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Some hope for a higher bit rate in the future?

Discussion in 'Zenmuse X5' started by InterMurph, Oct 16, 2015.

  1. InterMurph

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    Lynh Phan posted some photos on Facebook that show the guts of the X5 camera:

    Facebook

    This one shows the SoC (processor), which is marked "Ambarella A9-A1-RH".

    The Ambarella Data Sheet for the A9 SoC doesn't mention bit rates, it but it does say:
    On the H.264 Wikipedia page, BP is "Baseline Profile (66)", MP is "Main Profile (77)", and HiP is "High Profile (100)".

    But it is the "Level 5.1" that has me hopeful. On the Wikipedia page again, under "Max video bit rate for video coding layer (VC) kbit/s", under level 5.1, it specifies 240,000 for BP and MP, and 300,000 for HP. That's 240 and 300 megabits/second, respectively.

    And if we move down to Level 4.2, we find that the max bit rate for HP is 62,500 kbit/s, or about 60 megabits/second, which is what we are getting from the X5 right now.

    So my hope is that the X5 camera is currently not asking the Ambarella chip to do all that it can, and that the Ambarella chip can be unleashed in a future upgrade.
     
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  2. Quadpilot

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    Just remember that the A9 isn't just encoding for the microSD card, but also a separate stream for Lightbridge. That takes away some of the SoC's headroom for the H.264 encoding.

    Part of the issue in terms of bit-rate is that it may be constrained by heat issues. There is a fan in the X5 to take away the heat generated by the CPU and ARM, but DJI may have had to throttle the chip to avoid excessive heat build-up in the camera.

    Anyway, like you, I hope it can be improved, if possible.
     
  3. InterMurph

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    If that's the case, then I would like to see a switch that lets me choose "100 mbits/s to SD with 15 FPS to Lightbridge" over the "60 mbits/s to Sd with 30 FPS to Lightbridge" that we have now.
     
  4. AutoAir

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    It's the same processor that is in the gopro hero 4. In the hero 4 its running 60Mb/s so unless it's really future proofed I doubt it.
     
  5. InterMurph

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    But as far as I can tell, the A9 chip is spec'ed for a much higher bit rate. The fact that two major customers use a lower bit rate is a clue, but not proof, that it is not capable of higher rates.

    I remain hopeful.
     
  6. ianwood

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    If the A9 were only writing one stream to SD, it could be higher than 60Mbps. But, given that it's outputting two streams, the one written to SD will not get far past 60Mbps. Maybe if DJI dropped the live preview down to 480p, they could write 65Mbps to the card like the GoPro does. But that's about it.
     
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  7. Morgon

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    Well, dual A9s is the only answer. Let's just put one in each arm.

    In seriousness though, Ambarella has a newer chip called the H1, that was announced earlier this year. No spec sheet for it yet, though. Anyway, I'm curious if that would be a successor to the A9. 4Kp60 (in h.264) sounds like fun times.
     
  8. Burlingtonfilms

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    Would be awesome if this is made into an update.

    The only reason I haven't bought an X5 yet is the low bit rate.

    Most productions I work on shoot in RAW. Though the Inspire 1 is great for quick master shots, trying to use it for longer jib/crane/dolly types of shots don't make the cut. The difference is quality shows when the Inspire 1 shot is played for too long.
     
  9. Fredrik Alden

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    I doubt that DJI will update this, as it would compete with their own X5R.
     
  10. InterMurph

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    There is a $3,300 price difference between the X5 camera and the X5R camera. That premium is for the raw video feature. There is plenty of room at the lower end to bump up the compressed-video bit rate.
     
  11. Quadpilot

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    Hoping and wishing won't make it so, however. ;)

    I can't imagine that DJI would change the SoC to the H1 so soon after X5 release. It would require a whole new suite of software to optimize the chip for the MFT sensor and would require H.265 adaptation as well. Not saying it won't ever happen (X5s?) but not for quite awhile. In the meantime, we can only hope that there is some way that doesn't run into heat issues to bump the X5 bit-rate.
     
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