Colour of video changes when using FFMPEG with AVS Script

[bradwiggo]

If I run an AVS script using FFMPEG, there will' be a slight change to the overall colour of the video. This does not happening using VirtualDub(2), with default settings and x264 8 bit encoder.

This is the ffmpeg command:

ffmpeg.exe -i test.avs -crf 16 "%%~F.mp4"

Does anybody know how to fix this? I had this issue before with hybrid and it ended up being VUI settings, idk if that's even a thing with FFMPEG though (only reason I'm using FFMPEG is I have about 100 AVS files to process so need something automatic).

(I didn't post the AVS script as it works fine in virtualdub, so presumably it has nothing to do with the script, but rather the encoder. If seeing the script would be useful I can post it though)

[poisondeathray]

You can set the VUI settings with ffmpeg too.

What is the colorspace or output of the avs script ? YUV 4:2:0 (YV12) ? RGB ? Something else?. Post your script

How are you determining the "color" ? What are you using to view ?

[bradwiggo]

You can set the VUI settings with ffmpeg too.

What is the colorspace or output of the avs script ? YUV 4:2:0 (YV12) ? RGB ? Something else?. Post your script

How are you determining the "color" ? What are you using to view ?

LWLibavVideoSource("C:\Users\ME\Documents\Video Processing\test.mkv")
#ConvertToYV24()
nnedi3_rpow2(2, cshift="LanczosResize", fwidth=720, fheight=404)
aWarpSharp2(depth=3)
Sharpen(0.3)
nnedi3_rpow2(2, cshift="LanczosResize", fwidth=1280, fheight=718)
aWarpSharp2(depth=5)
Sharpen(0.5)
#ConvertToYV12()

(commented or uncommented the YV ones, doesn't make a difference)

Input Video:

General
Unique ID                                : 152948037013579271062902687678894660881 (0x7310B86EE28BA6AA2B942790AC3B5D11)
Complete name                            : C:\Users\bradw\Documents\Video Processing\test.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 514 KiB
Duration                                 : 6 s 465 ms
Overall bit rate                         : 651 kb/s
Writing application                      : Lavf58.29.100
Writing library                          : Lavf58.29.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3
Format settings                          : CABAC / 5 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 5 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 6 s 465 ms
Width                                    : 720 pixels
Height                                   : 404 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (23976/1000) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Writing library                          : x264 core 125 r2200 999b753
Encoding settings                        : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=crf / mbtree=1 / crf=26.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Default                                  : Yes
Forced                                   : No

Output of FFMPEG (wrong colour):

General
Unique ID                                : 222650574584730242227513090272354369807 (0xA780F0DD09C8BCB89E12964A1850010F)
Complete name                            : C:\Users\bradw\Documents\Video Processing\Z20 no yv.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 1.78 MiB
Duration                                 : 6 s 465 ms
Overall bit rate                         : 2 310 kb/s
Writing application                      : Lavf59.3.100
Writing library                          : Lavf59.3.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 6 s 465 ms
Bit rate                                 : 2 264 kb/s
Width                                    : 1 280 pixels
Height                                   : 718 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (23976/1000) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.103
Stream size                              : 1.74 MiB (98%)
Writing library                          : x264 core 164 r3065 ae03d92
Encoding settings                        : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=9 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=20.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Default                                  : Yes
Forced                                   : No

Output of VirtualDub (correct colour):

General
Unique ID                                : 244083759067673380596137552171647956075 (0xB7A0D2720BC3B0AC461BC8978C78F46B)
Complete name                            : C:\Users\bradw\Documents\Video Processing\dub.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 1.72 MiB
Duration                                 : 6 s 548 ms
Overall bit rate                         : 2 208 kb/s
Writing application                      : Lavf57.79.100
Writing library                          : Lavf57.79.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 6 s 465 ms
Bit rate                                 : 2 164 kb/s
Width                                    : 1 280 pixels
Height                                   : 718 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (23976/1000) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.098
Stream size                              : 1.67 MiB (97%)
Writing library                          : x264 core 157 r2935M 545de2f
Encoding settings                        : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=9 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=20.3 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Matrix coefficients                      : BT.470 System B/G

Determining colour just by looking at it, the one that changes is lighter and brighter I would say I guess. Using MPC-HC, just alt tabbing between two different fullscreen windows to see difference.

