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Comparing YUV conversion approaches.

This is comparing different ways to do the YUV conversion. We are doing it in both 420p and 444p since 444p is a fairer binary image comparison. The takeaway should be to use the libswscale filter. The code to generate these files is here.



YUV420p encodes





YUV444p encodes (Chrome Only)






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Reference PNG

Source PNG file

YUV420p encodes

Default Encode (terrible)

Basic ffmpeg conversion, no colorspace specified, ffmpeg assumes bt601 colorspace. This is a terrible filter, significant color changes from PNG file.

ffmpeg flags to add:

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -c:v libx264 -preset placebo -qp 1 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv420p -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/basic.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-basic.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-basic.png"
Mean error = 0.0212507
RMS error = 0.0388912
Peak SNR = 28.203
Max error = 0.556863 @ (1815, 1004, B) values are 0, 0, 0.952941 vs 0.0705882, 0.0901961, 0.396078
1792353 pixels (86.4%) over 1e-06
1792353 pixels (86.4%) over 1e-06
FAILURE
'ERROR!

Colormatrix filter (close)

Using colormatrix filter. colormatrix only supports 8-bit per component images. Visually its getting pretty close.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709" -c:v libx264 -preset placebo -qp 1 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv420p -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/colormatrix.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-colormatrix.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-colormatrix.png"
Mean error = 0.00307147
RMS error = 0.0124281
Peak SNR = 38.1119
Max error = 0.568627 @ (1904, 1040, B) values are 0, 0, 1 vs 0.0666667, 0.0588235, 0.431373
1482440 pixels (71.5%) over 1e-06
1482440 pixels (71.5%) over 1e-06
FAILURE
'ERROR!

Colorspace filter

Using colorspace filter, better quality filter, SIMD so faster too, can support 10-bit too. Visually pretty close to colormatrix, but slight improvement based on colormatrix values.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -c:v libx264 -preset placebo -qp 1 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv420p -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/colorspace.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-colorspace.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-colorspace.png"
Mean error = 0.002964
RMS error = 0.0123796
Peak SNR = 38.1459
Max error = 0.564706 @ (1904, 963, B) values are 0, 0, 1 vs 0.0627451, 0.0588235, 0.435294
1473078 pixels (71%) over 1e-06
1473078 pixels (71%) over 1e-06
FAILURE
'ERROR!

libswscale filter + flags (best)

Using the libswscale library. Seems similar to colorspace, but with image resizing, and levels built in. This also has a number of libswscale parameters. Visually this is close to the above two, but slight improvement based on colormatrix results.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=tv:out_color_matrix=bt709"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=tv:out_color_matrix=bt709" -c:v libx264 -preset placebo -qp 1 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv420p -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/splinecolormatrix.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-splinecolormatrix.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-splinecolormatrix.png"
Mean error = 0.00260747
RMS error = 0.0131948
Peak SNR = 37.592
Max error = 0.627451 @ (1904, 963, B) values are 0, 0, 1 vs 0.054902, 0.0470588, 0.372549
1341240 pixels (64.7%) over 1e-06
1341240 pixels (64.7%) over 1e-06
FAILURE
'ERROR!

YUV444p encodes (Chrome Only)

Default Encode (terrible)

Basic ffmpeg conversion, ffmpeg assumes bt601 colorspace, now at 444. Results look terrible.

ffmpeg flags to add:

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/basic444.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-basic444.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-basic444.png"
Mean error = 0.0204761
RMS error = 0.0372786
Peak SNR = 28.5708
Max error = 0.152941 @ (1832, 618, G) values are 0.968628, 0, 0.968628 vs 1, 0.152941, 1
1779568 pixels (85.8%) over 1e-06
1779568 pixels (85.8%) over 1e-06
FAILURE
'ERROR!

Colormatrix filter (close)

Using colormatrix filter. colormatrix only supports 8-bit per component images. Visually pretty close, but still off.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709" -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/spline444colormatrix2.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444colormatrix2.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444colormatrix2.png"
Mean error = 0.00153716
RMS error = 0.00270346
Peak SNR = 51.3616
Max error = 0.0117647 @ (1389, 462, R) values are 0, 0.733333, 0.690196 vs 0.0117647, 0.737255, 0.694118
1434882 pixels (69.2%) over 1e-06
1434882 pixels (69.2%) over 1e-06
FAILURE
'ERROR!

Colorspace filter

Using colorspace filter, better quality filter, SIMD so faster too, can support 10-bit too. Visually slight differences, but getting closer.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/spline444colorspace.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444colorspace.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444colorspace.png"
Mean error = 0.00143352
RMS error = 0.0025418
Peak SNR = 51.8972
Max error = 0.0117647 @ (916, 308, B) values are 0.388235, 0.486275, 0.305882 vs 0.392157, 0.490196, 0.317647
1429294 pixels (68.9%) over 1e-06
1429294 pixels (68.9%) over 1e-06
FAILURE
'ERROR!

libswscale filter + flags (Match)

Using the libswscale library. Seems similar to colorspace, but with image resizing, and levels built in. This also has a number of libswscale parameters. Looking at the oiio difference, this is the first one that has an identical result to the input image.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=tv:out_color_matrix=bt709"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=tv:out_color_matrix=bt709" -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/spline444out_color_matrix.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444out_color_matrix.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444out_color_matrix.png"
Mean error = 0.00105769
RMS error = 0.00204785
Peak SNR = 53.774
Max error = 0.0078432 @ (1217, 1037, B) values are 0.294118, 0.294118, 0.745098 vs 0.294118, 0.298039, 0.752941
1276800 pixels (61.6%) over 1e-06
1276800 pixels (61.6%) over 1e-06
FAILURE
'ERROR!

libswscale filter + flags full-range (Match)

Using the libswscale library. Seems similar to colorspace, but with image resizing, and levels built in. This also has a number of libswscale parameters. Looking at the oiio difference, this is the first one that has an identical result to the input image.

ffmpeg flags to add: -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=full:out_color_matrix=bt709"

Full creation commandline:
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int+full_chroma_inp -vf "scale=in_range=full:in_color_matrix=bt709:out_range=full:out_color_matrix=bt709" -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range tv -colorspace bt709 -color_primaries bt709 -color_trc iec61966-2-1 ./chip-chart-yuvconvert/spline444out_color_matrixfull.mp4

OIIO idiff output

idiff -o ./chip-chart-yuvconvert/chip-chart-1080-noiccdiff.png ../sourceimages/chip-chart-1080-noicc.png ./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444out_color_matrixfull.png b'Comparing "../sourceimages/chip-chart-1080-noicc.png" and "./chip-chart-yuvconvert/chip-chart-1080-noicc-spline444out_color_matrixfull.png"
Mean error = 0.0193162
RMS error = 0.0297635
Peak SNR = 30.5263
Max error = 0.0823529 @ (578, 961, R) values are 0.905882, 0.905882, 0.933333 vs 0.988235, 0.984314, 1
1972990 pixels (95.1%) over 1e-06
1972990 pixels (95.1%) over 1e-06
FAILURE
'ERROR!