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  • Blackmagic Design

    Blackmagic as a cross-platform codec on Mac and PC

    Posted by B. Rordin on July 6, 2006 at 2:35 pm

    We’re running Combustion 4 on Mac and on PC workstations. I did notice that Blackmagic QuickTime files give different result if I open them on the Mac or on the PC. For example I key a blue box on a PC then save the Combustion workspace and then open the same workspace on a Mac. The key gives different result. First I thought that it is a Combustion problem and decided to do a little test. I’ve captured a Blackmagic PAL 10bit file using FinalCut. Then I created DPX files out of it using Framelink. I opened the QuickTime and the DPX both on PC Combustion and Mac Combustion. I measured the RGB values of the first and the second pixel on the first row of a same frame. The values were different between both platforms plus DPX and Quicktime had different values on the same Mac. Bellow are the values in R/G/B format.

    Pixel 1
    Mac / MOV: 85/71/82
    Mac / DPX: 85/71/81
    PC / MOV: 162/157/214

    Pixel 2
    Mac / MOV: 509/485/511
    Mac / DPX: 507/483/908
    PC / MOV: 682/683/783

    So this brings some quiestions:
    1. Is this behavior normal?
    2. What is the correct workflow with Blackmagic files when Combustion has to be run both on PC and Mac for the same project?
    3. Which way gives the most true color in Combustion: opening the Quicktime or opening a DPX sequence produced in Framelink?

    Sean Oneil replied 19 years, 10 months ago 3 Members · 4 Replies
  • 4 Replies

  • B. Rordin

    July 7, 2006 at 9:37 am

    I just did the same in Shake. The results are different again:

    Pixel 1
    Mac / MOV: 85/71/82
    Mac / DPX: 85/71/81
    PC / MOV: 162/157/214
    Shake / MOV: 85/72/81
    Shake / DPX: 134/117/130

    Pixel 2
    Mac / MOV: 509/485/511
    Mac / DPX: 507/483/908
    PC / MOV: 682/683/783
    Shake / MOV: 504/483/511
    Shake / DPX: 578/556/579

    So what do you think?

  • Bj Ahlen

    July 8, 2006 at 6:40 pm

    DPX is a log format, so it will only give identical RGB values where the log curve intersects the linear curve.

    Mac<->PC could be a problem of different gamma.

  • B. Rordin

    July 10, 2006 at 2:29 pm

    I did a check with SD tiff file with known RGB values outputed on a Mac and PC Combustion via SDI. The Mac gave slightly darker picture. Is it Combustion’s fault or Decklink output compoment’s fault or is it Quicktime?

    Please guys we really need to clear this up! All this codec issues and inconsistency on Mac and PC are not good for our crossplatform workflow at all… Any inside information will be really useful.

  • Sean Oneil

    July 12, 2006 at 12:57 am

    I’d appreciate it if someone could clarify what’s going on here. It sounds serious.

    Sean

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