[FFmpeg-user] Does converting to yuv444p by default make sense?
thljcl
jiachielee at live.com
Mon Jul 29 13:14:04 CEST 2013
YCbCr is not an absolute color space. It’s just a way to represent all color
information in RGB in different set of “coordinates”. Mathematically
speaking, YCbCr 4:4:4: is related to RGB color space by a single linear
transformation matrix, just like Lorentz Transformation or Rotation in
Euclidean Space. Now I know that there are different standards with regards
of the transformation matrix being used; but all of them are non-singular,
or reversible. That said, when it comes to calculation by computer, there
will always be rounding involved. However, no rounding error would be
introduced in this case because number of colors in RGB color space is
limited. For 24-bit sRGB color space, there are only 16,777,216 colors;
whereas the usual coordinate transformation involves vector space which can
be seen as a set of infinite elements of coordinates.
That said, by encoding RGB color space in Y, Cb, and Cr channels, we can
later reduce the number of bits being used for encoding color information in
Cb and Cr channels; that’s the basic idea behind chroma subsampling. In case
you wonder how a chroma subsampling scheme affects the number of bits to be
used for a single pixel on average:
LAGS NAME NB_COMPONENTS BITS_PER_PIXEL
-----
IO... yuv420p 3 12
IO... yuyv422 3 16
IO... rgb24 3 24
IO... bgr24 3 24
IO... yuv422p 3 16
IO... yuv444p 3 24
IO... yuv410p 3 9
IO... yuv411p 3 12
IO... gray 1 8
IO..B monow 1 1
IO..B monob 1 1
I..P. pal8 1 8
IO... yuvj420p 3 12
IO... yuvj422p 3 16
IO... yuvj444p 3 24
..H.. xvmcmc 0 0
..H.. xvmcidct 0 0
IO... uyvy422 3 16
..... uyyvyy411 3 12
IO... bgr8 3 8
.O..B bgr4 3 4
IO... bgr4_byte 3 4
IO... rgb8 3 8
.O..B rgb4 3 4
IO... rgb4_byte 3 4
IO... nv12 3 12
IO... nv21 3 12
IO... argb 4 32
IO... rgba 4 32
IO... abgr 4 32
IO... bgra 4 32
IO... gray16be 1 16
IO... gray16le 1 16
IO... yuv440p 3 16
IO... yuvj440p 3 16
IO... yuva420p 4 20
..H.. vdpau_h264 0 0
..H.. vdpau_mpeg1 0 0
..H.. vdpau_mpeg2 0 0
..H.. vdpau_wmv3 0 0
..H.. vdpau_vc1 0 0
IO... rgb48be 3 48
IO... rgb48le 3 48
IO... rgb565be 3 16
IO... rgb565le 3 16
IO... rgb555be 3 15
IO... rgb555le 3 15
IO... bgr565be 3 16
IO... bgr565le 3 16
IO... bgr555be 3 15
IO... bgr555le 3 15
..H.. vaapi_moco 0 0
..H.. vaapi_idct 0 0
..H.. vaapi_vld 0 0
IO... yuv420p16le 3 24
IO... yuv420p16be 3 24
IO... yuv422p16le 3 32
IO... yuv422p16be 3 32
IO... yuv444p16le 3 48
IO... yuv444p16be 3 48
..H.. vdpau_mpeg4 0 0
..H.. dxva2_vld 0 0
IO... rgb444le 3 12
IO... rgb444be 3 12
IO... bgr444le 3 12
IO... bgr444be 3 12
I.... gray8a 2 16
IO... bgr48be 3 48
IO... bgr48le 3 48
IO... yuv420p9be 3 13
IO... yuv420p9le 3 13
IO... yuv420p10be 3 15
IO... yuv420p10le 3 15
IO... yuv422p10be 3 20
IO... yuv422p10le 3 20
IO... yuv444p9be 3 27
IO... yuv444p9le 3 27
IO... yuv444p10be 3 30
IO... yuv444p10le 3 30
IO... yuv422p9be 3 18
IO... yuv422p9le 3 18
..H.. vda_vld 0 0
IO... gbrp 3 24
IO... gbrp9be 3 27
IO... gbrp9le 3 27
IO... gbrp10be 3 30
IO... gbrp10le 3 30
I.... gbrp16be 3 48
I.... gbrp16le 3 48
IO... yuva420p9be 4 22
IO... yuva420p9le 4 22
IO... yuva422p9be 4 27
IO... yuva422p9le 4 27
IO... yuva444p9be 4 36
IO... yuva444p9le 4 36
IO... yuva420p10be 4 25
IO... yuva420p10le 4 25
IO... yuva422p10be 4 30
IO... yuva422p10le 4 30
IO... yuva444p10be 4 40
IO... yuva444p10le 4 40
IO... yuva420p16be 4 40
IO... yuva420p16le 4 40
IO... yuva422p16be 4 48
IO... yuva422p16le 4 48
IO... yuva444p16be 4 64
IO... yuva444p16le 4 64
..H.. vdpau 0 0
IO... xyz12le 3 36
IO... xyz12be 3 36
IO... rgba64be 4 64
IO... rgba64le 4 64
..... bgra64be 4 64
..... bgra64le 4 64
IO... 0rgb 3 24
IO... rgb0 3 24
IO... 0bgr 3 24
IO... bgr0 3 24
IO... yuva444p 4 32
IO... yuva422p 4 24
IO... yuv420p12be 3 18
IO... yuv420p12le 3 18
IO... yuv420p14be 3 21
IO... yuv420p14le 3 21
IO... yuv422p12be 3 24
IO... yuv422p12le 3 24
IO... yuv422p14be 3 28
IO... yuv422p14le 3 28
IO... yuv444p12be 3 36
IO... yuv444p12le 3 36
IO... yuv444p14be 3 42
IO... yuv444p14le 3 42
IO... gbrp12be 3 36
IO... gbrp12le 3 36
IO... gbrp14be 3 42
IO... gbrp14le 3 42
IO... gbrap 4 32
I.... gbrap16be 4 64
I.... gbrap16le 4 64
IO... yuvj411p 3 12
The short answer: YUV444 can fully represent all color information in RGB.
--
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