WebM Experimental Codec Branch Snapshot

This is a code snapshot of experimental work currently ongoing for a
next-generation codec.

The codebase has been cut down considerably from the libvpx baseline.
For example, we are currently only supporting VBR 2-pass rate control
and have removed most of the code relating to coding speed, threading,
error resilience, partitions and various other features.  This is in
part to make the codebase easier to work on and experiment with, but
also because we want to have an open discussion about how the bitstream
will be structured and partitioned and not have that conversation
constrained by past work.

Our basic working pattern has been to initially encapsulate experiments
using configure options linked to #IF CONFIG_XXX statements in the
code. Once experiments have matured and we are reasonably happy that
they give benefit and can be merged without breaking other experiments,
we remove the conditional compile statements and merge them in.

Current changes include:
* Temporal coding experiment for segments (though still only 4 max, it
  will likely be increased).
* Segment feature experiment - to allow various bits of information to
  be coded at the segment level. Features tested so far include mode
  and reference frame information, limiting end of block offset and
  transform size, alongside Q and loop filter parameters, but this set
  is very fluid.
* Support for 8x8 transform - 8x8 dct with 2nd order 2x2 haar is used
  in MBs using 16x16 prediction modes within inter frames.
* Compound prediction (combination of signals from existing predictors
  to create a new predictor).
* 8 tap interpolation filters and 1/8th pel motion vectors.
* Loop filter modifications.
* Various entropy modifications and changes to how entropy contexts and
  updates are handled.
* Extended quantizer range matched to transform precision improvements.

There are also ongoing further experiments that we hope to merge in the
near future: For example, coding of motion and other aspects of the
prediction signal to better support larger image formats, use of larger
block sizes (e.g. 32x32 and up) and lossless non-transform based coding
options (especially for key frames). It is our hope that we will be
able to make regular updates and we will warmly welcome community
contributions.

Please be warned that, at this stage, the codebase is currently slower
than VP8 stable branch as most new code has not been optimized, and
even the 'C' has been deliberately written to be simple and obvious,
not fast.

The following graphs have the initial test results, numbers in the
tables measure the compression improvement in terms of percentage. The
build has  the following optional experiments configured:
--enable-experimental --enable-enhanced_interp --enable-uvintra
--enable-high_precision_mv --enable-sixteenth_subpel_uv

CIF Size clips:
http://getwebm.org/tmp/cif/
HD size clips:
http://getwebm.org/tmp/hd/
(stable_20120309 represents encoding results of WebM master branch
build as of commit#7a15907)

They were encoded using the following encode parameters:
--good --cpu-used=0 -t 0 --lag-in-frames=25 --min-q=0 --max-q=63
--end-usage=0 --auto-alt-ref=1 -p 2 --pass=2 --kf-max-dist=9999
--kf-min-dist=0 --drop-frame=0 --static-thresh=0 --bias-pct=50
--minsection-pct=0 --maxsection-pct=800 --sharpness=0
--arnr-maxframes=7 --arnr-strength=3(for HD,6 for CIF)
--arnr-type=3

Change-Id: I5c62ed09cfff5815a2bb34e7820d6a810c23183c

1 files changed, 92 insertions, 22 deletions

diff --git a/vp8/common/blockd.h b/vp8/common/blockd.h
index 6cb3fe1bb..89fe03516 100644
--- a/vp8/common/blockd.h
+++ b/vp8/common/blockd.h
@@ -14,21 +14,26 @@
 
 void vpx_log(const char *format, ...);
 
-#include "vpx_config.h"
+#include "vpx_ports/config.h"
 #include "vpx_scale/yv12config.h"
 #include "mv.h"
 #include "treecoder.h"
 #include "subpixel.h"
 #include "vpx_ports/mem.h"
+#include "common.h"
 
 #define TRUE    1
 #define FALSE   0
 
+//#define MODE_STATS
+
 /*#define DCPRED 1*/
 #define DCPREDSIMTHRESH 0
 #define DCPREDCNTTHRESH 3
 
 #define MB_FEATURE_TREE_PROBS   3
+#define PREDICTION_PROBS 3
+
 #define MAX_MB_SEGMENTS         4
 
 #define MAX_REF_LF_DELTAS       4
@@ -60,11 +65,13 @@ typedef struct
 
 extern const unsigned char vp8_block2left[25];
 extern const unsigned char vp8_block2above[25];
+extern const unsigned char vp8_block2left_8x8[25];
+extern const unsigned char vp8_block2above_8x8[25];
+
 
