRO PAL codec directly, and FCP3 can apparently capture DVCPRO via Firewire, but this is of course DVCPRO25. I know of no plans to put compressed DVCPRO50 on Firewire] If DVC Pro 50 decks do have FireWire ports, won't they just dumb the signal down to 4:1:1 at 25 megabits/second? Isn't that I bad idea? [They don't! One day manufacturers might wake up to the idea of using Firewire and DV25 as a monitor port, in which case it would be much better than using composite video] Has anyone used the Miranda DV Bridge solution, which translates between SDI and FireWire? [there are several solutions but all are unfortunately expensive!] Thanks very much, Thomas Luehrsen [it's a pleasure!] (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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