wiki:colorspace

Colorspace support in FFmpeg

What is colorspace? Why should we care?

Colorspace describes how an array of pixel values should be displayed on the screen. It provides information like how pixel values are stored within a file, and what the range and meaning of those values are.

Basically, it tells the format of the array of pixels (e.g. RGB or YUV), and how the values of each color component should be translated, to be properly displayed by the photons of the screen. (i.e. picking a colorspace randomly seems unlikely to be a good choice...)

The differences between RGB and YUV:

  • RGB distinguishes color pixel values into 3 components: Red, Green, Blue. (hence the name)
  • YUV uses a different representation schema that represents color pixel values in: Luma (Y, or brightness), Chroma (U and V, two color differences). This format exploits the fact that humans are able to better notice details in luminance (approximated by luma) than in chroma. [ Note: YUV represents color in 3 components. ]

Note:
͏    The term "YUV" is ambiguous and often used wrongly [1], including the definition of pixel formats in FFmpeg.
͏    A more accurate term for how colors stored in digital video would be ​YCbCr.
͏    Y'UV on the other hand specifies a colorspace consisting of luma (Y') and chrominance (UV) components.
͏    For more info read Wikipedia ​<YUV>.
[ [1]
͏    There's no practical difference between YUV and YCbCr: sort of more like "RGB" and "BGR".
͏    "UV" doesn't explicitly state the exact type of color difference neither. (so it might be "CbCr") ]

͏    In following, the term YUV is used as in FFmpeg pixel formats: referring to YCbCr in digital video.

The conversion between YUV pixel buffer representation and its visual representation depends on the type of the YUV represented in the pixel buffers, which are essentially device-dependent. The accuracy of grey vs color separation depends on how well the transformation matrix matches the underlying RGB space.

Examples are:

These standards describe not just things like how to convert a YUV signal to RGB, but also how a RGB signal should be represented in terms of photon emission, in a device-independent way.

How does FFmpeg identify colorspaces?

In FFmpeg, colorspaces are represented in the form of ​pixel format.

In practical terms, the properties you care about are:

  1. The signal format in the pixel buffer:
    1. the signal type: RGB, YUV, or other type, and
    2. the signal bit-depth.
  2. For YUV signals, the color range: full/pc/jpeg or limited/restricted/tv/mpeg. [ See also: # ͏"color_primaries" ]
    For 8bpc (bit-per-component): full means 0 .. 255, limited 16 .. 235.
  3. The transformation matrix between YUV and RGB.
  4. The linearization function from RGB to a linear RGB signal.
  5. The conversion matrix between the linearized RGB and the device-independent XYZ colorspace.

FFmpeg stores these properties in the AVFrame struct:

How to use FFmpeg to convert the colorspace

Warning: ​https://trac.ffmpeg.org/wiki/Scaling#Warning

Pixel format conversion is often performed by libswscale, which you will most likely access through the FFmpeg Scaler or the scale video filter.

Other video filters include:

Comparing and contrasting colorspace, colormatrix, libswscale, and zscale

  • colorspace and colormatrix can only convert YUV to YUV
  • libswscale can convert between YUV and RGB
  • colormatrix only supports 8bpc pixel formats
  • colorspace supports 8bpc, 10bpc, and 12bpc
  • colormatrix does not apply gamma and primaries correction (i.e. which exact color "red", "green", and "blue" each is)
  • colorspace applies gamma and primaries correction by default. (Use fast=1 to disable this for faster conversion or to make output compatible with output produced by colormatrix.)
  • colormatrix is C only, whereas colorspace uses x86 SIMD so it's faster
  • colormatrix produces horrible quality for 10bpc and 12bpc
  • colorspace produces something decent for 10bpc
  • For 8bpc, colorspace seems to produce slightly better quality than colormatrix
  • zscale produces better results at all bit depths

colorspace and friends

The easiest way to use these filters is to ensure that the input AVFrames have all relevant struct members set to the appropriate values. On ffmpeg command-line this is what options such as colorspace and color_trc do; you can also put them on the output side to modify what space the output is in.

If everything goes well, libswscale figures out how to do the conversion and you can avoid calling the filter manually. However, AVFrames does not cover every option needed, so advanced use will go back to colorspace or zscale.

