filters.h File Reference

#include <libavutil/refstruct.h>
#include "swscale.h"

Go to the source code of this file.

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

Enumerations
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...

Enumeration Type Documentation

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 29 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 183 of file filters.c.

Referenced by check_filter().