Add command line arguments for tiling

Add --tile-cols-log2 and --tile-rows-log2 to configure tiling.

This configuration is made available in FrameInvariants.

src/api.rs

@@ -75,6 +75,8 @@ pub struct EncoderConfig {
   pub quantizer: usize,
   pub bitrate: i32,
   pub tune: Tune,
+  pub tile_cols_log2: usize,
+  pub tile_rows_log2: usize,
   pub speed_settings: SpeedSettings,
   /// `None` for one-pass encode. `Some(1)` or `Some(2)` for two-pass encoding.
   pub pass: Option<u8>,
@@ -111,6 +113,8 @@ impl EncoderConfig {
       quantizer: 100,
       bitrate: 0,
       tune: Tune::default(),
+      tile_cols_log2: 0,
+      tile_rows_log2: 0,
       speed_settings: SpeedSettings::from_preset(speed),
       pass: None,
       show_psnr: false,

src/bin/common.rs

@@ -174,6 +174,20 @@ pub fn parse_cli() -> CliOptions {
         .default_value("Psychovisual")
         .case_insensitive(true)
     )
+    .arg(
+      Arg::with_name("TILE_ROWS_LOG2")
+        .help("Log2 of number of tile rows")
+        .long("tile-rows-log2")
+        .takes_value(true)
+        .default_value("0")
+    )
+    .arg(
+      Arg::with_name("TILE_COLS_LOG2")
+        .help("Log2 of number of tile columns")
+        .long("tile-cols-log2")
+        .takes_value(true)
+        .default_value("0")
+    )
     // MASTERING
     .arg(
       Arg::with_name("PIXEL_RANGE")
@@ -426,6 +440,14 @@ fn parse_config(matches: &ArgMatches<'_>) -> EncoderConfig {
     None
   };
   cfg.tune = matches.value_of("TUNE").unwrap().parse().unwrap();
+
+  cfg.tile_cols_log2 = matches.value_of("TILE_COLS_LOG2").unwrap().parse().unwrap();
+  cfg.tile_rows_log2 = matches.value_of("TILE_ROWS_LOG2").unwrap().parse().unwrap();
+
+  if cfg.tile_cols_log2 > 6 || cfg.tile_rows_log2 > 6 {
+    panic!("Log2 of tile columns and rows may not be greater than 6");
+  }
+
   cfg.low_latency = matches.value_of("LOW_LATENCY").unwrap().parse().unwrap();
   cfg.train_rdo = train_rdo;
   cfg