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, 242 insertions, 10 deletions

diff --git a/vp8/encoder/picklpf.c b/vp8/encoder/picklpf.c
index beefe8d8e..171ec3a4d 100644
--- a/vp8/encoder/picklpf.c
+++ b/vp8/encoder/picklpf.c
@@ -36,6 +36,15 @@ extern void
 (*vp8_yv12_copy_partial_frame_ptr)(YV12_BUFFER_CONFIG *src_ybc,
                                    YV12_BUFFER_CONFIG *dst_ybc,
                                    int Fraction);
+
+extern void vp8_loop_filter_frame_segment
+(
+    VP8_COMMON *cm,
+    MACROBLOCKD *xd,
+    int default_filt_lvl,
+    int segment
+);
+
 void
 vp8_yv12_copy_partial_frame(YV12_BUFFER_CONFIG *src_ybc, YV12_BUFFER_CONFIG *dst_ybc, int Fraction)
 {
@@ -63,7 +72,6 @@ vp8_yv12_copy_partial_frame(YV12_BUFFER_CONFIG *src_ybc, YV12_BUFFER_CONFIG *dst
 
     vpx_memcpy(dst_y, src_y, ystride *(linestocopy + 16));
 }
-
 static int vp8_calc_partial_ssl_err(YV12_BUFFER_CONFIG *source, YV12_BUFFER_CONFIG *dest, int Fraction, const vp8_variance_rtcd_vtable_t *rtcd)
 {
     int i, j;
@@ -107,18 +115,21 @@ static int vp8_calc_partial_ssl_err(YV12_BUFFER_CONFIG *source, YV12_BUFFER_CONF
 static int get_min_filter_level(VP8_COMP *cpi, int base_qindex)
 {
     int min_filter_level;
+    /*int q = (int) vp8_convert_qindex_to_q(base_qindex);
 
     if (cpi->source_alt_ref_active && cpi->common.refresh_golden_frame && !cpi->common.refresh_alt_ref_frame)
         min_filter_level = 0;
     else
     {
-        if (base_qindex <= 6)
+        if (q <= 10)
             min_filter_level = 0;
-        else if (base_qindex <= 16)
+        else if (q <= 64)
             min_filter_level = 1;
         else
-            min_filter_level = (base_qindex / 8);
+            min_filter_level = (q >> 6);
     }
+    */
+    min_filter_level = 0;
 
