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[79.124.17.100]) by mx.google.com with ESMTP id c14-20020a170906d18e00b006df76385c2csi23595888ejz.204.2022.03.31.04.35.07; Thu, 31 Mar 2022 04:35:07 -0700 (PDT) Received-SPF: pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) client-ip=79.124.17.100; Authentication-Results: mx.google.com; dkim=neutral (body hash did not verify) header.i=@haasn.xyz header.s=mail header.b=MWu996GP; spf=pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) smtp.mailfrom=ffmpeg-devel-bounces@ffmpeg.org Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 49A9368B1E0; Thu, 31 Mar 2022 14:35:04 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from haasn.dev (haasn.dev [78.46.187.166]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 8947368AAD7 for ; Thu, 31 Mar 2022 14:34:57 +0300 (EEST) Received: from haasn.dev (unknown [10.30.0.2]) by haasn.dev (Postfix) with ESMTP id 402CE49C15; Thu, 31 Mar 2022 13:34:57 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=haasn.xyz; s=mail; t=1648726497; bh=c8pUNeFxKAukbDOn1sr3dFtyGGdxqMaAH+sHJdAqtjk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MWu996GPMAXx+kuB+FA3mJYE504j6rs2FYibeCP3vMK3YRod8NhVJSbUe8W2f7Hlc 9ZBHl8LOXMqFKCJDAEOg+F40upeTRrlWc7Cej5nsKHLl/jb02TWCdcjp1zSAEKYMEn 2/DQI7boiCylhgPba8c9vfoC1m+0ONig7I0pxSJ0= From: Niklas Haas To: ffmpeg-devel@ffmpeg.org Date: Thu, 31 Mar 2022 13:34:30 +0200 Message-Id: <20220331113429.125261-1-ffmpeg@haasn.xyz> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220329121327.48924-1-ffmpeg@haasn.xyz> References: <20220329121327.48924-1-ffmpeg@haasn.xyz> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH v2] doc/filters: document vf_libplacebo X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Niklas Haas Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" X-TUID: ZTL7wyhjuVfm From: Niklas Haas Signed-off-by: Niklas Haas --- Changes in v2: - expand documentation of tone mapping curves - slight rewording of some sections - add more examples --- doc/filters.texi | 494 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 494 insertions(+) diff --git a/doc/filters.texi b/doc/filters.texi index 1d56d24819..a6f2f1397e 100644 --- a/doc/filters.texi +++ b/doc/filters.texi @@ -14793,6 +14793,500 @@ ffmpeg -i input.mov -vf lensfun=make=Canon:model="Canon EOS 100D":lens_model="Ca @end itemize +@section libplacebo + +Flexible GPU-accelerated processing filter based on libplacebo +(@url{https://code.videolan.org/videolan/libplacebo}). Note that this filter +currently only accepts Vulkan input frames. + +@subsection Options + +The options for this filter are divided into the following sections: + +@subsubsection Output mode +These options control the overall output mode. By default, libplacebo will try +to preserve the source colorimetry and size as best as it can, but it will +apply any embedded film grain, dolby vision metadata or anamorphic SAR present +in source frames. +@table @option +@item w +@item h +Set the output video dimension expression. Default value is the input dimension. + +Allows for the same expressions as the @ref{scale} filter. + +@item format +Set the output format override. If unset (the default), frames will be output +in the same format as the respective input frames. Otherwise, format conversion +will be performed. + +@item force_original_aspect_ratio +@item force_divisible_by +Work the same as the identical @ref{scale} filter options. + +@item normalize_sar +If enabled (the default), output frames will always have a pixel aspect ratio +of 1:1. If disabled, any aspect ratio mismatches, including those from e.g. +anamorphic video sources, are forwarded to the output pixel aspect ratio. + +@item pad_crop_ratio +Specifies a ratio (between @code{0.0} and @code{1.0}) between padding and +cropping when the input aspect ratio does not match the output aspect ratio and +@option{normalize_sar} is in effect. The default of @code{0.0} always pads the +content with black borders, while a value of @code{1.0} always crops off parts +of the content. Intermediate values are possible, leading to a mix of the two +approaches. + +@item colorspace +@item color_primaries +@item color_trc +@item range +Configure the colorspace that output frames will be delivered in. The default +value of @code{auto} outputs frames in the same format as the input frames, +leading to no change. For any other value, conversion will be performed. + +See the @ref{setparams} filter for a list of possible values. + +@item apply_filmgrain +Apply film grain (e.g. AV1 or H.274) if present in source frames, and strip +it from the output. Enabled by default. + +@item apply_dolbyvision +Apply Dolby Vision RPU metadata if present in source frames, and strip it from +the output. Enabled by default. Note that Dolby Vision will always output +BT.2020+PQ, overriding the usual input frame metadata. These will also be +picked as the values of @code{auto} for the respective frame output options. +@end table + +@subsubsection Scaling +The options in this section control how libplacebo performs upscaling and (if +necessary) downscaling. Note that libplacebo will always internally operate on +4:4:4 content, so any sub-sampled chroma formats such as @code{yuv420p} will +necessarily be upsampled and downsampled as part of the rendering process. That +means scaling might be in effect even if the source and destination resolution +are the same. +@table @option +@item upscaler +@item downscaler +Configure the filter kernel used for upscaling and downscaling. The respective +defaults are @code{spline36} and @code{mitchell}. For a full list of possible +values, pass @code{help} to these options. The most important values are: +@table @samp + +@item none +Forces the use of built-in GPU texture sampling (typically bilinear). Extremely +fast but poor quality, especially when downscaling. + +@item bilinear +Bilinear interpolation. Can generally be done for free on GPUs, except when +doing so would lead to aliasing. Fast and low quality. + +@item nearest +Nearest-neighbour interpolation. Sharp but highly aliasing. + +@item oversample +Algorithm that looks visually similar to nearest-neighbour interpolation but +tries to preserve pixel aspect ratio. Good for pixel art, since it results in +minimal distortion of the artistic appearance. + +@item lanczos +Standard sinc-sinc interpolation kernel. + +@item spline36 +Cubic spline approximation of lanczos. No difference in performance, but has +very slightly less ringing. + +@item ewa_lanczos +Elliptically weighted average version of lanczos, based on a jinc-sinc kernel. +This is also popularly referred to as just "Jinc scaling". Slow but very high +quality. + +@item gaussian +Gaussian kernel. Has certain ideal mathematical properties, but subjectively +very blurry. + +@item mitchell +Cubic BC spline with parameters recommended by Mitchell and Netravali. Very +little ringing. +@end table + +@item lut_entries +Configures the size of scaler LUTs, ranging from @code{1} to @code{256}. The +default of @code{0} will pick libplacebo's internal default, typically +@code{64}. + +@item antiringing +Enables anti-ringing (for non-EWA filters). The value (between @code{0.0} and +@code{1.0}) configures the strength of the anti-ringing algorithm. May increase +aliasing if set too high. Disabled by default. + +@item sigmoid +Enable sigmoidal compression during upscaling. Reduces ringing slightly. +Enabled by default. +@end table + +@subsubsection Debanding +Libplacebo comes with a built-in debanding filter that is good at counteracting +many common sources of banding and blocking. Turning this on is highly +recommended whenever quality is desired. +@table @option +@item deband +Enable (fast) debanding algorithm. Disabled by default. + +@item deband_iterations +Number of deband iterations of the debanding algorithm. Each iteration is +performed with progressively increased radius (and diminished threshold). +Recommended values are in the range @code{1} to @code{4}. Defaults to @code{1}. + +@item deband_threshold +Debanding filter strength. Higher numbers lead to more aggressive debanding. +Defaults to @code{4.0}. + +@item deband_radius +Debanding filter radius. A higher radius is better for slow gradients, while +a lower radius is better for steep gradients. Defaults to @code{16.0}. + +@item deband_grain +Amount of extra output grain to add. Helps hide imperfections. Defaults to +@code{6.0}. +@end table + +@subsubsection Color adjustment +A collection of subjective color controls. Not very rigorous, so the exact +effect will vary somewhat depending on the input primaries and colorspace. +@table @option +@item brightness +Brightness boost, between @code{-1.0} and @code{1.0}. Defaults to @code{0.0}. + +@item contrast +Contrast gain, between @code{0.0} and @code{16.0}. Defaults to @code{1.0}. + +@item saturation +Saturation gain, between @code{0.0} and @code{16.0}. Defaults to @code{1.0}. + +@item hue +Hue shift in radians, between @code{-3.14} and @code{3.14}. Defaults to +@code{0.0}. This will rotate the UV subvector, defaulting to BT.709 +coefficients for RGB inputs. + +@item gamma +Gamma adjustment, between @code{0.0} and @code{16.0}. Defaults to @code{1.0}. + +@item cones +Cone model to use for color blindness simulation. Accepts any combination of +@code{l}, @code{m} and @code{s}. Here are some examples: +@table @samp +@item m +Deuteranomaly / deuteranopia (affecting 3%-4% of the population) +@item l +Protanomaly / protanopia (affecting 1%-2% of the population) +@item l+m +Monochromacy (very rare) +@item l+m+s +Achromatopsy (complete loss of daytime vision, extremely rare) +@end table + +@item cone-strength +Gain factor for the cones specified by @code{cones}, between @code{0.0} and +@code{10.0}. A value of @code{1.0} results in no change to color vision. A +value of @code{0.0} (the default) simulates complete loss of those cones. Values +above @code{1.0} result in exaggerating the differences between cones, which +may help compensate for reduced color vision. +@end table + +@subsubsection Peak detection +To help deal with sources that only have static HDR10 metadata (or no tagging +whatsoever), libplacebo uses its own internal frame analysis compute shader to +analyze source frames and adapt the tone mapping function in realtime. If this +is too slow, or if exactly reproducible frame-perfect results are needed, it's +recommended to turn this feature off. +@table @option +@item peak_detect +Enable HDR peak detection. Ignores static MaxCLL/MaxFALL values in favor of +dynamic detection from the input. Note that the detected values do not get +written back to the output frames, they merely guide the internal tone mapping +process. Enabled by default. + +@item smoothing_period +Peak detection smoothing period, between @code{0.0} and @code{1000.0}. Higher +values result in peak detection becoming less responsive to changes in the +input. Defaults to @code{100.0}. + +@item minimum_peak +Lower bound on the detected peak (relative to SDR white), between @code{0.0} +and @code{100.0}. Defaults to @code{1.0}. + +@item scene_threshold_low +@item scene_threshold_high +Lower and upper thresholds for scene change detection. Expressed in a +logarithmic scale between @code{0.0} and @code{100.0}. Default to @code{5.5} +and @code{10.0}, respectively. Setting either to a negative value disables +this functionality. + +@item overshoot +Peak smoothing overshoot margin, between @code{0.0} and @code{1.0}. Provides a +safety margin to prevent clipping as a result of peak smoothing. Defaults to +@code{0.05}, corresponding to a margin of 5%. +@end table + +@subsubsection Tone mapping +The options in this section control how libplacebo performs tone-mapping and +gamut-mapping when dealing with mismatches between wide-gamut or HDR content. +In general, libplacebo relies on accurate source tagging and mastering display +gamut information to produce the best results. +@table @option +@item intent +Rendering intent to use when adapting between different primary color gamuts +(after tone-mapping). +@table @samp +@item perceptual +Perceptual gamut mapping. Currently equivalent to relative colorimetric. +@item relative +Relative colorimetric. This is the default. +@item absolute +Absolute colorimetric. +@item saturation +Saturation mapping. Forcibly stretches the source gamut to the target gamut. +@end table + +@item gamut_mode +How to handle out-of-gamut colors that can occur as a result of colorimetric +gamut mapping. +@table @samp +@item clip +Do nothing, simply clip out-of-range colors to the RGB volume. This is the +default. +@item warn +Highlight out-of-gamut pixels (by coloring them pink). +@item darken +Linearly reduces content brightness to preserves saturated details, followed by +clipping the remaining out-of-gamut colors. As the name implies, this makes +everything darker, but provides a good balance between preserving details and +colors. +@item desaturate +Hard-desaturates out-of-gamut colors towards white, while preserving the +luminance. Has a tendency to shift colors. +@end table + +@item tonemapping +Tone-mapping algorithm to use. Available values are: +@table @samp +@item auto +Automatic selection based on internal heuristics. This is the default. +@item clip +Performs no tone-mapping, just clips out-of-range colors. Retains