• Avid Media Composer

  Blue screen keying in Avid Symphony 5 Nitris DX

  Posted by John Watts on February 18, 2011 at 4:23 am

  So we are enjoying our new Avid Symphony but have run into some issues with getting a clean chroma key with HD footage.
  We had a Panasonic AG-AF100 camera in the studio for some testing. Shot a single human subject against a well and evenly lit blue screen. The camera uses AVCHD 4:2:2. We tested 1080i, 720p.
  Using Spectramatte has resulted in the best key so far, but it’s not satisfactory. The footage is brought in by importing into a bin directly from the SD card it was recorded on.
  Have also tried the Boris keyer with similar results. Also, downloaded and tried the demo version of the latest Ultimatte. That did yield better results with little key adjustment, but the render time was absolutely ridiculous! Something like 35 to 1, with an 8 core machine…yuk!
  We’re considering not using the AVCHD that comes with the camera and going with a nanoflash drive to go straight to quicktime or MXF.
  Any input, ideas or ramblings would be appreciated as we consider the options to make our keying look better.

  John Watts

  Michael Kammes replied 15 years, 3 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Hector Berrebi

  February 18, 2011 at 12:37 pm

  [John Watts] “The camera uses AVCHD 4:2:2. We tested 1080i, 720p.”

  Jhon

  no, actually, the camera uses 4:2:0 AVCHD like all flavors of this format except for the very different AVC-intra. being also a long GOP format, its less than favorable for keying

  if you record to a Ki-pro or a nano you will up it to 4:2:2 on an I-frame format and higher bit rates which will all significantly improve your keying.

  i have tested the AG 100, both native and to a Ki-pro and there are differences in chroma levels easily measured on standard scopes.

  didn’t test nano, but at high bit rates it should yield similar results.

  one more thing, as great a tool Spectramatte is, it is by far not the best keyier around, and avid not the ideal keying platform. it does give good and often satisfying results. you can always get better with more relevant tools

  Hector Berrebi
  prePost Consulting
• 

  John Watts

  February 18, 2011 at 4:32 pm

  Thanks.
  The more info about AVCHD I get the more realization that it won’t bode well for keying.
  This will probably insure that we go with Nanoflash or KiPro.
  In our old Meridian Avid we do have Ultimatte for the chroma keys and it did a pretty good
  job (still works too).

  John Watts
• 

  Michael Kammes

  February 18, 2011 at 5:59 pm

  Foe best results, bring the footage in and transcode down to a flavor of DNxHD, and key off of that. Much better. Yes, you take a hit in time to create the initial DNxHD file, but it pays off later because you save time on the transcode for export, plus, the playback of the key will be easier on the machine (less potential stutter)

  ~Michael

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