     return min_filter_level;
 }
@@ -256,17 +267,232 @@ void vp8cx_pick_filter_level_fast(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
 // Stub function for now Alt LF not used
 void vp8cx_set_alt_lf_level(VP8_COMP *cpi, int filt_val)
 {
-    MACROBLOCKD *mbd = &cpi->mb.e_mbd;
-    (void) filt_val;
+}
+#if CONFIG_FEATUREUPDATES
+void vp8cx_pick_filter_level_sg(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi, int segment)
+{
+    VP8_COMMON *cm = &cpi->common;
+
+    int best_err = 0;
+    int filt_err = 0;
+    int min_filter_level = get_min_filter_level(cpi, cm->base_qindex);
+    int max_filter_level = get_max_filter_level(cpi, cm->base_qindex);
+
+    int filter_step;
+    int filt_high = 0;
+    int filt_mid = cm->filter_level;      // Start search at previous frame filter level
+    int filt_low = 0;
+    int filt_best;
+    int filt_direction = 0;
+
+    int Bias = 0;                       // Bias against raising loop filter and in favour of lowering it
+
+    //  Make a copy of the unfiltered / processed recon buffer
+#if HAVE_ARMV7
+#if CONFIG_RUNTIME_CPU_DETECT
+    if (cm->rtcd.flags & HAS_NEON)
+#endif
+    {
+        vp8_yv12_copy_frame_yonly_no_extend_frame_borders_neon(cm->frame_to_show, &cpi->last_frame_uf);
+    }
+#if CONFIG_RUNTIME_CPU_DETECT
+    else
+#endif
+#endif
+#if !HAVE_ARMV7 || CONFIG_RUNTIME_CPU_DETECT
+    {
+        vp8_yv12_copy_frame_ptr(cm->frame_to_show, &cpi->last_frame_uf);
+    }
+#endif
+
+    if (cm->frame_type == KEY_FRAME)
+        cm->sharpness_level = 0;
+    else
+        cm->sharpness_level = cpi->oxcf.Sharpness;
+
+    // Start the search at the previous frame filter level unless it is now out of range.
+    filt_mid = cm->filter_level;
+
+    if (filt_mid < min_filter_level)
+        filt_mid = min_filter_level;
+    else if (filt_mid > max_filter_level)
+        filt_mid = max_filter_level;
+
+    // Define the initial step size
+    filter_step = (filt_mid < 16) ? 4 : filt_mid / 4;
+
+    // Get baseline error score
+    vp8cx_set_alt_lf_level(cpi, filt_mid);
+    vp8_loop_filter_frame_segment(cm, &cpi->mb.e_mbd, filt_mid,segment);
+
+    best_err = vp8_calc_ss_err(sd, cm->frame_to_show, IF_RTCD(&cpi->rtcd.variance));
+    filt_best = filt_mid;
+
+    //  Re-instate the unfiltered frame
+#if HAVE_ARMV7
+#if CONFIG_RUNTIME_CPU_DETECT
+    if (cm->rtcd.flags & HAS_NEON)
+#endif
+    {
+        vp8_yv12_copy_frame_yonly_no_extend_frame_borders_neon(&cpi->last_frame_uf, cm->frame_to_show);
+    }
+#if CONFIG_RUNTIME_CPU_DETECT
+    else
+#endif
+#endif
+#if !HAVE_ARMV7 || CONFIG_RUNTIME_CPU_DETECT
+    {
+        vp8_yv12_copy_frame_yonly_ptr(&cpi->last_frame_uf, cm->frame_to_show);
+    }
+#endif
+
+    while (filter_step > 0)
+    {
+        Bias = (best_err >> (15 - (filt_mid / 8))) * filter_step; //PGW change 12/12/06 for small images
+
+        // jbb chg: 20100118 - in sections with lots of new material coming in don't bias as much to a low filter value
+        if (cpi->twopass.section_intra_rating < 20)
+            Bias = Bias * cpi->twopass.section_intra_rating / 20;
+
+        // yx, bias less for large block size
+        if(cpi->common.txfm_mode == ALLOW_8X8)
+            Bias >>= 1;
+
+        filt_high = ((filt_mid + filter_step) > max_filter_level) ? max_filter_level : (filt_mid + filter_step);
+        filt_low = ((filt_mid - filter_step) < min_filter_level) ? min_filter_level : (filt_mid - filter_step);
 
-    mbd->segment_feature_data[MB_LVL_ALT_LF][0] = cpi->segment_feature_data[MB_LVL_ALT_LF][0];
-    mbd->segment_feature_data[MB_LVL_ALT_LF][1] = cpi->segment_feature_data[MB_LVL_ALT_LF][1];
-    mbd->segment_feature_data[MB_LVL_ALT_LF][2] = cpi->segment_feature_data[MB_LVL_ALT_LF][2];
-    mbd->segment_feature_data[MB_LVL_ALT_LF][3] = cpi->segment_feature_data[MB_LVL_ALT_LF][3];
+        if ((filt_direction <= 0) && (filt_low != filt_mid))
+        {
+            // Get Low filter error score
+            vp8cx_set_alt_lf_level(cpi, filt_low);
+            vp8_loop_filter_frame_segment(cm, &cpi->mb.e_mbd, filt_low, segment);
+
+            filt_err = vp8_calc_ss_err(sd, cm->frame_to_show, IF_RTCD(&cpi->rtcd.variance));
+
+            //  Re-instate the unfiltered frame
+#if HAVE_ARMV7
+#if CONFIG_RUNTIME_CPU_DETECT
+            if (cm->rtcd.flags & HAS_NEON)
+#endif
+            {
+                vp8_yv12_copy_frame_yonly_no_extend_frame_borders_neon(&cpi->last_frame_uf, cm->frame_to_show);
+            }
+#if CONFIG_RUNTIME_CPU_DETECT
+            else
+#endif
+#endif
+#if !HAVE_ARMV7 || CONFIG_RUNTIME_CPU_DETECT
+            {
+                vp8_yv12_copy_frame_yonly_ptr(&cpi->last_frame_uf, cm->frame_to_show);
+            }
+#endif
+
+            // If value is close to the best so far then bias towards a lower loop filter value.
+            if ((filt_err - Bias) < best_err)
+            {
+                // Was it actually better than the previous best?
+                if (filt_err < best_err)
+                    best_err = filt_err;
+
+                filt_best = filt_low;
+            }
+        }
+
+        // Now look at filt_high
+        if ((filt_direction >= 0) && (filt_high != filt_mid))
+        {
+            vp8cx_set_alt_lf_level(cpi, filt_high);
+            vp8_loop_filter_frame_segment(cm, &cpi->mb.e_mbd, filt_high, segment);
+
+            filt_err = vp8_calc_ss_err(sd, cm->frame_to_show, IF_RTCD(&cpi->rtcd.variance));
+
+            //  Re-instate the unfiltered frame
+#if HAVE_ARMV7
+#if CONFIG_RUNTIME_CPU_DETECT
+            if (cm->rtcd.flags & HAS_NEON)
+#endif
+            {
+                vp8_yv12_copy_frame_yonly_no_extend_frame_borders_neon(&cpi->last_frame_uf, cm->frame_to_show);
+            }
+#if CONFIG_RUNTIME_CPU_DETECT
+            else
+#endif
+#endif
+#if !HAVE_ARMV7 || CONFIG_RUNTIME_CPU_DETECT
+            {
+                vp8_yv12_copy_frame_yonly_ptr(&cpi->last_frame_uf, cm->frame_to_show);
+            }
+#endif
+
+            // Was it better than the previous best?
+            if (filt_err < (best_err - Bias))
+            {
+                best_err = filt_err;
+                filt_best = filt_high;
+            }
+        }
+
+        // Half the step distance if the best filter value was the same as last time
+        if (filt_best == filt_mid)
+        {
+            filter_step = filter_step / 2;
+            filt_direction = 0;
+        }
+        else
+        {
+            filt_direction = (filt_best < filt_mid) ? -1 : 1;
+            filt_mid = filt_best;
+        }
+    }
+
+    cm->filter_level = filt_best;
 }
 
