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)

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!