video-converter: add table based matrix8 implementation

Based on patch from Mozzhuhin Andrey <nopscmn at gmail.com>

Add a table based matrix8 multiplication implementation. The algorithm
does not do any clipping so we need to make sure we never call this on
input that might need to be clipped. In general, this algorithm is
2 times faster than the orc optimized one and would be chosen for all
RGB -> YUV conversions and some YUV->YUV and RGB->RGB conversions.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=732186

gst-libs/gst/video/video-converter.c

@@ -111,6 +111,10 @@ struct _MatrixData
   guint64 orc_p2;
   guint64 orc_p3;
   guint64 orc_p4;
+  gint64 *t_r;
+  gint64 *t_g;
+  gint64 *t_b;
+  gint64 t_c;
   void (*matrix_func) (MatrixData * data, gpointer pixels);
 };
 
@@ -906,6 +910,32 @@ color_matrix_RGB_to_XYZ (MatrixData * dst, double Rx, double Ry, double Gx,
   color_matrix_copy (dst, &m);
 }
 
+static void
+videoconvert_convert_init_tables (MatrixData * data)
+{
+  gint i, j;
+
+  data->t_r = g_new (gint64, 256);
+  data->t_g = g_new (gint64, 256);
+  data->t_b = g_new (gint64, 256);
+
+  for (i = 0; i < 256; i++) {
+    gint64 r = 0, g = 0, b = 0;
+
+    for (j = 0; j < 3; j++) {
+      r = (r << 16) + data->im[j][0] * i;
+      g = (g << 16) + data->im[j][1] * i;
+      b = (b << 16) + data->im[j][2] * i;
+    }
+    data->t_r[i] = r;
+    data->t_g[i] = g;
+    data->t_b[i] = b;
+  }
+  data->t_c = ((gint64) data->im[0][3] << 32)
+      + ((gint64) data->im[1][3] << 16)
+      + ((gint64) data->im[2][3] << 0);
+}
+
 void
 _custom_video_orc_matrix8 (guint8 * ORC_RESTRICT d1,
     const guint8 * ORC_RESTRICT s1, orc_int64 p1, orc_int64 p2, orc_int64 p3,
@@ -953,6 +983,28 @@ video_converter_matrix8 (MatrixData * data, gpointer pixels)
       data->orc_p3, data->orc_p4, data->width);
 }
 
+static void
+video_converter_matrix8_table (MatrixData * data, gpointer pixels)
+{
+  gint i, width = data->width * 4;
+  guint8 r, g, b;
+  gint64 c = data->t_c;
+  guint8 *p = pixels;
+  gint64 x;
+
+  for (i = 0; i < width; i += 4) {
+    r = p[i + 1];
+    g = p[i + 2];
+    b = p[i + 3];
+
+    x = data->t_r[r] + data->t_g[g] + data->t_b[b] + c;
+
+    p[i + 1] = x >> (32 + SCALE);
+    p[i + 2] = x >> (16 + SCALE);
+    p[i + 3] = x >> (0 + SCALE);
+  }
+}
+
 static void
 video_converter_matrix8_AYUV_ARGB (MatrixData * data, gpointer pixels)
 {
@@ -1001,6 +1053,43 @@ is_identity_matrix (MatrixData * data)
   return TRUE;
 }
 
+static gboolean
+is_no_clip_matrix (MatrixData * data)
+{
+  gint i;
+  static const guint8 test[8][3] = {
+    {0, 0, 0},
+    {0, 0, 255},
+    {0, 255, 0},
+    {0, 255, 255},
+    {255, 0, 0},
+    {255, 0, 255},
+    {255, 255, 0},
+    {255, 255, 255}
+  };
+
+  for (i = 0; i < 8; i++) {
+    gint r, g, b;
+    gint y, u, v;
+
+    r = test[i][0];
+    g = test[i][1];
+    b = test[i][2];
+
+    y = (data->im[0][0] * r + data->im[0][1] * g +
+        data->im[0][2] * b + data->im[0][3]) >> SCALE;
+    u = (data->im[1][0] * r + data->im[1][1] * g +
+        data->im[1][2] * b + data->im[1][3]) >> SCALE;
+    v = (data->im[2][0] * r + data->im[2][1] * g +
+        data->im[2][2] * b + data->im[2][3]) >> SCALE;
+
+    if (y != CLAMP (y, 0, 255) || u != CLAMP (u, 0, 255)
+        || v != CLAMP (v, 0, 255))
+      return FALSE;
+  }
+  return TRUE;
+}
+
 static void
 video_converter_matrix16 (MatrixData * data, gpointer pixels)
 {
@@ -1045,6 +1134,10 @@ prepare_matrix (GstVideoConverter * convert, MatrixData * data)
         && is_ayuv_to_rgb_matrix (data)) {
       GST_DEBUG ("use fast AYUV -> RGB matrix");
       data->matrix_func = video_converter_matrix8_AYUV_ARGB;
+    } else if (is_no_clip_matrix (data)) {
+      GST_DEBUG ("use 8bit table");
+      data->matrix_func = video_converter_matrix8_table;
+      videoconvert_convert_init_tables (data);
     } else {
       gint a03, a13, a23;
 
@@ -2091,6 +2184,14 @@ no_pack_func:
   }
 }
 
+static void
+clear_matrix_data (MatrixData * data)
+{
+  g_free (data->t_r);
+  g_free (data->t_g);
+  g_free (data->t_b);
+}
+
 /**
  * gst_video_converter_free:
  * @convert: a #GstVideoConverter
@@ -2160,6 +2261,9 @@ gst_video_converter_free (GstVideoConverter * convert)
     if (convert->fh_scaler[i])
       gst_video_scaler_free (convert->fh_scaler[i]);
   }
+  clear_matrix_data (&convert->to_RGB_matrix);
+  clear_matrix_data (&convert->convert_matrix);
+  clear_matrix_data (&convert->to_YUV_matrix);
 
   g_slice_free (GstVideoConverter, convert);
 }