VP9 level targeting: add a new AUTO mode

In the new AUTO mode, restrict the minimum alt-ref interval and max column
tiles adaptively based on picture size, while not applying any rate control
constraints.

This mode aims to produce encodings that fit into levels corresponding to
the source picture size, with minimum compression quality lost. However, the
bitstream is not guaranteed to be level compatible, e.g., the average bitrate
may exceed level limit.

BUG=b/64451920

Change-Id: I02080b169cbbef4ab2e08c0df4697ce894aad83c

5 files changed, 46 insertions, 1 deletions

diff --git a/vp9/encoder/vp9_encoder.c b/vp9/encoder/vp9_encoder.c
index 870ba9fce..27bc0188e 100644
--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -1209,6 +1209,14 @@ static void set_tile_limits(VP9_COMP *cpi) {
         clamp(cpi->oxcf.tile_columns, min_log2_tile_cols, max_log2_tile_cols);
     cm->log2_tile_rows = cpi->oxcf.tile_rows;
   }
+
+  if (cpi->oxcf.target_level == LEVEL_AUTO) {
+    const uint32_t pic_size = cpi->common.width * cpi->common.height;
+    const int level_tile_cols = log_tile_cols_from_picsize_level(pic_size);
+    if (cm->log2_tile_cols > level_tile_cols) {
+      cm->log2_tile_cols = VPXMAX(level_tile_cols, min_log2_tile_cols);
+    }
+  }
 }
 
 static void update_frame_size(VP9_COMP *cpi) {
diff --git a/vp9/encoder/vp9_encoder.h b/vp9/encoder/vp9_encoder.h
index d735fe08b..34a175a74 100644
--- a/vp9/encoder/vp9_encoder.h
+++ b/vp9/encoder/vp9_encoder.h
@@ -360,6 +360,7 @@ typedef struct IMAGE_STAT {
 
 typedef enum {
   LEVEL_UNKNOWN = 0,
+  LEVEL_AUTO = 1,
   LEVEL_1 = 10,
   LEVEL_1_1 = 11,
   LEVEL_2 = 20,
@@ -913,6 +914,18 @@ static INLINE int get_level_index(VP9_LEVEL level) {
   return -1;
 }
 
+// Return the log2 value of max column tiles corresponding to the level that
+// the picture size fits into.
+static INLINE int log_tile_cols_from_picsize_level(uint32_t pic_size) {
+  int i;
+  for (i = LEVEL_1; i < LEVEL_MAX; ++i) {
+    if (vp9_level_defs[i].max_luma_picture_size > pic_size) {
+      return get_msb(vp9_level_defs[i].max_col_tiles);
+    }
+  }
+  return INT_MAX;
+}
+
 VP9_LEVEL vp9_get_level(const Vp9LevelSpec *const level_spec);
 
 void vp9_new_framerate(VP9_COMP *cpi, double framerate);
diff --git a/vp9/encoder/vp9_ethread.c b/vp9/encoder/vp9_ethread.c
index 5028eef0f..d182ec765 100644
--- a/vp9/encoder/vp9_ethread.c
+++ b/vp9/encoder/vp9_ethread.c
@@ -64,6 +64,13 @@ static int get_max_tile_cols(VP9_COMP *cpi) {
   vp9_get_tile_n_bits(mi_cols, &min_log2_tile_cols, &max_log2_tile_cols);
   log2_tile_cols =
       clamp(cpi->oxcf.tile_columns, min_log2_tile_cols, max_log2_tile_cols);
+  if (cpi->oxcf.target_level == LEVEL_AUTO) {
+    const uint32_t pic_size = cpi->common.width * cpi->common.height;
+    const int level_tile_cols = log_tile_cols_from_picsize_level(pic_size);
+    if (log2_tile_cols > level_tile_cols) {
+      log2_tile_cols = VPXMAX(level_tile_cols, min_log2_tile_cols);
+    }
+  }
   return (1 << log2_tile_cols);
 }
 
diff --git a/vp9/encoder/vp9_ratectrl.c b/vp9/encoder/vp9_ratectrl.c
index 82e4b1df1..93de41e86 100644
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -1851,6 +1851,23 @@ void vp9_rc_set_gf_interval_range(const VP9_COMP *const cpi,
 
     // Clamp min to max
     rc->min_gf_interval = VPXMIN(rc->min_gf_interval, rc->max_gf_interval);
+
+    if (oxcf->target_level == LEVEL_AUTO) {
+      const uint32_t pic_size = cpi->common.width * cpi->common.height;
+      int i;
+      for (i = LEVEL_1; i < LEVEL_MAX; ++i) {
+        if (vp9_level_defs[i].max_luma_picture_size > pic_size) {
+          if (rc->min_gf_interval <=
+              (int)vp9_level_defs[i].min_altref_distance) {
+            rc->min_gf_interval =
+                (int)vp9_level_defs[i].min_altref_distance + 1;
+            rc->max_gf_interval =
+                VPXMAX(rc->max_gf_interval, rc->min_gf_interval);
+          }
+          break;
+        }
+      }
+    }
   }
 }
 
diff --git a/vp9/vp9_cx_iface.c b/vp9/vp9_cx_iface.c
index 7b6aa4bf5..db18862c7 100644
--- a/vp9/vp9_cx_iface.c
+++ b/vp9/vp9_cx_iface.c
@@ -213,7 +213,7 @@ static vpx_codec_err_t validate_config(vpx_codec_alg_priv_t *ctx,
         level != LEVEL_4 && level != LEVEL_4_1 && level != LEVEL_5 &&
         level != LEVEL_5_1 && level != LEVEL_5_2 && level != LEVEL_6 &&
         level != LEVEL_6_1 && level != LEVEL_6_2 && level != LEVEL_UNKNOWN &&
-        level != LEVEL_MAX)
+        level != LEVEL_AUTO && level != LEVEL_MAX)
       ERROR("target_level is invalid");
   }