vp9_bitstream: Encode tiles in parallel

Re-use the tile worker threads to pack the bitstream in parallel
on a per-tile basis.  Restricting this to real-time only for now
(further testing is needed to ensure this does not make 2-pass
worse in any case).

BUG=webm:1309

Change-Id: Ia2c982da56697756e12f02643f589189b3271d98

4 files changed, 145 insertions, 2 deletions

diff --git a/vp9/encoder/vp9_bitstream.c b/vp9/encoder/vp9_bitstream.c
index 22b28de83..048bdb771 100644
--- a/vp9/encoder/vp9_bitstream.c
+++ b/vp9/encoder/vp9_bitstream.c
@@ -915,6 +915,120 @@ int vp9_get_refresh_mask(VP9_COMP *cpi) {
   }
 }
 
+static int encode_tile_worker(VP9_COMP *cpi, VP9BitstreamWorkerData *data) {
+  MACROBLOCKD *const xd = &data->xd;
+  vpx_start_encode(&data->bit_writer, data->dest);
+  write_modes(cpi, xd, &cpi->tile_data[data->tile_idx].tile_info,
+              &data->bit_writer, &data->tok, data->tok_end,
+              &data->max_mv_magnitude, data->interp_filter_selected);
+  assert(data->tok == data->tok_end);
+  vpx_stop_encode(&data->bit_writer);
+  return 1;
+}
+
+void vp9_bitstream_encode_tiles_buffer_dealloc(VP9_COMP *const cpi) {
+  if (cpi->vp9_bitstream_worker_data) {
+    int i;
+    for (i = 1; i < cpi->num_workers; ++i) {
+      vpx_free(cpi->vp9_bitstream_worker_data[i].dest);
+    }
+    vpx_free(cpi->vp9_bitstream_worker_data);
+    cpi->vp9_bitstream_worker_data = NULL;
+  }
+}
+
+static int encode_tiles_buffer_alloc(VP9_COMP *const cpi) {
+  int i;
+  cpi->vp9_bitstream_worker_data =
+      vpx_calloc(cpi->num_workers, sizeof(*cpi->vp9_bitstream_worker_data));
+  if (!cpi->vp9_bitstream_worker_data) return 1;
+  for (i = 1; i < cpi->num_workers; ++i) {
+    cpi->vp9_bitstream_worker_data[i].dest_size =
+        cpi->oxcf.width * cpi->oxcf.height;
+    cpi->vp9_bitstream_worker_data[i].dest =
+        vpx_malloc(cpi->vp9_bitstream_worker_data[i].dest_size);
+    if (!cpi->vp9_bitstream_worker_data[i].dest) return 1;
+  }
+  return 0;
+}
+
+static size_t encode_tiles_mt(VP9_COMP *cpi, uint8_t *data_ptr) {
+  const VPxWorkerInterface *const winterface = vpx_get_worker_interface();
+  VP9_COMMON *const cm = &cpi->common;
+  const int tile_cols = 1 << cm->log2_tile_cols;
+  const int num_workers = cpi->num_workers;
+  size_t total_size = 0;
+  int tile_col = 0;
+
+  if (!cpi->vp9_bitstream_worker_data ||
+      cpi->vp9_bitstream_worker_data[1].dest_size >
+          (cpi->oxcf.width * cpi->oxcf.height)) {
+    vp9_bitstream_encode_tiles_buffer_dealloc(cpi);
+    if (encode_tiles_buffer_alloc(cpi)) return 0;
+  }
+
+  while (tile_col < tile_cols) {
+    int i, j;
+    for (i = 0; i < num_workers && tile_col < tile_cols; ++i) {
+      VPxWorker *const worker = &cpi->workers[i];
+      VP9BitstreamWorkerData *const data = &cpi->vp9_bitstream_worker_data[i];
+
+      // Populate the worker data.
+      data->xd = cpi->td.mb.e_mbd;
+      data->tile_idx = tile_col;
+      data->tok = cpi->tile_tok[0][tile_col];
+      data->tok_end = cpi->tile_tok[0][tile_col] + cpi->tok_count[0][tile_col];
+      data->max_mv_magnitude = cpi->max_mv_magnitude;
+      memset(data->interp_filter_selected, 0,
+             sizeof(data->interp_filter_selected[0][0]) * SWITCHABLE);
+
+      // First thread can directly write into the output buffer.
+      if (i == 0) {
+        data->dest = data_ptr + total_size + 4;
+      }
+      worker->data1 = cpi;
+      worker->data2 = data;
+      worker->hook = (VPxWorkerHook)encode_tile_worker;
+      worker->had_error = 0;
+
+      if (i < num_workers - 1) {
+        winterface->launch(worker);
+      } else {
+        winterface->execute(worker);
+      }
+      ++tile_col;
+    }
+    for (j = 0; j < i; ++j) {
+      VPxWorker *const worker = &cpi->workers[j];
+      VP9BitstreamWorkerData *const data =
+          (VP9BitstreamWorkerData *)worker->data2;
+      uint32_t tile_size;
+      int k;
+
+      if (!winterface->sync(worker)) return 0;
+      tile_size = data->bit_writer.pos;
+
+      // Aggregate per-thread bitstream stats.
+      cpi->max_mv_magnitude =
+          VPXMAX(cpi->max_mv_magnitude, data->max_mv_magnitude);
+      for (k = 0; k < SWITCHABLE; ++k) {
+        cpi->interp_filter_selected[0][k] += data->interp_filter_selected[0][k];
+      }
+
+      // Prefix the size of the tile on all but the last.
+      if (tile_col != tile_cols || j < i - 1) {
+        mem_put_be32(data_ptr + total_size, tile_size);
+        total_size += 4;
+      }
+      if (j > 0) {
+        memcpy(data_ptr + total_size, data->dest, tile_size);
+      }
+      total_size += tile_size;
+    }
+  }
+  return total_size;
+}
+
 static size_t encode_tiles(VP9_COMP *cpi, uint8_t *data_ptr) {
   VP9_COMMON *const cm = &cpi->common;
   MACROBLOCKD *const xd = &cpi->td.mb.e_mbd;
@@ -928,6 +1042,14 @@ static size_t encode_tiles(VP9_COMP *cpi, uint8_t *data_ptr) {
   memset(cm->above_seg_context, 0,
          sizeof(*cm->above_seg_context) * mi_cols_aligned_to_sb(cm->mi_cols));
 