 #define VP8_COMBINEENTROPYCONTEXTS( Dest, A, B) \
     Dest = ((A)!=0) + ((B)!=0);
 
-
 typedef enum
 {
     KEY_FRAME = 0,
@@ -77,6 +84,7 @@ typedef enum
     V_PRED,             /* vertical prediction */
     H_PRED,             /* horizontal prediction */
     TM_PRED,            /* Truemotion prediction */
+    I8X8_PRED,           /* 8x8 based prediction, each 8x8 has its own prediction mode */
     B_PRED,             /* block based prediction, each block has its own prediction mode */
 
     NEARESTMV,
@@ -88,21 +96,32 @@ typedef enum
     MB_MODE_COUNT
 } MB_PREDICTION_MODE;
 
-/* Macroblock level features */
+// Segment level features.
 typedef enum
 {
-    MB_LVL_ALT_Q = 0,               /* Use alternate Quantizer .... */
-    MB_LVL_ALT_LF = 1,              /* Use alternate loop filter value... */
-    MB_LVL_MAX = 2                  /* Number of MB level features supported */
+    SEG_LVL_ALT_Q = 0,               // Use alternate Quantizer ....
+    SEG_LVL_ALT_LF = 1,              // Use alternate loop filter value...
+    SEG_LVL_REF_FRAME = 2,           // Optional Segment reference frame
+    SEG_LVL_MODE = 3,                // Optional Segment mode
+    SEG_LVL_EOB = 4,                 // EOB end stop marker.
+    SEG_LVL_TRANSFORM = 5,           // Block transform size.
+    SEG_LVL_MAX = 6                  // Number of MB level features supported
 
-} MB_LVL_FEATURES;
+} SEG_LVL_FEATURES;
 
-/* Segment Feature Masks */
-#define SEGMENT_ALTQ    0x01
-#define SEGMENT_ALT_LF  0x02
+// Segment level features.
+typedef enum
+{
+    TX_4X4 = 0,                      // 4x4 dct transform
+    TX_8X8 = 1,                      // 8x8 dct transform
+
+    TX_SIZE_MAX = 2                  // Number of differnt transforms avaialble
+
+} TX_SIZE;
 
 #define VP8_YMODES  (B_PRED + 1)
 #define VP8_UV_MODES (TM_PRED + 1)
+#define VP8_I8X8_MODES (TM_PRED + 1)
 
 #define VP8_MVREFS (1 + SPLITMV - NEARESTMV)
 
@@ -139,7 +158,12 @@ typedef enum
 
 union b_mode_info
 {
-    B_PREDICTION_MODE as_mode;
+    struct {
+        B_PREDICTION_MODE first;
+#if CONFIG_COMP_INTRA_PRED
+        B_PREDICTION_MODE second;
+#endif
+    } as_mode;
     int_mv mv;
 };
 
@@ -155,13 +179,26 @@ typedef enum
 typedef struct
 {
     MB_PREDICTION_MODE mode, uv_mode;
-    MV_REFERENCE_FRAME ref_frame;
-    int_mv mv;
-
+#if CONFIG_COMP_INTRA_PRED
+    MB_PREDICTION_MODE second_mode, second_uv_mode;
+#endif
+    MV_REFERENCE_FRAME ref_frame, second_ref_frame;
+    TX_SIZE txfm_size;
+    int_mv mv, second_mv;
     unsigned char partitioning;
     unsigned char mb_skip_coeff;                                /* does this mb has coefficients at all, 1=no coefficients, 0=need decode tokens */
     unsigned char need_to_clamp_mvs;
     unsigned char segment_id;                  /* Which set of segmentation parameters should be used for this MB */
+
+    // Flags used for prediction status of various bistream signals
+    unsigned char seg_id_predicted;
+    unsigned char ref_predicted;
+
+    // Indicates if the mb is part of the image (1) vs border (0)
+    // This can be useful in determining whether the MB provides
+    // a valid predictor
+    unsigned char mb_in_image;
+
 } MB_MODE_INFO;
 
 typedef struct
@@ -205,8 +242,12 @@ typedef struct MacroBlockD
     int fullpixel_mask;
 
     YV12_BUFFER_CONFIG pre; /* Filtered copy of previous frame reconstruction */
+    struct {
+        uint8_t *y_buffer, *u_buffer, *v_buffer;
+    } second_pre;
     YV12_BUFFER_CONFIG dst;
 
+    MODE_INFO *prev_mode_info_context;
     MODE_INFO *mode_info_context;
     int mode_info_stride;
 