See also sws_setColorspaceDetails() and ​F.X.'s colorspace answer.

sRGB

There is no colorspace default called sRGB in FFmpeg, because it's identical to BT.709 except for a different transfer function. Just use one of the following:

  • sRGB input, fast: -vf "colorspace=all=bt709:fast=1", aka -colorspace bt709 (on the input side!)
  • sRGB input, accurate: -vf "colorspace=all=bt709:itrc=srgb:fast=0", aka -colorspace bt709 -color_trc srgb (on the input side!)

See also ​F.X.'s HDR answer and ​Gyan's sRGB output answer. If srgb does not work, try the more academic name iec61966-2-1.

"color_primaries"

͏    Quick reference for somewhat cryptic "color_primaries" names:
͏    1: "bt709" (BT.709)
͏    5: "bt470bg" / "gamma28" (BT.470 BG)
͏    6: "smpte170m" (SMPTE 170 M)
͏    (alike for "colorspace" "color_trc")
͏    .
͏    See also:
(`ffmpeg -h full` derived)
[[ 

-color_range <int>  color range (from 0 to INT_MAX) (default unknown)
  0 unknown          Unspecified
    unspecified
  1 tv               MPEG (( 219 * 2^( n - 8 ) ))
    mpeg
    limited
  2 pc               JPEG (( 2^n - 1 ))
    jpeg
    full

-colorspace <int>      color space (from 0 to INT_MAX) (default unknown)
   0 rgb                RGB
   1 bt709              BT.709
   2 unknown            Unspecified
     unspecified
   4 fcc                FCC
   5 bt470bg            BT.470 BG
   6 smpte170m          SMPTE 170 M
   7 smpte240m          SMPTE 240 M
   8 ycgco              YCGCO
     ycocg
   9 bt2020nc           BT.2020 NCL
     bt2020_ncl
  10 bt2020c            BT.2020 CL
     bt2020_cl
  11 smpte2085          SMPTE 2085
  12 chroma-derived-nc  Chroma-derived NCL
  13 chroma-derived-c   Chroma-derived CL
  14 ictcp              ICtCp
  15 ipt-c2             IPT-C2
  16 ycgco-re           YCGCO-R (even add)
  17 ycgco-ro           YCGCO-R (odd add)

-color_primaries <int>  color primaries (from 1 to INT_MAX) (default unknown)
   1 bt709               BT.709
   2 unknown             Unspecified
     unspecified
   4 bt470m              BT.470 M
   5 bt470bg             BT.470 BG
   6 smpte170m           SMPTE 170 M
   7 smpte240m           SMPTE 240 M
   8 film                Film
   9 bt2020              BT.2020
  10 smpte428            SMPTE 428-1
     smpte428_1
  11 smpte431            SMPTE 431-2
  12 smpte432            SMPTE 422-1
  22 jedec-p22           JEDEC P22
     ebu3213             EBU 3213-E

-color_trc <int>  color transfer characteristics (from 1 to INT_MAX) (default unknown)
   1 bt709         BT.709
   2 unknown       Unspecified
     unspecified
   4 gamma22       BT.470 M
   5 gamma28       BT.470 BG
   6 smpte170m     SMPTE 170 M
   7 smpte240m     SMPTE 240 M
   8 linear        Linear
   9 log100        Log
     log
  10 log316        Log square root
     log_sqrt
  11 iec61966-2-4  IEC 61966-2-4
     iec61966_2_4
  12 bt1361e       BT.1361
     bt1361
  13 iec61966-2-1  IEC 61966-2-1
     iec61966_2_1
  14 bt2020-10     BT.2020 10-bit
     bt2020_10bit
  15 bt2020-12     BT.2020 12-bit
     bt2020_12bit
  16 smpte2084     SMPTE 2084
  17 smpte428      SMPTE 428-1
     smpte428_1
  18 arib-std-b67  ARIB STD-B67

]]
͏    [ Still cryptic whatsoever... ]

Examples (with 20240506 git-master)

͏    Caveat: ​https://trac.ffmpeg.org/ticket/11238#comment:5

͏    Note:
͏    Use [ ​https://github.com/MasterInQuestion/Markup/blob/main/picdif.htm ] for image comparison.
͏    (may not work well on small screen and/or browser asserted ​͏"devicePixelRatio" != 1)
͏    .
͏    Image comparison also by:
͏    ffmpeg -hide_banner -nostdin -i ${in0} -i ${in1} -lavfi "ssim; [0][1]psnr" -f null -
͏    [ ​https://trac.ffmpeg.org/ticket/10922#comment:description ]

͏    Warning:
͏    Due to TracWiki's limitation, the page is riddled with Unicode special characters (to workaround).
͏    (either invisible or of tricky look; near links, indentation; maybe else)
͏    .
͏    Copy / Edit with caution.


