Optimize the buffer usage for 180 degrees rotation

When the system is extremely slow, the buffer allocation of the output
buffer can fail and upper layer would get the raw un-rotated buffer.

This CL mitigates the issue by reusing the original buffer for 180
degrees rotate, which is the default orientation of the user facing
camera on Nocturne.

Bug: 1061346
Test: Run Hangouts Meet with screen rotated with 0, 90, 180, 270
degrees.

Change-Id: I7051fa9e0c3857345ff3ad1916fd3d91d6a59f71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2101324Reviewed-by: Ricky Liang <jcliang@chromium.org>
Commit-Queue: Shik Chen <shik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750487}

media/capture/video/chromeos/stream_buffer_manager.cc

@@ -88,39 +88,24 @@ StreamBufferManager::AcquireBufferForClientById(StreamType stream_type,
     format->frame_size =
         gfx::Size(format->frame_size.height(), format->frame_size.width());
   }
-  Buffer rotated_buffer;
-  if (!device_context_->ReserveVideoCaptureBufferFromPool(
-          format->frame_size, format->pixel_format, &rotated_buffer)) {
-    DLOG(WARNING) << "Failed to reserve video capture buffer";
-    return std::move(buffer_pair.vcd_buffer);
-  }
 
   base::Optional<gfx::BufferFormat> gfx_format =
       PixFormatVideoToGfx(format->pixel_format);
   DCHECK(gfx_format);
-  auto rotated_gmb = gmb_support_->CreateGpuMemoryBufferImplFromHandle(
-      rotated_buffer.handle_provider->GetGpuMemoryBufferHandle(),
-      format->frame_size, *gfx_format,
-      CameraBufferFactory::GetBufferUsage(*gfx_format), base::NullCallback());
-
-  if (!rotated_gmb || !rotated_gmb->Map()) {
-    DLOG(WARNING) << "Failed to map rotated buffer";
-    return std::move(buffer_pair.vcd_buffer);
-  }
   const auto& original_gmb = buffer_pair.gmb;
   if (!original_gmb->Map()) {
     DLOG(WARNING) << "Failed to map original buffer";
-    rotated_gmb->Unmap();
     return std::move(buffer_pair.vcd_buffer);
   }
 
   const size_t original_width = stream_context->buffer_dimension.width();
   const size_t original_height = stream_context->buffer_dimension.height();
-  const size_t temp_buffer_size =
-      ((original_width + 1) & ~1) * ((original_height + 1) & ~1) / 2;
-  std::vector<uint8_t> temp_uv_buffer(temp_buffer_size);
+  const size_t temp_uv_width = (original_width + 1) / 2;
+  const size_t temp_uv_height = (original_height + 1) / 2;
+  const size_t temp_uv_size = temp_uv_width * temp_uv_height;
+  std::vector<uint8_t> temp_uv_buffer(temp_uv_size * 2);
   uint8_t* temp_u = temp_uv_buffer.data();
-  uint8_t* temp_v = temp_uv_buffer.data() + (temp_buffer_size / 2);
+  uint8_t* temp_v = temp_u + temp_uv_size;
 
   // libyuv currently provides only NV12ToI420Rotate. We achieve NV12 rotation
   // by NV12ToI420Rotate then merge the I420 U and V planes into the final NV12
@@ -138,22 +123,59 @@ StreamBufferManager::AcquireBufferForClientById(StreamType stream_type,
     }
     return libyuv::kRotate0;
   };
-  const size_t temp_chroma_width = (rotated_gmb->GetSize().width() + 1) / 2;
-  const size_t temp_chroma_height = (rotated_gmb->GetSize().height() + 1) / 2;
-  libyuv::NV12ToI420Rotate(
-      static_cast<uint8_t*>(original_gmb->memory(0)), original_gmb->stride(0),
-      static_cast<uint8_t*>(original_gmb->memory(1)), original_gmb->stride(1),
-      static_cast<uint8_t*>(rotated_gmb->memory(0)), rotated_gmb->stride(0),
-      temp_u, temp_chroma_width, temp_v, temp_chroma_width, original_width,
-      original_height, translate_rotation(rotation));
-  libyuv::MergeUVPlane(temp_u, temp_chroma_width, temp_v, temp_chroma_width,
-                       static_cast<uint8_t*>(rotated_gmb->memory(1)),
-                       rotated_gmb->stride(1), temp_chroma_width,
-                       temp_chroma_height);
-
-  rotated_gmb->Unmap();
-  original_gmb->Unmap();
-  return std::move(rotated_buffer);
+
+  if (rotation == 180) {
+    // We can reuse the original buffer in this case because the size is same.
+    // