Commit 6439aa5a authored by Jim Bankoski's avatar Jim Bankoski

explain speed features

Added comments to explain what the various speed features do, and removed
1 that was clearly unused.

Change-Id: Icd37a536072ddafedbfaefcecbe48979f6d10faf
parent 21a0c1f3
......@@ -699,7 +699,6 @@ void vp9_set_speed_features(VP9_COMP *cpi) {
// best quality defaults
sf->RD = 1;
sf->search_method = NSTEP;
sf->auto_filter = 1;
sf->recode_loop = 1;
sf->subpel_search_method = SUBPEL_TREE;
sf->subpel_iters_per_step = 2;
......@@ -232,57 +232,185 @@ typedef enum {
typedef struct {
// This flag refers to whether or not to perform rd optimization.
int RD;
// Motion search method (Diamond, NSTEP, Hex, Big Diamond, Square, etc).
SEARCH_METHODS search_method;
int auto_filter;
// Recode_loop can be:
// 0 means we only encode a frame once
// 1 means we can re-encode based on bitrate constraints on any frame
// 2 means we can only recode gold, alt, and key frames.
int recode_loop;
// Subpel_search_method can only be subpel_tree which does a subpixel
// logarithmic search that keeps stepping at 1/2 pixel units until
// you stop getting a gain, and then goes on to 1/4 and repeats
// the same process. Along the way it skips many diagonals.
SUBPEL_SEARCH_METHODS subpel_search_method;
// Maximum number of steps in logarithmic subpel search before giving up.
int subpel_iters_per_step;
// Thresh_mult is used to set a threshold for the rd score. A higher value
// means that we will accept the best mode so far more often. This number
// is used in combination with the current block size, and thresh_freq_fact
// to pick a threshold.
int thresh_mult[MAX_MODES];
int thresh_mult_sub8x8[MAX_REFS];
// This parameter controls the number of steps we'll do in a diamond
// search.
int max_step_search_steps;
// This parameter controls which step in the n-step process we start at.
// It's changed adaptively based on circumstances.
int reduce_first_step_size;
// If this is set to 1, we limit the motion search range to 2 times the
// largest motion vector found in the last frame.
int auto_mv_step_size;
// Trellis (dynamic programming) optimization of quantized values (+1, 0).
int optimize_coefficients;
// Always set to 0. If on it enables 0 cost background transmission
// (except for the initial transmission of the segmentation). The feature is
// disabled because the addition of very large block sizes make the
// backgrounds very to cheap to encode, and the segmentation we have
// adds overhead.
int static_segmentation;
// If 1 we iterate finding a best reference for 2 ref frames together - via
// a log search that iterates 4 times (check around mv for last for best
// error of combined predictor then check around mv for alt). If 0 we
// we just use the best motion vector found for each frame by itself.
int comp_inter_joint_search_thresh;
// This variable is used to cap the maximum number of times we skip testing a
// mode to be evaluated. A high value means we will be faster.
int adaptive_rd_thresh;
// Enables skipping the reconstruction step (idct, recon) in the
// intermediate steps assuming the last frame didn't have too many intra
// blocks and the q is less than a threshold.
int skip_encode_sb;
int skip_encode_frame;
// This variable allows us to reuse the last frames partition choices
// (64x64 v 32x32 etc) for this frame. It can be set to only use the last
// frame as a starting point in low motion scenes or always use it. If set
// we use last partitioning_redo frequency to determine how often to redo
// the partitioning from scratch. Adjust_partitioning_from_last_frame
// enables us to adjust up or down one partitioning from the last frames
// partitioning.
LAST_FRAME_PARTITION_METHOD use_lastframe_partitioning;
// Determine which method we use to determine transform size. We can choose
// between options like full rd, largest for prediction size, largest
// for intra and model coefs for the rest.
TX_SIZE_SEARCH_METHOD tx_size_search_method;
// Low precision 32x32 fdct keeps everything in 16 bits and thus is less
// precise but significantly faster than the non lp version.
int use_lp32x32fdct;
// TODO(JBB): remove this as its no longer used.
