• Blackmagic Design

  BM 8 Bit Codec renders DARKER in QT

  Posted by David Fortin on November 22, 2005 at 3:25 pm

  I

  David Phillips replied 20 years, 5 months ago 4 Members · 3 Replies
• 3 Replies

• 

  Luke Maslen

  November 23, 2005 at 5:44 am

  Hi David,

  This is a complex topic and the answers vary over time due to changes in the Apple codecs.

  The current situation is that Apple codecs automatically gamma-correct for the display you are using. Every display is different and so the same movie will appear differently on different displays which can be confusing. We never liked that idea and so the Blackmagic codecs output consistant gamma regardless of the display you use. Hence the fact that you may see a difference when switching between Apple and Blackmagic encoded files, and ours will often look darker.

  However the important thing is that, no matter how the image may appear on your computer screen, it must be consistant on the broadcast monitor attached to your DeckLink card. So the real test is to open Apple and Blackmagic encoded movies and output them to your broadcast monitor and compare them only on that monitor.

  The good news is that we’ve been working with Apple to overcome these issues. Apple have encouraged us to adopt their codecs in place of our own to avoid gamma shift issues. We’ve done that wherever possible but there are still a few places where our codecs are required. While Apple have added a HD color space to their uncompressed 8 and 10-bit 4:2:2 codecs in Final Cut Pro HD 5.0, they have not yet added a RGB color space. Accordingly when working with both Final Cut Pro (YUV) and After Effects (RGB), we still need to invoke our codec so that a correct color space conversion is performed. When you go to export from After Effects, we hide the Apple Uncompressed codecs to ensure the Blackmagic codecs are used. However when working in Final Cut Pro, we always invoke the Apple codecs with any Blackmagic easy setup. The only exception to this is that we use our codec for use in 4:4:4 high definition work as Apple do not yet include a HD codec with RGB color space.

  In regards to the Blackmagic 8-bit 2Vuy codec, this is the same as the Blackmagic 8-bit codec except it has a different header and is compatible with legacy Cinewave files. Please adopt the Blackmagic 8-bit or the Apple 8-bit codecs as they are both compatible with the 2vuy standard rather than the older 2Vuy standard. There is a support note about this named Why are there multiple 8-bit codecs?. If you really need to work with the Blackmagic 8-bit 2Vuy codec for some reason, then please refer to the support note How do I work with Cinewave files without rendering? NTSC.

  I hope this helps clarify some of these mysteries and please let me know if further clarification is required.

  Regards,

  Luke Maslen
  Blackmagic Design
• 

  Mark Cookman

  November 24, 2005 at 9:34 pm

  well I was glad to read that “refresher” thanks for writing it 🙂
• 

  David Phillips

  November 29, 2005 at 4:26 pm

  Luke,

  I am experiencing similar problems coming from Shake 4. I am processing 1080 23.98psf clips from FCP (captured by a BM DL HD, so Apple UC 10-bit 4.2.2) When I bring the renders back into FCP, the gamma shifts. Which codec should I render to, BM 10-bit (DV10) or BM 10-bit (RGB)?

  thanks,
  david

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