#4 4:4:4 and 10 bit

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nobody
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5
2005-02-19
2005-02-19
Anonymous
No

I hope anybody have thought about supporting YUV
4:4:4 and 10 bit per color channel.
That would allow the use of Dirac inside professional
environments.
I'm tired of seeing the Open source community is giving
its back to anything higher than 8 bit per color channel...

Discussion

  • Tim Borer

    Tim Borer - 2005-02-21

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    Since the developers come from a broadcasting background
    we are well aware of the need for high quality compression fro
    professional environments.

    We plan to support 4:2:0, 4:2:2, 4:1:1 and 4:4:4. In addition
    we plan to support RGB and luminance only.

    The number of bits per pixel is a more complex issue. Since,
    at the moment, Dirac is a lossy compression system (not too
    lossy we hope!) in 10 bit systems it is likely that the bottom
    two bits from decompressed Dirac will not be the same as
    those that go in except at very high bit rates. In this respect
    the number of bits at the output is simply a matter of output
    formatting.

    On the input side it is generally better to take in as much
    infromation as possible prior to compression to get best
    results. How this information is used internally is subject to
    further developement. Increasing the number of bits from 8 to
    10, internally, may have a disproportionate impact on
    performance whilst not yeilding any improvements in quality.

    I think it is work bearing in mind that 10 bit professional video
    was originally only using extra two bits, originally designated
    spare, on the D parrallel digital interface. They were only used
    becuase they were there. At that timethere was considerable
    debate about the need for these extra bits. I think it is
    generally agreed that when cascading processing these extra
    bits are helpful. That said, processes like error feedback and
    dynamic rounding mitigate the effects of only using 8 bits.

    The bit stream syntax that the team and I are currently
    drafting, and which we hope to release for comment very
    soon, will include explicit support for 10 bit video.

     
  • Gatak

    Gatak - 2005-03-05

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    The 8bit vs xxbit debate has been a long one, especially
    amongst Photoshop users. Some say there is no difference,
    other say it mean life and death.

    For me, I would be very happy to have 4:4:4 support before
    higher bit depth, simply because it yields much better
    improvement of quality, rendering at 24bits per pixel instead of
    16 or 12 which is usual.

    Most TV content isn't badly affected by the lower resolution
    chroma channels of 4:2:0/4:2:2 because colors aren't very
    saturated to begin with. However for CG and otherwise high-
    hightrast and colorful content there is a clear difference.

    An example I've made to illustrate: http://moment22.mine.nu/
    yuv.png - remember this is with no compression. No matter
    what bitrate you use this would be the best result.

    Higher bit depth could certainly make a difference if the video
    is to be post edited. otherwise we are limited to the output
    resolution, which is 8bits per channel, unless using some
    special hardware. The analog video-signal itself can probaly
    contain much more detail than 256 levels...

    If you want to post-edit image/video then you certainly can use
    all the extra levels/bits. This is obviously visible in the digital
    camera market where 12bits and more is standard.

     
  • Gatak

    Gatak - 2005-03-05

    Logged In: YES
    user_id=820001

    The 8bit vs xxbit debate has been a long one, especially
    amongst Photoshop users. Some say there is no difference,
    other say it mean life and death.

    For me, I would be very happy to have 4:4:4 support before
    higher bit depth, simply because it yields much better
    improvement of quality, rendering at 24bits per pixel instead of
    16 or 12 which is usual.

    Most TV content isn't badly affected by the lower resolution
    chroma channels of 4:2:0/4:2:2 because colors aren't very
    saturated to begin with. However for CG and otherwise high-
    hightrast and colorful content there is a clear difference.

    An example I've made to illustrate: http://moment22.mine.nu/
    yuv.png - remember this is with no compression. No matter
    what bitrate you use this would be the best result.

    Higher bit depth could certainly make a difference if the video
    is to be post edited. otherwise we are limited to the output
    resolution, which is 8bits per channel, unless using some
    special hardware. The analog video-signal itself can probaly
    contain much more detail than 256 levels...

    If you want to post-edit image/video then you certainly can use
    all the extra levels/bits. This is obviously visible in the digital
    camera market where 12bits and more is standard.

     
  • Gatak

    Gatak - 2005-03-05

    Logged In: YES
    user_id=820001

    Hm, odd that there was a second copy of my post.

    Anyway, what I was trying to say was that although 8bits is
    not much for images when you post process, it should be
    enough for video which is already pre-processed (perhaps at
    higher bit depth).

     

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