SONY CX RAW UNCOMPRESSED FILES.

Discussion in 'Cameras' started by Alex Smart, Sep 29, 2013.

  1. Alex Smart

    Alex Smart Member

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    Hi !
    I´ve heard that some people are hacking the sonny CX cameras using ¿an external memory file converter device?
    to obtain raw uncompresed files!!
    Any experts out there that could confirm this??
    Many thanks!
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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  3. Alex Smart

    Alex Smart Member

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    Is HDMI used for video downlink?
    The hack Im talking about would basically colect the uncompressed files in an external device,raw footage + Boss would deserv a reverence!
    Then again, I dunnot have a suficient understanding on the matter, I could be talking BS!:D
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The issue is not BS, Alex. The issue is BW (bandwidth -- the ability of a transmission link to carry data). It's all about how much data you can transmit and how fast you can transmit it. And for High Def video you need to consider how many frames per second, at what resolution (in terms of pixels), the color depth (how many binary digits are assigned for color rendition), and whether or not there can be some compression (and whether it can be lossless or lossy).

    Check out, for example, http://www.ciena.com/connect/blog/How-much-bandwidth-does-Broadcast-HD-video-use.html
    There is an example on that page that says, uncompressed 1920x1080 at 59.94 fps with 48-bit color depth (without so-called chroma subsampling), will require 6.6 Gigabits per second. That's one large amount of data to be sent. There are tricks to reduce (e.g. compression), but it's still like drinking from a fire hose.

    Then you have to consider the radio frequency that is being used to transmit the signal -- there is an upper bound to the data rate that you can send at, say, 5.8 Ghz. I ran out of time to look this up on the web, but there is a definite physical limit. (EDIT: Based on the table here it looks like, depending on the the number of channels (also, unfortunately called bandwidth), at 5 Ghz, the maximum is 866.8 megabits per second. Which is a small fraction of what you need without compression.)

    If you add compression, you also add time delays for the compressing in the transmitter and uncompressing in the receiver.

    So, bandwidth is the issue....
    Andy.
     
  5. Steve Maller

    Steve Maller UAV Grief Counselor

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    Andy, I think Alex may just be asking about collecting uncompressed video onboard the copter itself, not necessarily downlinking it. But that said, your numbers are relevant because it's even difficult to get a flash memory card that's fast enough to write an uncompressed HD video stream. Witness the challenges that the Magic Lantern hacks have with the CF cards in the 5D Mark III.

    And at the end of the day, I doubt that the CX-760V's raw video stream is actually worth all that trouble. It's a good camera, no doubt, but I'd focus my efforts on something like the Black Magic pocket camera, instead.
     
  6. Alex Smart

    Alex Smart Member

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    Hi Andy!
    Im gonna dig that link!!
    But just to clear the nature of the thread,my fault,probably not explaining my self properly:
    Im not talking about transmiting the date through video downlink.
    Im talking about jumping the AVCHD recording format and recording raw/60p files on an external memory device!
    Does it make sence:confused:?
     
  7. Alex Smart

    Alex Smart Member

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    Yes!that was it, so you dont recon its worth the shot? I was just imagening RAW+BoSS!!
    Anyways..
    Thanks!
     
  8. Gary Haynes

    Gary Haynes Administrator
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  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    IMHO, no.
     

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