Variance Partition

Functions
void	av1_set_variance_partition_thresholds (AV1_COMP *cpi, int q, int content_lowsumdiff)
	Set the thresholds for variance based partition.
int	av1_choose_var_based_partitioning (AV1_COMP *cpi, const TileInfo *const tile, ThreadData *td, MACROBLOCK *x, int mi_row, int mi_col)
	Variance based partition selection.

Detailed Description

This module describes variance partition algorithm in AV1. More details will be added.

Function Documentation

av1_set_variance_partition_thresholds()

void av1_set_variance_partition_thresholds	(	AV1_COMP *	cpi,
		int	q,
		int	content_lowsumdiff )

Set the thresholds for variance based partition.

Set the variance split thresholds for following the block sizes: 0 - threshold_128x128, 1 - threshold_64x64, 2 - threshold_32x32, 3 - vbp_threshold_16x16. 4 - vbp_threshold_8x8 (to split to 4x4 partition) is currently only used on key frame. The thresholds are based om Q, resolution, noise level, and content state.

Parameters

[in]	cpi	Top level encoder structure
[in]	q	q index
[in]	content_lowsumdiff	Low sumdiff flag for superblock

Remarks

Returns the set of thresholds in cpi->vbp_info.thresholds.

Referenced by encode_with_recode_loop(), and encode_without_recode().

av1_choose_var_based_partitioning()

int av1_choose_var_based_partitioning	(	AV1_COMP *	cpi,
		const TileInfo *const	tile,
		ThreadData *	td,
		MACROBLOCK *	x,
		int	mi_row,
		int	mi_col )

Variance based partition selection.

Select the partitioning based on the variance of the residual signal, residual generated as the difference between the source and prediction. The prediction is the reconstructed LAST or reconstructed GOLDEN, whichever has lower y sad. For LAST, option exists (speed feature) to use motion compensation based on superblock motion via int_pro_motion_estimation. For key frames reference is fixed 128 level, so variance is the source variance. The variance is computed for downsampled inputs (8x8 or 4x4 downsampled), and selection is done top-down via as set of partition thresholds. defined for each block level, and set based on Q, resolution, noise level, and content state.

Parameters

[in]	cpi	Top level encoder structure
[in]	tile	Pointer to TileInfo
[in]	td	Pointer to ThreadData
[in]	x	Pointer to MACROBLOCK
[in]	mi_row	Row coordinate of the superblock in a step size of MI_SIZE
[in]	mi_col	Column coordinate of the super block in a step size of MI_SIZE

Returns

Returns the partition in xd->mi[0]->sb_type. Also sets the low temporal variance flag and the color sensitivity flag (both used in nonrd_pickmode).

Referenced by encode_nonrd_sb(), and encode_rd_sb().