+  // Encoding tiles in parallel is done only for realtime mode now. In other
+  // modes the speed up is insignificant and requires further testing to ensure
+  // that it does not make the overall process worse in any case.
+  if (cpi->oxcf.mode == REALTIME && cpi->num_workers > 1 && tile_rows == 1 &&
+      tile_cols > 1) {
+    return encode_tiles_mt(cpi, data_ptr);
+  }
+
   for (tile_row = 0; tile_row < tile_rows; tile_row++) {
     for (tile_col = 0; tile_col < tile_cols; tile_col++) {
       int tile_idx = tile_row * tile_cols + tile_col;
@@ -955,7 +1077,6 @@ static size_t encode_tiles(VP9_COMP *cpi, uint8_t *data_ptr) {
       total_size += residual_bc.pos;
     }
   }
-
   return total_size;
 }
 
diff --git a/vp9/encoder/vp9_bitstream.h b/vp9/encoder/vp9_bitstream.h
index 8c97d37f7..c669d7145 100644
--- a/vp9/encoder/vp9_bitstream.h
+++ b/vp9/encoder/vp9_bitstream.h
@@ -17,10 +17,28 @@ extern "C" {
 
 #include "vp9/encoder/vp9_encoder.h"
 
+typedef struct VP9BitstreamWorkerData {
+  uint8_t *dest;
+  int dest_size;
+  TOKENEXTRA *tok;
+  TOKENEXTRA *tok_end;
+  vpx_writer bit_writer;
+  int tile_idx;
+  unsigned int max_mv_magnitude;
+  // The size of interp_filter_selected in VP9_COMP is actually
+  // MAX_REFERENCE_FRAMES x SWITCHABLE. But when encoding tiles, all we ever do
+  // is increment the very first index (index 0) for the first dimension. Hence
+  // this is sufficient.
+  int interp_filter_selected[1][SWITCHABLE];
+  DECLARE_ALIGNED(16, MACROBLOCKD, xd);
+} VP9BitstreamWorkerData;
+
 int vp9_get_refresh_mask(VP9_COMP *cpi);
 
 void vp9_pack_bitstream(VP9_COMP *cpi, uint8_t *dest, size_t *size);
 
+void vp9_bitstream_encode_tiles_buffer_dealloc(VP9_COMP *const cpi);
+
 static INLINE int vp9_preserve_existing_gf(VP9_COMP *cpi) {
   return !cpi->multi_arf_allowed && cpi->refresh_golden_frame &&
          cpi->rc.is_src_frame_alt_ref &&
diff --git a/vp9/encoder/vp9_encoder.c b/vp9/encoder/vp9_encoder.c
index d98c4938e..43b708be8 100644
--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -2030,7 +2030,10 @@ void vp9_remove_compressor(VP9_COMP *cpi) {
   vpx_free(cpi->tile_thr_data);
   vpx_free(cpi->workers);
 
-  if (cpi->num_workers > 1) vp9_loop_filter_dealloc(&cpi->lf_row_sync);
+  if (cpi->num_workers > 1) {
+    vp9_loop_filter_dealloc(&cpi->lf_row_sync);
+    vp9_bitstream_encode_tiles_buffer_dealloc(cpi);
+  }
 
   vp9_alt_ref_aq_destroy(cpi->alt_ref_aq);
 
diff --git a/vp9/encoder/vp9_encoder.h b/vp9/encoder/vp9_encoder.h
index 77eb31cb3..e353d4779 100644
--- a/vp9/encoder/vp9_encoder.h
+++ b/vp9/encoder/vp9_encoder.h
@@ -601,6 +601,7 @@ typedef struct VP9_COMP {
   VPxWorker *workers;
   struct EncWorkerData *tile_thr_data;
   VP9LfSync lf_row_sync;
+  struct VP9BitstreamWorkerData *vp9_bitstream_worker_data;
 
   int keep_level_stats;
   Vp9LevelInfo level_info;