perfect color +accuracy for in-range colors but completely destroys out-of-range information. +Does not perform any black point adaptation. Not configurable. +@item bt.2390 +EETF from the ITU-R Report BT.2390, a hermite spline roll-off with linear +segment. The knee point offset is configurable. Note that this parameter +defaults to @code{1.0}, rather than the value of @code{0.5} from the ITU-R +spec. +@item bt.2446a +EETF from ITU-R Report BT.2446, method A. Designed for well-mastered HDR +sources. Can be used for both forward and inverse tone mapping. Not +configurable. +@item spline +Simple spline consisting of two polynomials, joined by a single pivot point. +The parameter gives the pivot point (in PQ space), defaulting to @code{0.30}. +Can be used for both forward and inverse tone mapping. +@item reinhard +Simple non-linear, global tone mapping algorithm. The parameter specifies the +local contrast coefficient at the display peak. Essentially, a parameter of +@code{0.5} implies that the reference white will be about half as bright as +when clipping. Defaults to @code{0.5}, which results in the simplest +formulation of this function. +@item mobius +Generalization of the reinhard tone mapping algorithm to support an additional +linear slope near black. The tone mapping parameter indicates the trade-off +between the linear section and the non-linear section. Essentially, for a given +parameter @var{x}, every color value below @var{x} will be mapped linearly, +while higher values get non-linearly tone-mapped. Values near @code{1.0} make +this curve behave like @code{clip}, while values near @code{0.0} make this +curve behave like @code{reinhard}. The default value is @code{0.3}, which +provides a good balance between colorimetric accuracy and preserving +out-of-gamut details. +@item hable +Piece-wise, filmic tone-mapping algorithm developed by John Hable for use in +Uncharted 2, inspired by a similar tone-mapping algorithm used by Kodak. +Popularized by its use in video games with HDR rendering. Preserves both dark +and bright details very well, but comes with the drawback of changing the +average brightness quite significantly. This is sort of similar to +@code{reinhard} with parameter @code{0.24}. +@item gamma +Fits a gamma (power) function to transfer between the source and target color +spaces, effectively resulting in a perceptual hard-knee joining two roughly +linear sections. This preserves details at all scales fairly accurately, but +can result in an image with a muted or dull appearance. The parameter is used +as the cutoff point, defaulting to @code{0.5}. +@item linear +Linearly stretches the input range to the output range, in PQ space. This will +preserve all details accurately, but results in a significantly different +average brightness. Can be used for inverse tone-mapping in addition to regular +tone-mapping. The parameter can be used as an additional linear gain +coefficient (defaulting to @code{1.0}). +@end table + +@item tonemapping_param +For tunable tone mapping functions, this parameter can be used to fine-tune the +curve behavior. Refer to the documentation of @code{tonemapping}. The default +value of @code{0.0} is replaced by the curve's preferred default setting. + +@item tonemapping_mode +This option determines how the tone mapping function specified by +@code{tonemapping} is applied to the colors in a scene. Possible values are: +@table @samp +@item auto +Automatic selection based on internal heuristics. This is the default. +@item rgb +Apply the function per-channel in the RGB colorspace. +Per-channel tone-mapping in RGB. Guarantees no clipping and heavily desaturates +the output, but distorts the colors quite significantly. Very similar to the +"Hollywood" look and feel. +@item max +Tone-mapping is performed on the brightest component found in the signal. Good +at preserving details in highlights, but has a tendency to crush blacks. +@item hybrid +Tone-map per-channel for highlights and linearly (luma-based) for +midtones/shadows, based on a fixed gamma @code{2.4} coefficient curve. +@item luma +Tone-map linearly on the luma component (CIE Y), and adjust (desaturate) the +chromaticities to compensate using a simple constant factor. This is +essentially the mode used in ITU-R BT.2446 method A. +@end table + +@item inverse_tonemapping +If enabled, this filter will also attempt stretching SDR signals to fill HDR +output color volumes. Disabled