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User16460825278372561352 (Vital Passenger) asked a question.

April 30, 2022 at 3:08 AM
I'm seeing strange red blocking after encoding Profile 7 Dolby Vison using x265. Is there a known issue that might cause this?
The blocking moves around the image. It seems to get better as the bit rate is increased, but never goes away fully. See Attached. So far, I only see it in graphics. Does not seem to show up in film/grain video. This image was encoded at 74Mbps.
  • 3 answers

  • kciec (Dolby Labs)

    Hi can you let us know about your setup? Which version of DEE do you use? Which version of x265? On what operating system (Windows/Linux) do you work? Also, regarding DEE, do you use the default parameters provided within XML configs, or have you tuned them somehow? Thanks.

  • User16460825278372561352 (Vital Passenger)

    sure thing.
    Dolby Encoding Engine with AC-4-v5.1.0.
    I built x265 as in the DEE documentation.
    libx265.dll shows version as 3.1.0.1.
    on Windows 10 pro.
    Doing MEL with no mapping.
    The above image was using default xml configs.
    Only changed the bit rates to 74Mbps. However, still see red blocking around text at default rate, (I think it's 99Mbps) but it's not nearly as bad, but still quite noticeable.

    Here is a link to a snippet of the footage being encoded:
    https://severin-films.filemail.com/d/sttgpsnnuknxphw

    Also, I don't see this problem when using stand alone x265, albeit a newer version.
    Expand Post

  • kciec (Dolby Labs)

    Thanks for the details. It seems the problem lies in the x265 library, and it occurs only on Windows version (the Linux version works well).
    Probably the newer version is not affected by this issue, so you don't see this when you use the standalone version. BTW what do you mean by standalone version?
    Also, as a workaround, you can try to use the 0 value for cbqpoffs and crqpoffs (you can change them in the DEE XML config for the hevc encoder).

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