͏    Some changes occurred for the ͏"colorspace" filter meanwhile.
͏    Differ the following 4:
͏    #colorspace_yuv444p10le-yuv444p
͏    #colorspace_fast=0_iall=bt601-6-625
͏    #colorspace_fast=0_iall=bt601-6-525
͏    #colorspace_yuv420p10le-yuv420p

͏    Common pattern:
͏    "-vf" involved either:
͏    |1| "colorspace=bt709:iall=bt601-6-625:fast=1"
͏    |2| "colorspace=bt709:iall=bt601-6-625"
͏    |3| "colorspace=bt709:iall=bt601-6-525"

͏    Rather noticeable visual difference for |2| |3|. [ Near right-upper houses/shrubs in dark. ]
͏    Clarification appreciated. [ Rationale and relevant commits? ]
͏    .
͏    Warning message of interest:
͏    “[Parsed_colorspace_0] Input range not set, assuming tv/mepg”
͏    Specifying "irange=2" white-out things. (assumed 1 when not set)
͏    Note 6.1.1 didn't emit the warning: but generated [near-]identical [1] files as 20240506 git-master.
͏    .
͏    Less noticeable for |1|: mostly noise differences. [ Near aforementioned area; and the sky banding. ]

[ [1]
͏    "fast=1" related ones differ petty noises:
͏    Presumably for the added "csp:bt709 range:tv" assertions.

͏    Caveat the execution may have platform dependent differences. (typically no matter)
͏    "+bitexact" to various flags (͏"-sws_flags", ͏"-flags", ͏"-fflags") to insist platform independent (also non-stochastic) output. (may sacrifice speed)
͏    [ ^ One would also typically like "-map_metadata -1 -map_chapters -1" in such case. ]

͏    "-bitexact" should be shortcut for above:
͏    ​https://github.com/search?type=code&q=repo:FFmpeg/FFmpeg+path:/^fftools%5C//+/(?-i)BITEXACT/
͏    (seemingly missing "SWS_BITEXACT" yet) [ #11007 ] ]


The input source (rgb24):

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/origin(rgb24).webp
(~ 879.32 KiB; WebP Lossless: 1440x836)


"colormatrix" (yuv444p10le):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colormatrix_yuv444p10le.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colormatrix_yuv444p10le.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colormatrix_yuv444p10le.webp"

Output bit-identical as "colormatrix" (yuv444p).

"colorspace" (yuv444p10le):

[ Note:
͏    SSIM > 99.98% with The input source (rgb24).
͏    Should be 100% if the conversion algorithms are improved, though. ]

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv444p10le.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv444p10le.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv444p10le.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv444p10le.webp


Reference (yuv444p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 5 -color_primaries 5 -color_trc 6 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "yuv444p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "yuv444p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "yuv444p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/yuv444p.webp

"colormatrix" (yuv444p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colormatrix_yuv444p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colormatrix_yuv444p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colormatrix_yuv444p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colormatrix_yuv444p.webp

"colorspace" (yuv444p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv444p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv444p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv444p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv444p.webp

"colorspace" (yuv444p10le -> yuv444p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "colorspace_yuv444p10le.avi" -pix_fmt yuv444p -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv444p10le-yuv444p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv444p10le-yuv444p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv444p10le-yuv444p.webp"

͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv444p10le-yuv444p.webp
͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv444p10le-yuv444p.20190416.webp


"colorspace" with "fast=0" "iall=bt601-6-625":

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_fast=0_iall=bt601-6-625.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_fast=0_iall=bt601-6-625.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_fast=0_iall=bt601-6-625.webp"

͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_fast=0_iall=bt601-6-625.webp
͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_fast=0_iall=bt601-6-625.20190416.webp

"colorspace" with "fast=0" "iall=bt601-6-525":

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-525" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_fast=0_iall=bt601-6-525.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_fast=0_iall=bt601-6-525.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_fast=0_iall=bt601-6-525.webp"

͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_fast=0_iall=bt601-6-525.webp
͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_fast=0_iall=bt601-6-525.20190416.webp

"colorspace" with "fast=1" "iall=bt601-6-525":

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-525:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_fast=1_iall=bt601-6-525.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_fast=1_iall=bt601-6-525.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_fast=1_iall=bt601-6-525.webp"

Output bit-identical as "colorspace" (yuv444p10le).




