DVL-Digest 598 - Postings: Index Cinema Products: anything goin Dubbing by Firewire from GY-DV FASTEST delivery to the US? - (2) - (3) - (4) Using a camcorder as pure data Using a camcorder as pure data-archive Cinema Products: anything goin - Adam Wilt Does anyone have any interesting news about Cinema Products, the folks who build Steadicams? A correspondent is having a heck of a time getting phone calls returned or product shipped; is CP undergoing some sort of difficulty, or is it just the summer slump? Cheers, AJW Dubbing by Firewire from GY-DV - Adam Wilt I was trying to dub a one-hour DV tape from my JVC GY-DV500 to my DV > editing deck, a Sony DHR-1000, using a Firewire cable. Everything was > going smoothly until about 30 minutes into the transfer, when both the > picture and the sound broke up (sound segments missing, video horribly > pixelated). I had to start over, this time putting the source tape into > a Sony VX1000. The entire transfer went just fine using the VX1000. I've had one occasion where a tape that failed progressively in a Canon XL1 and a JVC GR-DV1 played back fine in a DHR-1000 and a DCR-VX1000. Seems the Sonys do a very good job at reading marginal tapes (the best we can figure was that the Canon that recorded the tape got VERY hot in the summer sun, and the physical track pattern got distorted as the camera hotted up). What happens if you're just watching the DV500's analog outputs? Do they break up after the 1/2 hour mark, or is JVC playback out analog OK the whole way through? Cheers, Adam Wilt FASTEST delivery to the US? - "Perry" I thought Randy was talking about video files, probably for broadcast. 90MB gets you about 25seconds of DV! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ FASTEST delivery to the US? - "Perry" This is probably old hat, but it is the first time I've seen it: I've just been watching the BBC News and it included an item from Sierra Leone that was sent back via a 'Satellite Digital Phone Link'. The pictures were obviously heavily compressed, I suspect some form of MPEG, but they were quite watchable and a lot better than many others we've seen over the years from such circumstances. Anybody know any more about this technology? Perry Mitchell Video Facilities http://www.perrybits.co.uk/ FASTEST delivery to the US? - "Perry" This is probably old hat, but it is the first time I've seen it: I've just been watching the BBC News and it included an item from Sierra Leone that was sent back via a 'Satellite Digital Phone Link'. The pictures were obviously heavily compressed, I suspect some form of MPEG, but they were quite watchable and a lot better than many others we've seen over the years from such circumstances. Anybody know any more about this technology? Perry Mitchell Video Facilities http://www.perrybits.co.uk/ FASTEST delivery to the US? - "Perry" Elliot posted: >9600 bps max 7400 bit/sec typical A 30sec slot at 2mbit/sec (heavily compressed MPEG-2) will require 2 hours 15 minutes to send using a single phone.< Nah, this was worse than MPEG-1 in some respects (much heavier compression) although it did not appear to be pixel doubled. The item was at least 2 minutes long, so from your information I suspect the data rate was a lot less. Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Using a camcorder as pure data - Adam Wilt Actually because the machine does compression, this is what makes it > unacceptable for Data. Ah, but the data transferred over 1394 are *already* compressed, and the video/audio data is recorded bit-for-bit! Thus if you can format your data to fit in the video & audio sections of the datastream, and don't violate any of the rules in doing so, the data will survive, tape read/write errors aside. > The big question is "does the 'corder write the video to the > tape unmodified or does it compress it (or modify it in any way)?" Timecode is completely regenerated on consumer DV devices. Manufacturer-specific data & time/date info may also be regenerated. If you keep your data within the video & audio blocks, though, it should be OK. > Another one would be "can it cope with purely random data?". No. There are certain codes (like -MAXINT in the audio tracks, or 0 & 255 in the Y channel DC coefficients) that flag errors or are otherwise reserved with special meanings. There are also horizontal and vertical ECC / block-checksum codes that must be properly computed, and there may be other restrictions on the data I'm not aware of. So you'd have to at least make sure your data looked like legal, compressed audio / video data -- even if, upon playback, it has the appearance of properly-compressed noise! Cheers, Adam Wilt Using a camcorder as pure data-archive - Perry Mitchell Tim: I did a recent project that involved 13 source DV tapes, some audio CD material, several large graphic files and a pretty large final EditDV project file. After it was finally put to bed, it would have been nice to archive the whole project onto a single DV tape. Sure it would need some fancy processing to make the project fit all the new clip TC on the archive tape but it's not rocket science and DO already do something rather similar to enable a new Programme Log to be generated. Sure the non DV data would need some sort of rendering but I believe it would typically consume only a few frames of DV so it cannot take the time that Elliot surmises. To answer a couple of Tim's points: The data does not get put on the tape as it gets sent down the Firewire, it is shuffled around to minimise the effects of drop-outs and coding is used to get best efficiency and minimum errors. This is all transparent though and will be reversed without loss, there is no lossy compression applied at this stage. You could indeed simply use the video 'space' with a coded algorithm but this would be a lot less efficient. Several manufacturers have used this technique for back-up devices, and for years the industry standard for Audio CD mastering was based upon a standard U-Matic video recorder. Using a DV machine as a general purpose data recorder is surely a difficult proposition but it is certainly not as difficult as some folk would propose, and surely easier than the VHS and Hi-8 transports that are currently used. Using it to store a few frames worth of data alongside ordinary DV material is something that will surely come from somebody, why shouldn't it be you Tim? (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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