by default. + +@item tonemapping_crosstalk +Extra tone-mapping crosstalk factor, between @code{0.0} and @code{0.3}. This +can help reduce issues tone-mapping certain bright spectral colors. Defaults to +@code{0.04}. + +@item tonemapping_lut_size +Size of the tone-mapping LUT, between @code{2} and @code{1024}. Defaults to +@code{256}. Note that this figure is squared when combined with +@code{peak_detect}. +@end table + +@subsubsection Dithering +By default, libplacebo will dither whenever necessary, which includes rendering +to any integer format below 16-bit precision. It's recommended to always leave +this on, since not doing so may result in visible banding in the output, even +if the @code{debanding} filter is enabled. If maximum performance is needed, +use @code{ordered_fixed} instead of disabling dithering. +@table @option +@item dithering +Dithering method to use. Accepts the following values: +@table @samp +@item none +Disables dithering completely. May result in visible banding. +@item blue +Dither with pseudo-blue noise. This is the default. +@item ordered +Tunable ordered dither pattern. +@item ordered_fixed +Faster ordered dither with a fixed size of @code{6}. Texture-less. +@item white +Dither with white noise. Texture-less. +@end table + +@item dither_lut_size +Dither LUT size, as log base2 between @code{1} and @code{8}. Defaults to +@code{6}, corresponding to a LUT size of @code{64x64}. + +@item dither_temporal +Enables temporal dithering. Disabled by default. +@end table + +@subsubsection Custom shaders +libplacebo supports a number of custom shaders based on the mpv .hook GLSL +syntax. A collection of such shaders can be found here: +@url{https://github.com/mpv-player/mpv/wiki/User-Scripts#user-shaders} + +A full description of the mpv shader format is beyond the scope of this +section, but a summary can be found here: +@url{https://mpv.io/manual/master/#options-glsl-shader} +@table @option +@item custom_shader_path +Specifies a path to a custom shader file to load at runtime. + +@item custom_shader_bin +Specifies a complete custom shader as a raw string. +@end table + +@subsubsection Debugging / performance +All of the options in this section default off. They may be of assistance when +attempting to squeeze the maximum performance at the cost of quality. +@table @option +@item skip_aa +Disable anti-aliasing when downscaling. + +@item polar_cutoff +Truncate polar (EWA) scaler kernels below this absolute magnitude, between +@code{0.0} and @code{1.0}. + +@item disable_linear +Disable linear light scaling. + +@item disable_builtin +Disable built-in GPU sampling (forces LUT). + +@item force_icc_lut +Force the use of a full ICC 3DLUT for gamut mapping. + +@item disable_fbos +Forcibly disable FBOs, resulting in loss of almost all functionality, but +offering the maximum possible speed. +@end table + +@subsection Commands +This filter supports almost all of the above options as @ref{commands}. + +@subsection Examples +@itemize +@item +Initialize Vulkan device, upload, filter conversion to yuv420p, and download. +Note that in specific cases you can get around the need to perform format +conversion by specifying the correct @code{format} filter option corresponding +to the input frames. +@example +ffmpeg -i $INPUT -init_hw_device vulkan -vf hwupload,libplacebo=format=yuv420p,hwdownload,format=yuv420p $OUTPUT +@end example + +@item +Run this filter on the CPU, on systems with Mesa installed (and with the most +expensive options disabled): +@example +ffmpeg ... -init_hw_device vulkan:llvmpipe -vf libplacebo=upscaler=none:downscaler=none:peak_detect=false +@end example + +@item +Tone-map input to standard gamut BT.709 output: +@example +libplacebo=colorspace=bt709:color_primaries=bt709:color_trc=bt709:range=tv +@end example + +@item +Rescale input to fit into standard 1080p, with high quality scaling: +@example +libplacebo=w=1920:h=1080:force_original_aspect_ratio=decrease:normalize_sar=true:upscaler=ewa_lanczos:downscaler=ewa_lanczos +@end example + +@item +Convert input to standard sRGB JPEG: +@example +libplacebo=format=yuv420p:colorspace=bt470bg:color_primaries=bt709:color_trc=iec61966-2-1:range=pc +@end example + +@item +Use higher quality debanding settings: +@example +libplacebo=deband=true:deband_iterations=3:deband_radius=8:deband_threshold=6 +@end example +@end itemize + @section libvmaf Calulate the VMAF (Video Multi-Method Assessment Fusion) score for a