// If set partition size will always be always_this_block_size.
int use_one_partition_size_always;
// Skip rectangular partition test when partition type none gives better
// rd than partition type split.
int less_rectangular_check;
// Disable testing non square partitions. (eg 16x32)
int use_square_partition_only;
// After looking at the first set of modes (set by index here), skip
// checking modes for reference frames that don't match the reference frame
// of the best so far.
int mode_skip_start;
// TODO(JBB): Remove this.
int reference_masking;
// Used in conjunction with use_one_partition_size_always.
BLOCK_SIZE always_this_block_size;
// Sets min and max partition sizes for this 64x64 region based on the
// same superblock in last encoded frame, and the left and above neighbor
// in this block.
int auto_min_max_partition_size;
// Min and max partition size we enable (block_size) as per auto
// min max, but also used by adjust partitioning, and pick_partitioning.
BLOCK_SIZE min_partition_size;
BLOCK_SIZE max_partition_size;
// Whether or not we allow partitions one smaller or one greater than the last
// frame's partitioning. Only used if use_lastframe_partitioning is set.
int adjust_partitioning_from_last_frame;
// How frequently we re do the partitioning from scratch. Only used if
// use_lastframe_partitioning is set.
int last_partitioning_redo_frequency;
// Disables sub 8x8 blocksizes in different scenarios: Choices are to disable
// it always, to allow it for only Last frame and Intra, disable it for all
// inter modes or to enable it always.
int disable_split_mask;
// TODO(jbb): Remove this and everything that uses it. It's only valid if
// we were doing small to large partition checks. We currently do the
// reverse.
int using_small_partition_info;
// TODO(jingning): combine the related motion search speed features
// This allows us to use motion search at other sizes as a starting
// point for this motion search and limits the search range around it.
int adaptive_motion_search;
// Allows sub 8x8 modes to use the prediction filter that was determined
// best for 8x8 mode. If set to 0 we always re check all the filters for
// sizes less than 8x8, 1 means we check all filter modes if no 8x8 filter
// was selected, and 2 means we use 8 tap if no 8x8 filter mode was selected.
int adaptive_pred_filter_type;
// Implements various heuristics to skip searching modes
// The heuristics selected are based on flags
// defined in the MODE_SEARCH_SKIP_HEURISTICS enum
unsigned int mode_search_skip_flags;
// A source variance threshold below which the split mode is disabled
unsigned int disable_split_var_thresh;
// A source variance threshold below which filter search is disabled
// Choose a very large value (UINT_MAX) to use 8-tap always
unsigned int disable_filter_search_var_thresh;
// These bit masks allow you to enable or disable intra modes for each
// transform size separately.
int intra_y_mode_mask[TX_SIZES];
int intra_uv_mode_mask[TX_SIZES];
// This variable enables an early break out of mode testing if the model for
// rd built from the prediction signal indicates a value that's much
// higher than the best rd we've seen so far.
int use_rd_breakout;
// This enables us to use an estimate for intra rd based on dc mode rather
// than choosing an actual uv mode in the stage of encoding before the actual
// final encode.
int use_uv_intra_rd_estimate;
// This picks a loop filter strength by trying a small portion of the image
// with different values.
int use_fast_lpf_pick;
// This feature limits the number of coefficients updates we actually do
// by only looking at counts from 1/2 the bands.
int use_fast_coef_updates; // 0: 2-loop, 1: 1-loop, 2: 1-loop reduced
......@@ -601,7 +729,7 @@ typedef struct VP9_COMP {
int *mb_norm_activity_map;
int output_partition;
/* force next frame to intra when kf_auto says so */
// Force next frame to intra when kf_auto says so.
int force_next_frame_intra;
int droppable;
......@@ -643,7 +771,7 @@ typedef struct VP9_COMP {
int64_t mode_test_hits[BLOCK_SIZES];
/* Y,U,V,(A) */
// Y,U,V,(A)
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