filters.h File Reference

#include <libavutil/refstruct.h>

Go to the source code of this file.

Data Structures
struct	SwsFilterParams
struct	SwsFilterWeights
	Represents a computed filter kernel. More...

Macros
#define	SWS_NUM_SCALER_PARAMS   2
#define	SWS_MAX_REDUCE_CUTOFF   0.002
#define	SWS_PARAM_DEFAULT   123456

Enumerations
enum	SwsScaler {   SWS_SCALE_AUTO = 0, SWS_SCALE_BILINEAR, SWS_SCALE_BICUBIC, SWS_SCALE_POINT,   SWS_SCALE_AREA, SWS_SCALE_GAUSSIAN, SWS_SCALE_SINC, SWS_SCALE_LANCZOS,   SWS_SCALE_SPLINE, SWS_SCALE_NB, SWS_SCALE_MAX_ENUM = 0x7FFFFFFF }
enum	{ SWS_FILTER_SCALE = (1 << 14), SWS_FILTER_SIZE_MAX = 256 }

Functions
int	ff_sws_filter_generate (void *log_ctx, const SwsFilterParams *params, SwsFilterWeights **out)
	Generate a filter kernel for the given parameters. More...

Macro Definition Documentation

SWS_NUM_SCALER_PARAMS

#define SWS_NUM_SCALER_PARAMS   2

Definition at line 40 of file filters.h.

SWS_MAX_REDUCE_CUTOFF

#define SWS_MAX_REDUCE_CUTOFF   0.002

Definition at line 41 of file filters.h.

SWS_PARAM_DEFAULT

#define SWS_PARAM_DEFAULT   123456

Definition at line 42 of file filters.h.

Enumeration Type Documentation

SwsScaler

enum SwsScaler

Enumerator
SWS_SCALE_AUTO
SWS_SCALE_BILINEAR	bilinear filtering
SWS_SCALE_BICUBIC	2-tap cubic BC-spline
SWS_SCALE_POINT	nearest neighbor (point sampling)
SWS_SCALE_AREA	area averaging
SWS_SCALE_GAUSSIAN	2-tap gaussian approximation
SWS_SCALE_SINC	unwindowed sinc
SWS_SCALE_LANCZOS	3-tap sinc/sinc
SWS_SCALE_SPLINE	unwindowned natural cubic spline
SWS_SCALE_NB	not part of the ABI
SWS_SCALE_MAX_ENUM	force size to 32 bits, not a valid filter type

Definition at line 26 of file filters.h.

anonymous enum

anonymous enum

Enumerator
SWS_FILTER_SCALE	14-bit coefficients are picked to fit comfortably within int16_t for efficient SIMD processing (e.g. pmaddwd on x86). Conversely, this limits the maximum filter size to 256, to avoid excessive precision loss. (Consider that 14 - 8 = 6 bit effective weight resolution) Note that this limitation would not apply to floating-point filters, and in a future update to this code, we could gain the ability to generate unbounded floating point filters directly.
SWS_FILTER_SIZE_MAX

Definition at line 45 of file filters.h.

Function Documentation

ff_sws_filter_generate()

int ff_sws_filter_generate	(	void *	log_ctx,
		const SwsFilterParams *	params,
		SwsFilterWeights **	out
	)

Generate a filter kernel for the given parameters.

The generated filter is allocated as a refstruct and must be unref'd by the caller.

Returns 0 or a negative error code. In particular, this may return:

• AVERROR(ENOMEM) if memory allocation fails.
• AVERROR(EINVAL) if the provided parameters are invalid (e.g. out of range).
• AVERROR(ENOTSUP) if the generated filter would exceed SWS_FILTER_SIZE_MAX.

SWS_SCALE_AREA is a pseudo-filter that is equivalent to bilinear filtering for upscaling (since bilinear just evenly mixes samples according to the relative distance), and equivalent to (anti-aliased) point sampling for downscaling.

Definition at line 185 of file filters.c.

Referenced by cudascale_filter_init().