Doom9's Forum - View Single Post - Will there be quality loss for YV12-> RGB32 -> YV12 colorspace conversion?

zee944 · 26th November 2012, 21:32

I've a problem related to this. I've learned from this topic how to do YV12<-->RGB32 conversion without chroma shift, but in-between I have to do some cropping as well. When I use even numbers to crop, everything is fine:

Code:

  ConvertToYV24(chromaresample="point")
  MergeChroma(PointResize(width, height, 0, 1))
  ConvertToRGB32()

  Crop(10,104,-10,-100)

  # ...filtering, etc...

  ConvertToYV12(chromaresample="point")

  # ...further filtering, etc...

  AddBorders(10,104,10,100)

...but when I crop by odd values, things gets nasty:

Code:

  ConvertToYV24(chromaresample="point")
  MergeChroma(PointResize(width, height, 0, 1))
  ConvertToRGB32()

  Crop(10,105,-10,-99)

  # ...filtering, etc...

  ConvertToYV12(chromaresample="point")

  # ...further filtering, etc...

  ss=2
  PointResize(width*ss, height*ss)
  AddBorders(10*ss, 105*ss, 10*ss, 99*ss)
  PointResize(width/ss, height/ss)

The cropping by odd numbers (and adding the borders back eventually with supersampling) leads to heavy chroma shift, very noticeably on the red parts. I suspect that the PointResize() is responsible for this, but I don't know how to avoid it. Can you help?

26th November 2012, 21:32	#30 \| Link
zee944 Registered User Join Date: Apr 2007 Posts: 240	I've a problem related to this. I've learned from this topic how to do YV12<-->RGB32 conversion without chroma shift, but in-between I have to do some cropping as well. When I use even numbers to crop, everything is fine: Code: ConvertToYV24(chromaresample="point") MergeChroma(PointResize(width, height, 0, 1)) ConvertToRGB32() Crop(10,104,-10,-100) # ...filtering, etc... ConvertToYV12(chromaresample="point") # ...further filtering, etc... AddBorders(10,104,10,100) ...but when I crop by odd values, things gets nasty: Code: ConvertToYV24(chromaresample="point") MergeChroma(PointResize(width, height, 0, 1)) ConvertToRGB32() Crop(10,105,-10,-99) # ...filtering, etc... ConvertToYV12(chromaresample="point") # ...further filtering, etc... ss=2 PointResize(widthss, heightss) AddBorders(10ss, 105ss, 10ss, 99ss) PointResize(width/ss, height/ss) The cropping by odd numbers (and adding the borders back eventually with supersampling) leads to heavy chroma shift, very noticeably on the red parts. I suspect that the PointResize() is responsible for this, but I don't know how to avoid it. Can you help?