 void vp8cx_pick_filter_level(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
 {
+    VP8_COMMON *oci = &cpi->common;
+    MODE_INFO *mi = oci->mi;
+    int filt_lev[2];
+    int i, j;
+    MACROBLOCKD * const xd = &cpi->mb.e_mbd;
+    int max_seg;
+    int mb_index = 0;
+
+    // pick the loop filter for each segment after segment 0
+    for (i = 1; i < MAX_MB_SEGMENTS; i++)
+    {
+        // if the segment loop filter is active
+        if (segfeature_active(xd, i, SEG_LVL_ALT_LF))
+        {
+            set_segdata(xd, i, SEG_LVL_ALT_LF, 0);
+            vp8cx_pick_filter_level_sg(sd, cpi, i);
+            filt_lev[i] = oci->filter_level;
+        }
+    }
+
+    // do the 0 segment ( this filter also picks the filter value for all
+    // the not enabled features )
+
+    // TODO : Fix the code if segment 0 is the one with seg_lvl_alt_lf on
+    // right now assumes segment 0 gets base loop filter and the rest are
+    // deltas off of segment 0.
+    set_segdata(xd, 0, SEG_LVL_ALT_LF, 0);
+    vp8cx_pick_filter_level_sg(sd, cpi, 0);
+    filt_lev[0] = oci->filter_level;
+
+    // convert the best filter level for the mbs of the segment to
+    // a delta from 0
+    for (i = 1; i < MAX_MB_SEGMENTS; i++)
+        if (segfeature_active(xd, i, SEG_LVL_ALT_LF))
+        {
+            set_segdata(xd, i, SEG_LVL_ALT_LF, filt_lev[i] - filt_lev[0]);
+            xd->update_mb_segmentation_data !=
+                                    segfeature_changed( xd,i,SEG_LVL_ALT_LF);
+        }
+}
+#else
+void vp8cx_pick_filter_level(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
+{
     VP8_COMMON *cm = &cpi->common;
 
     int best_err = 0;
@@ -350,6 +576,10 @@ void vp8cx_pick_filter_level(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
         if (cpi->twopass.section_intra_rating < 20)
             Bias = Bias * cpi->twopass.section_intra_rating / 20;
 
+        // yx, bias less for large block size
+        if(cpi->common.txfm_mode == ALLOW_8X8)
+            Bias >>= 1;
+
         filt_high = ((filt_mid + filter_step) > max_filter_level) ? max_filter_level : (filt_mid + filter_step);
         filt_low = ((filt_mid - filter_step) < min_filter_level) ? min_filter_level : (filt_mid - filter_step);
 
@@ -439,3 +669,5 @@ void vp8cx_pick_filter_level(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
 
     cm->filter_level = filt_best;
 }
+#endif
+