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DV--PC; "Capture" or file transfer? Why no hi speed?

Discussion in 'Digital camcorders' started by Panuraj, Feb 8, 2005.

  1. Panuraj

    Panuraj Member

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    I'm using a Sony DV and Roxio to "capture" over a firewire.

    1.) Am I really "capturing" or am I lifting and upload the exact sequence of bits from the tape "file?"

    2.) Must I upload my DV tape file at playback speed? I'm an old computer guy who remembers backing up and restoring huge disk file systems to and from digital tapes (DATs)at high speed. Is there some way I can do a high-speed upload from the Camcorder or the tape without having to watch the actual content in real clock time? I want to upload a 60 minute tape in much less time than 60 minutes. Is that possible? How?

    Thanks.

     
  2. TPFKAS

    TPFKAS Regular member

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    1. Yes, you are uploading the exact sequence of bits if your are using Firewire. This why it is referred to as "transferring" rather than "capturing". See also http://www.digitalvideoclub.com/basics/transfer.php

    2. Technically speaking it should be possible. The data transfer rate of Firewire is sufficient to transfer at higher playback speeds. However, I have not seen programs that have this option.
     
    Last edited: Feb 8, 2005
  3. Panuraj

    Panuraj Member

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    Thanks.

    When doing my first transfer after getting the fire wire, Roxio quickly scanned the tape looking for scene boundaries. I formed the opinion then that it was transferring at that speed, but was quickly disappointed to learn it was just sniffing the tape for scene boundary marks.

    Clearly both the software and the Sony can push bits through the firewire much more quickly than at playback speed. Its depressing to think that neither Sony nor Roxio could imagine that users would want to make the exact transfer as quickly as possible.

    I can understand that video "capture" must take place at the video frame rate, but a tape transfer is not a frame by frame video capture. The software is simply reading the tape and co-incidentally displaying the output.

    I have a number of archived tapes that I'd like to upload, edit, and re-archive on DVD media. Its kind of a bummer to think that for every hour of DV tape, it will take me at least an hour to upload and re-archive the content.
     
  4. TPFKAS

    TPFKAS Regular member

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    The fact that you were able to scan the tape at high speed does not mean that you can transfer at higher than playback speeds. For example a program like scenalyzer can create a preview video file while scanning at higher speeds, but it does that by skipping frames.
    You should also know realize that, although the Firewire alllows higher transfer speeds there may be other limiting factors:
    - The maximum speed that the camcorder head can scan the tape with the required accuracy.
    - The maximum speed the PC can wrap the video in an AVI-file. See http://www.digitalvideoclub.com/techinfo/avi.php
    - The maximum speed data can be written to the hard drive.
    I did not really study the subject but I assume that the first one is the most important limitation. I personally use Premiere for transfer and when I use dvice control to play at high speed I see blocks appearing in the image pointing at a problem in accurate frame reading. With all these system dependent limitations I can see the point that program developers don't wnat to incorporate it in their programs.
    Luckily, once you have started the transfer you can just go do something else (spend some time with friends ;-) ). And think about the time you are loosing to encode it to MPEG-2 anyway.
     
    Last edited: Feb 9, 2005
  5. Panuraj

    Panuraj Member

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    True enough.

    In the process of transferring, encoding to MPEG2, trimming/editing, and authoring and burning the DVD
    transferring is not the big waste of time, but I am somewhat taken aback about how slow these very powerful PC's are at processing video. Yes, I understand that these videos are huge and contain hundreds of thousands of frames each containing 720x480xwhatever of information, but I am still somewhat dismayed. It seems that the engine for capture video may have different requirement than the engine used to edit and process video, which in turn may have different requirements than the engine used to view vidoe's, but these three quite distinct functions are being bundled into a single consumer product.


    I also wondering if there is a peripheral DV tape device--not a camcorder-- designed for exactly this use: to transfer DV files quickly to efficient PC programs. I suspect not, but I can see few goods reasons to display the video during transfer or limit the transfer speed to playback speed.

    My best/easiest results right now come from transferrring files from my Replay TV 5504 to my PC. These are high quality MPEGs that don't need much editing, are reasonably sized.
     
  6. vurbal

    vurbal Administrator Staff Member

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    Capturing video really has very low requirements since it's just data transfer and only half the work is actually done by the pc. Encoding speed OTOH is almost completely dependent on your CPU (both the speed and any special instructions sets utilized by the encoder like SSE2 for CCE) so yes the requirements are vastly different for different operations. I don't find it surprising programs that do "everything" for you are so popular. Most people don't want to use multiple pieces of software to do things - even if it's cheaper, easier, and gives you better results. It's more work to find out what the best combination is and at least seems like more work to learn multiple programs.

    I don't know of such a device, and if it does exist it would probably be too expensive for me to worry about it. Right off the top of my head though I can think of the best possible reason why camcorders are limited to playback speed for transfer - price. If someone made a camcorder with high enough quality components to reliably transfer at higher speeds they'd also raise the price, and with the exception of people who already have the really high end camcorders I think most people would opt for better quality recordings and similar features rather than higher transfer speed if they were spending more money.
     
  7. TPFKAS

    TPFKAS Regular member

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    Yes Vurbal, I fully agree.
    As I stated in my earlier post, I do think that it is the camera that is the limiting factor. If you look inside the camera you can see it's a masterpiece of precision engineering and all very densly packed. Think about how dificult is must be to keep the tape positioned accurately agains the read/write heads. It is designed for normal operation. If you want it to operate at higher speeds as well, the requirements will go up and so is the price...
    Anyway, I am still amazed by the progress that has been made in this field since I started with digital video editing 10 years ago...
     
  8. Panuraj

    Panuraj Member

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    I agree.

    I don't mean to be badmouthing technological progress.
    My situation is not that I have a DV camcorder and will occasionally and selectively transfer to PC, but that I have come into possession of a large archive of DV tapes and was scoping the job of transferring the archive to DVD.

    Onesy-twosy, interactive products are just fine for normal consumer uses, but for production upload and transfer of large existing archives this might be present some real time issues. I'm just trying to get my arms around the time commitment.

    It suggests that I should pick and choose which of the existing tapes to transfer, or simply transfer as needed, but I don't think I can batch the whole lot of them very easily.
     
  9. Mark7

    Mark7 Member

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    I agree with you whole heartedly, Panuraj. The data stored on the DV tape should be able to be loaded much easier and faster as a raw file directly to your hard drive. But there seems to nothing available on the market right now to do so. The processors within the current crop of camcorders have more than enough power to do this. They could easily use a fast forward type function, bypassing the time consuming LCD display, and keep up for a much faster raw file transfer. But right now they choose not to. Most likely reasons have to do with their own propritory storage and encoding methods.

    Maybe in the near future....
     

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