[poisondeathray]

Determining colour just by looking at it, the one that changes is lighter and brighter I would say I guess. Using MPC-HC, just alt tabbing between two different fullscreen windows to see difference.

1) If you use 2 instances of software players, often they might be using different renders. eg. One might be EVR, one might be using MadVR or Overlay or etc.... This can result in vastly different brightness and colors.



2) Usually when you upscale, you perform a 601=>709 matrix conversion, and flag it as 709 because:

2a) many players and devices ignore flags and determine color by height. For "SD" they use 601, for "HD" they use 709
2b) but some pay attention to flags in order of priority, then by height, otherwise 601.

So doing both covers practically all cases. Also, by convention "HD" uses 709. 99.9% of commercial and consumer HD sources use 709, so it's the "right" thing to do and expected

In the script

ColorMatrix(mode="rec.601->rec.709", clamp=0)

To flag it as 709 for ffmpeg libx264

-x264opts colormatrix=bt709

Note the vdub case is flagged as BT.470, so that's technically correct - it's the "wrong" color for HD, but your source wasn't changed to 709 color (ie the flag is correct for the video). Some players will ignore the flag and play it as 709 and the colors will look incorrect. But some will pay attention to the flag, and the colors will look correct. (I'd rather have it correct in both cases, not just some of the time)

[bradwiggo]

Determining colour just by looking at it, the one that changes is lighter and brighter I would say I guess. Using MPC-HC, just alt tabbing between two different fullscreen windows to see difference.

1) If you use 2 instances of software players, often they might be using different renders. eg. One might be EVR, one might be using MadVR or Overlay or etc.... This can result in vastly different brightness and colors.



2) Usually when you upscale, you perform a 601=>709 matrix conversion, and flag it as 709 because:

2a) many players and devices ignore flags and determine color by height. For "SD" they use 601, for "HD" they use 709
2b) but some pay attention to flags in order of priority, then by height, otherwise 601.

So doing both covers practically all cases. Also, by convention "HD" uses 709. 99.9% of commercial and consumer HD sources use 709, so it's the "right" thing to do and expected

In the script

ColorMatrix(mode="rec.601->rec.709", clamp=0)

To flag it as 709 for ffmpeg libx264

-x264opts colormatrix=bt709

Note the vdub case is flagged as BT.470, so that's technically correct - it's the "wrong" color for HD, but your source wasn't changed to 709 color (ie the flag is correct for the video). Some players will ignore the flag and play it as 709 and the colors will look incorrect. But some will pay attention to the flag, and the colors will look correct. (I'd rather have it correct in both cases, not just some of the time)

Thanks, adding those to the file and command line worked! Where is the best place to add the line to the AVS script? I will have to uncomment the "convert to yvXX" lines as they are needed for some of the files (some of them don't have "mod 4" dimensions or something. Would it be best to add the colourmatrix command at the very end after all other lines?

[hello_hello]

Try HDRMatrix. https://www.videoartifact.com/hdr/
I'm pretty sure it supports all YUV formats except for YUY2.

Matrix(From=601, To=709)

It seems to be better in respect to not causing any color banding, compared to ColorMatrix (not that ColorMatrix is bad).

I tend to convert the colors before resizing (when upscaling) as I guess it should be faster than doing it after upscaling, but in practice I don't think it matters.

As a side note, this might save you having to do convert to YV24 and back.

function CropMod4Width(clip Source)   {

ModFourWidth = \
(((FindStr(LCase(VersionString()), "avisynth+") > 0) || (FindStr(LCase(VersionString()), "avisynth neo") > 0)) && \
(Is420(Source) || Is422(Source))) || IsYV12(Source) || IsYV16(Source) || IsYUY2(Source) || IsYV411(Source)

return !ModFourWidth ? Source : (width(Source) % 4 == 0) ? Source : Source.Crop(2,0,0,0)   }

It just crops a couple of pixels from the left side to make the width mod4 for formats that require it to keep nnedi3 happy. If mod4 isn't required or the width is already mod4, it does nothing. Insert it in the script before nnedi3.

CropMod4Width()
nnedi3_rpow2(2, cshift="LanczosResize", fwidth=720, fheight=404)