Reference (yuv420p10le):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv420p10le -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 5 -color_primaries 5 -color_trc 6 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "yuv420p10le.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "yuv420p10le.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "yuv420p10le.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/yuv420p10le.webp

"colorspace" (yuv420p10le):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv420p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv420p10le.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv420p10le.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv420p10le.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv420p10le.webp


Reference (yuv420p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv420p -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 5 -color_primaries 5 -color_trc 6 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "yuv420p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "yuv420p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "yuv420p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/yuv420p.webp

"colorspace" (yuv420p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "origin(rgb24).webp" -pix_fmt yuv420p -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv420p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv420p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv420p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv420p.webp

"colorspace" (yuv420p10le -> yuv420p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "colorspace_yuv420p10le.avi" -pix_fmt yuv420p -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv420p10le-yuv420p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv420p10le-yuv420p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv420p10le-yuv420p.webp"

͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv420p10le-yuv420p.webp
͏    ​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv420p10le-yuv420p.20190416.webp

"colorspace" (yuv444p10le -> yuv420p):

͏    ffmpeg -y -v trace -hide_banner -nostdin -nostats -i "colorspace_yuv444p10le.avi" -pix_fmt yuv420p -sws_flags spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" "colorspace_yuv444p10le-yuv420p.avi"
͏    ffmpeg -y -v debug -hide_banner -nostdin -nostats -i "colorspace_yuv444p10le-yuv420p.avi" -pix_fmt rgb24 -sws_flags +accurate_rnd+full_chroma_int -lossless 1 -q 100 -compression_level 6 "colorspace_yuv444p10le-yuv420p.webp"

​https://github.com/MasterInQuestion/attach/raw/main/@ext/trac.ffmpeg.org/wiki/colorspace/colorspace_yuv444p10le-yuv420p.webp

"full_chroma_in*" related

[ haasn @ CE 2024-08-16 09:43:37 UTC:
​https://github.com/FFmpeg/FFmpeg/commit/3e064f52eb368a373ded6e3704fcf29f1db3ff12

[ "SWS_FULL_CHR_H_INT"
͏    Perform full chroma upsampling when upscaling to RGB.

͏    For example, when converting 50x50 yuv420p to 100x100 rgba:
͏    Setting this flag will scale the chroma plane from 25x25 to 100x100 (4:4:4):
͏    And then convert the 100x100 yuv444p image to rgba in the final output step.
͏    .
͏    Without this flag, the chroma plane is instead scaled to 50x100 (4:2:2):
͏    With a single chroma sample being re-used, for both of the horizontally adjacent RGBA output pixels. ]

[ "SWS_FULL_CHR_H_INP"
͏    Perform full chroma interpolation when downscaling RGB sources.

͏    For example, when converting a 100x100 rgba source to 50x50 yuv444p:
͏    Setting this flag will generate a 100x100 (4:4:4) chroma plane, which is then downscaled to the required 50x50.
͏    .
͏    Without this flag, the chroma plane is instead generated at 50x100 (dropping every other pixel):
͏    Before then being downscaled to the required 50x50 resolution. ] ]

͏----

[ MasterQuestionable:
͏    The description is much misleading... if not outright misinformation?
͏    |1| Both may be RGB irrelevant: occurs during YUV unsubsampling.
͏    |2| SWS_FULL_CHR_H_INT may involve down-scaling too.
͏    |3| [
͏    SWS_FULL_CHR_H_INP asserts full-chroma input; which then forces use of full-chroma interpolation: whether sensible or not.
͏    Which is actually somewhat useless: as the default handling seems... sensible? ]

͏    Hint about ͏"full_chroma_inp":
͏    ​https://github.com/search?type=code&q=repo:FFmpeg/FFmpeg+%22SWS_FULL_CHR_H_INP%22
͏    ​https://github.com/FFmpeg/FFmpeg/blob/271aea60a4cd211d92923c53b72cd074c3030897/libswscale/utils.c#L1540-L1556
͏    ​https://github.com/FFmpeg/FFmpeg/blob/41ed7ab45fc693f7d7fc35664c0233f4c32d69bb/doc/swscale.txt#L50-L57

͏    On "full_chroma_int":
͏    ​https://github.com/MasterInQuestion/attach/commit/e18e5cd26b9d27bacefa685ba70d0d41bc7d7cbc#diff-75a0130f1814ba26c23e3a6fc6ce5046620163061d392086bc55e2c13c145bf9L264 ]

Last modified 5 weeks ago Last modified on Nov 19, 2024, 11:01:35 PM

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