ffmpeg-scaler1

Overview

The FFmpeg rescaler provides a high-level interface to the libswscale library image conversion utilities. In particular it allows one to perform image rescaling and pixel format conversion.

Options

The video scaler supports the following named options.

Options may be set by specifying -option value in the FFmpeg tools, with a few API-only exceptions noted below. For programmatic use, they can be set explicitly in the "SwsContext" options or through the libavutil/opt.h API.

scaler, scaler_sub

Choose the scaling algorithm to use. Default value is auto for both. It accepts the following values:

auto

Aumotic choice. For scaler_sub, this means the same algorithm as scaler. For scaler, this defaults to the scaler flag selected by sws_flags.

bilinear

Bilinear filter. (AKA triangle filter)

bicubic

2-tap cubic BC-spline (AKA Mitchell-Netravali spline). The B and C parameters can be configured by setting "param0" and "param1", defaulting to 0.0 and 0.6 respectively.

point, neighbor

Point sampling (AKA nearest neighbor).

area

Area averaging. Equivalent to bilinear for upscaling.

gaussian

2-tap Gaussian filter approximation. The sharpness parameter can be configured by setting "param0", defaulting to 3.0.

sinc

Unwindowed sinc filter.

lanczos

Lanczos resampling (sinc windowed sinc). The number of filter taps can be configured by setting "param0", defaulting to 3.

spline

Unwindowed natural bicubic spline.

sws_flags

Set the scaler flags. This is also used to set the scaling algorithm, though this usage is deprecated in favor of setting scaler. Only a single algorithm may be selected. Default value is bicubic.

It accepts the following values:

fast_bilinear

Select fast bilinear scaling algorithm. (Deprecated)

bilinear

Select bilinear scaling algorithm. (Deprecated)

bicubic

Select bicubic scaling algorithm. (Deprecated)

experimental

Select experimental scaling algorithm. (Deprecated)

neighbor

Select nearest neighbor rescaling algorithm. (Deprecated)

area

Select averaging area rescaling algorithm. (Deprecated)

bicublin

Select bicubic scaling algorithm for the luma component, bilinear for chroma components. (Deprecated)

gauss

Select Gaussian rescaling algorithm. (Deprecated)

sinc

Select sinc rescaling algorithm. (Deprecated)

lanczos

Select Lanczos rescaling algorithm. The default width (alpha) is 3 and can be changed by setting "param0". (Deprecated)

spline

Select natural bicubic spline rescaling algorithm. (Deprecated)

print_info

Enable printing/debug logging.

accurate_rnd

Enable accurate rounding.

full_chroma_int

Enable full chroma interpolation.

full_chroma_inp

Select full chroma input.

bitexact

Enable bitexact output.

unstable

Allow the use of experimental new code. May subtly affect the output or even produce wrong results. For testing only.

srcw (API only)

Set source width.

srch (API only)

Set source height.

dstw (API only)

Set destination width.

dsth (API only)

Set destination height.

src_format (API only)

Set source pixel format (must be expressed as an integer).

dst_format (API only)

Set destination pixel format (must be expressed as an integer).

src_range (boolean)

If value is set to 1, indicates source is full range. Default value is 0, which indicates source is limited range.

dst_range (boolean)

If value is set to 1, enable full range for destination. Default value is 0, which enables limited range.

gamma (boolean)

If value is set to 1, enable gamma correct scaling. Default value is 0.

param0, param1

Set scaling algorithm parameters. The specified values are specific of some scaling algorithms and ignored by others. The specified values are floating point number values.

sws_dither

Set the dithering algorithm. Accepts one of the following values. Default value is auto.

auto

automatic choice

none

no dithering

bayer

bayer dither

ed

error diffusion dither

a_dither

arithmetic dither, based using addition

x_dither

arithmetic dither, based using xor (more random/less apparent patterning that a_dither).

alphablend

Set the alpha blending to use when the input has alpha but the output does not. Default value is none.

uniform_color

Blend onto a uniform background color

checkerboard

Blend onto a checkerboard

none

No blending

sws_backends

Set the allowed swscale backends. This is a flags option, so multiple backends may be combined.

auto

Automatic selection. Equal to either stable or all depending on whether or not the unstable flag is set. This is the default value.

stable

All stable backends.

unstable

All unstable backends.

all

All available backends.

legacy

Legacy swscale code.

c

Template-based reference code.

memcpy

Fast path using libc "memcpy".

x86

x86 SIMD kernels.

aarch64

AArch64 NEON kernels.

spirv

Vulkan SPIR-V backend.