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Video Resolution Formats and Bitrate / Data Rate

Discussion in 'Pro/Adv Discussion' started by loganboyd, May 14, 2015.

  1. loganboyd

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    I recorded short videos in all of the allowed NTSC video formats so that I could see that Bitrate / Data rate of the videos.

    4096x2160 @ 24fps - 60mbps
    3840x2160 @ 24fps - 60mbps
    3840x2160 @ 30fps - 60mbps
    1920x1080 @ 60fps - 40mbps
    1920x1080 @ 48fps - 40mbps
    1920x1080 @ 30fps - 25mbps
    1920x1080 @ 24fps - 25mbps
    1280x720 @ 60fps - 20mbps
    1280x720 @ 48fps - 16mbps
    1280x720 @ 30fps - 10mbps
    1280x720 @ 24fps - 8mbps

    If you want to know how much video you can record on a certain size memory card you just have to use the total capacity of your card divided by the bitrate.
    For example. the 16GB card shipped with the P3 could record any of the 4K formats for the same length of time since they produce the same bitrate.
    16,000,000,000 bytes / 60,000,000 bits per second X 8 bits per byte = 2,133 seconds or 35.55 minutes.
    You won't get exactly this much because the formatted card won't give you exactly 16GB and the bitrate may fluctuate beteen 58mbps and 61mbps.
    A good rule of thumb is for every 1GB of memory card you can record for 2 min in any of the 4K formats.
     
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  2. Serpent

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    Well researched.
    Given the top data rate of 60mbs, that's means 25% more data is stored per frame/key framed sequence for 24fps over 30fps (for comparable resolutions). I wonder how that looks on the playback screen in terms of definition?
    The top resolution is 6.66% more width + total pixels over the next step down. Marginal difference although 'wider' widescreen tends to be favourable to boxier formats.
    Unless filming moving targets or doing a lot of panning, the picture doesn't change so rapidly so 24fps is likely acceptable for most people's requirements. 30fps should look smoother.
     
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  3. CallMeAlan

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    Yes, I calculated .45 Gb per minute at 4K. I've recently bought (rented?) Premiere Pro CC to replace FCP X. PPro makes export a little more complicated than FCP X and I've been experimenting with various export settings. With a source bitrate of 60 there's no real point in exporting at anything greater than that, UNLESS you're sticking titles, lower-thirds, etc, over the footage, then a jump to 85 on export is worthwhile, otherwise you get a sort of interference pattern at the edges of the lettering. All my export is in VBR. But I discovered that with VBR my TV (Samsung curved 55 inch 4K) does NOT like stills included in the movie, presumably because in VBR the bitrate is very low during the still. So if you want to include stills in your movie use CBR. It's a learning curve for sure!
     
  4. JayB

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    I read a review on the forum for the shipped SD card, they tested the speed which showed that the write speed was approximately 45mbps, half that of the read speed.
     
  5. UKFlyer

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  6. J.J.B.

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    Don't suppose anyone with more electronics expertise than me has worked out whether it's possible to output to a Ninja Star from a P3 yet?
     
  7. loganboyd

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    I think y'all are confusing MB/s with mbps. Megabytes per second vs megabits per second.
    The cards are 633x mean 633x 150 KB/s = 95MB/s (760mbps) but that is for READ speed. Write speed is slower but probably still somewhere at least half of that which would be around 380mbps and our cameras are writing at 60mbps.

    I did some benchmark testing on the 64GB version of the Lexas 633x MicroSD card.

    This first benchmark shows 74MB/s 592mbps sequential read and 45MB/s 360mbps sequential write.
    Capture.PNG

    This next benchmark is more detailed as it is writing 256MB of data to the card in different size chunks from 2KB up to 1,024KB.
    You can see the Write Speed doesn't start to perform well until you attemp to write 64KB chunks or larger.
    Also Read Speed doesn't hit its stride until you get to the same 64KB block size.

    Capture2.PNG

    All of these data transfers at the 64KB size and larger are MORE than fast enough to handle the 7.5MB/s 60mbps throughput of the 4K video stream.
     
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