@@ -229,13 +270,24 @@ typedef struct MacroBlockD
     unsigned char update_mb_segmentation_data;
 
     /* 0 (do not update) 1 (update) the macroblock segmentation feature data. */
-    unsigned char mb_segement_abs_delta;
+    unsigned char mb_segment_abs_delta;
 
     /* Per frame flags that define which MB level features (such as quantizer or loop filter level) */
     /* are enabled and when enabled the proabilities used to decode the per MB flags in MB_MODE_INFO */
-    vp8_prob mb_segment_tree_probs[MB_FEATURE_TREE_PROBS];         /* Probability Tree used to code Segment number */
 
-    signed char segment_feature_data[MB_LVL_MAX][MAX_MB_SEGMENTS];            /* Segment parameters */
+    // Probability Tree used to code Segment number
+    vp8_prob mb_segment_tree_probs[MB_FEATURE_TREE_PROBS];
+
+
+    // Segment features
+    signed char segment_feature_data[MAX_MB_SEGMENTS][SEG_LVL_MAX];
+    unsigned int segment_feature_mask[MAX_MB_SEGMENTS];
+
+#if CONFIG_FEATUREUPDATES
+    // keep around the last set so we can figure out what updates...
+    unsigned int old_segment_feature_mask[MAX_MB_SEGMENTS];
+    signed char old_segment_feature_data[MAX_MB_SEGMENTS][SEG_LVL_MAX];
+#endif
 
     /* mode_based Loop filter adjustment */
     unsigned char mode_ref_lf_delta_enabled;
@@ -244,8 +296,8 @@ typedef struct MacroBlockD
     /* Delta values have the range +/- MAX_LOOP_FILTER */
     signed char last_ref_lf_deltas[MAX_REF_LF_DELTAS];                /* 0 = Intra, Last, GF, ARF */
     signed char ref_lf_deltas[MAX_REF_LF_DELTAS];                     /* 0 = Intra, Last, GF, ARF */
-    signed char last_mode_lf_deltas[MAX_MODE_LF_DELTAS];                      /* 0 = BPRED, ZERO_MV, MV, SPLIT */
-    signed char mode_lf_deltas[MAX_MODE_LF_DELTAS];                           /* 0 = BPRED, ZERO_MV, MV, SPLIT */
+    signed char last_mode_lf_deltas[MAX_MODE_LF_DELTAS];              /* 0 = BPRED, ZERO_MV, MV, SPLIT */
+    signed char mode_lf_deltas[MAX_MODE_LF_DELTAS];                   /* 0 = BPRED, ZERO_MV, MV, SPLIT */
 
     /* Distance of MB away from frame edges */
     int mb_to_left_edge;
@@ -253,15 +305,17 @@ typedef struct MacroBlockD
     int mb_to_top_edge;
     int mb_to_bottom_edge;
 
-    int ref_frame_cost[MAX_REF_FRAMES];
-
-
     unsigned int frames_since_golden;
     unsigned int frames_till_alt_ref_frame;
     vp8_subpix_fn_t  subpixel_predict;
     vp8_subpix_fn_t  subpixel_predict8x4;
     vp8_subpix_fn_t  subpixel_predict8x8;
     vp8_subpix_fn_t  subpixel_predict16x16;
+    vp8_subpix_fn_t  subpixel_predict_avg8x8;
+    vp8_subpix_fn_t  subpixel_predict_avg16x16;
+#if CONFIG_HIGH_PRECISION_MV
+    int allow_high_precision_mv;
+#endif /* CONFIG_HIGH_PRECISION_MV */
 
     void *current_bc;
 
@@ -284,4 +338,20 @@ typedef struct MacroBlockD
 extern void vp8_build_block_doffsets(MACROBLOCKD *x);
 extern void vp8_setup_block_dptrs(MACROBLOCKD *x);
 
+static void update_blockd_bmi(MACROBLOCKD *xd)
+{
+    int i;
+    int is_4x4;
+    is_4x4 = (xd->mode_info_context->mbmi.mode == SPLITMV) ||
+             (xd->mode_info_context->mbmi.mode == I8X8_PRED) ||
+             (xd->mode_info_context->mbmi.mode == B_PRED);
+
+    if (is_4x4)
+    {
+        for (i = 0; i < 16; i++)
+        {
+            xd->block[i].bmi = xd->mode_info_context->bmi[i];
+        }
+    }
+}
 #endif  /* __INC_BLOCKD_H */