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SDI Capture

Discussion in 'Digital Video' started by dansai, Feb 17, 2008.

  1. macrumors newbie

    #1
    Hi, here's a quick question for the video gurus :)

    Using a new 2008 model 2x3.0ghz Octo-Core Mac-Pro (4gig ram), what sort of INTERNAL RAID set-up should I be using to capture uncompressed 1080p? I read a forum post a while back specifying that you should ideally have a 5-drive RAID-0 set-up if you want to capture HD-SDI reliably, but that was dated August 2005, so I'd like to assume things have changed since then.

    I can only really afford to have a 3 drive raid due to physical space in the pro, but I guess I *could* use an external as the boot drive. Also, EDITING this video could be a pain too, I'm guessing... Mainly if I have more than one stream playing in a project at once, right? I really don't know, as I've only ever used SD uncompressed (easy with only one drive, even) and DVCPRO (again, works with one drive no problem).

    What are you opinions?

    Thanks,
    Dan
     
  2. macrumors newbie

    #2
    your 8x3 shouldnt have any problems with playback. i would personally go with a RAID 0+1 set through a SCSI controller card. if you went external, then you could use more drives.
    ~cheers
     
  3. macrumors regular

    #3
    I may not be understanding your specs properly, but it sounds like you might be working with very high data rates. From the information you provide, "HD-SDI" and "uncompressed 1080p," do you mean high-end dual-link HD-SDI (2.970 Gb/s)? Are you wanting to sample 10-bit, 4:4:4?

    Depending on your exact setup, three SATA drives in your Mac Pro probably will NOT deliver the kind performance you are looking for. Uncompressed HD needs a LOT of sustainable throughput. For that, you need very fast drives (you will typically see expensive fiber channel or SCSI RAIDs used for this application). You also want a dedicated RAID controller to free up that load on the computer.

    If you provide your capture and edit format, I'm sure someone here can point you toward the likely disk specs you will need. Also, what capture I/O device are you using with your Mac?
     
  4. macrumors newbie

    #4
    Hi, thanks for the replies.

    I plan on capturing 1080F (basically it's true 30fps 1080p but in a 60fps 1080i stream, which can be patched quickly once captured) via HD-SDI from a Canon XL-H1 camera.

    I don't know the specifics, but the camera's manual states that it requires a steady throughput of 99 MB per/sec (that's Megabytes), or 132MB per/sec if I want to transfer in 10bit mode (but as this camera has an 8bit sensor this is largely pointless)

    So, I guess the real question is how can I configure a cost effective raid to sustain, say, 150MB p/s in a worst case scenario?

    Thanks
     
  5. macrumors demi-god

    LethalWolfe

    #5
    Why don't your capture as Pro Res? Comparable quality to uncompressed HD w/much more manageable file sizes.


    Lethal
     
  6. macrumors newbie

    #6
    That's a nice suggestion actually, I can't believe I didn't think about this before. What would I need to be able to (I'm guessing) transcode on-the-fly? Is it something that would be built into certain SDI cards? Or will any old SDI card work & the Mac Pro does the work?

    Dan
     
  7. macrumors regular

    #7
    Wait - I don't get it.

    The "Canon XL-H1 camera" shoots on Mini-DV tapes and records in the HDV video format/codec.

    Capturing from HD-SDI output on playback will NOT give you a better signal or image than capturing as HDV via firewire.

    The only reason HD-SDI out is even useful for the Canon XL-H1 camera is because you can use it as a live camera. IE: Into a television switcher OR into a higher end tape deck - like a HDCAM or DVCPROHD deck.


    If you're using the Canon XL-H1 camera you don't even need a raid for capturing... Only really for size... and only if you're using LOTS of footage/media.
     
  8. macrumors demi-god

    LethalWolfe

    #8
    As long as you are using FCP 6 on a Mac Pro and have a card w/HD-SDI you can capture into Pro Res on the fly, AFAIK.

    Or you can capture straight into FCP if your workflow allows the camera to be tethered to a desktop machine. I assumed this is what the OP was doing, but we all know the problems w/assumptions. ;) Yes, if the OP is shooting to tape then capturing the best bet would be to capture as HDV over firewire and change the sequence settings so the rendering is done in the Pro Res codec and not in HDV.


    Lethal
     
  9. macrumors regular

    #9
    Ah, the specs make all the difference in the world. When the OP first mentioned uncompressed HD-SDI, I was thinking in terms of more professional grade gear. Since this camera is working with already compressed HDV video, firewire does seem the natural choice for transfer.

    BUT, if the HD-SDI connection must be used for whatever reason, you still will need a RAID system for those kinds of data rates. One option would be to buy a 5-drive+ RAID mini-tower (for example, from Medea/Avid) with a SCSI interface. I have become more of a fan of the cheaper External-attached SATA port-multiplying boxes for small editing projects. For about half to three-quarters of that price, you can set up your own RAID tower. Check out the products from Sonnet Technologies if you are interested in this route. Keep in mind that the cheaper choices often do not have dedicated internal RAID controllers, so the additional work of maintaining the array is placed on the main computer.
     

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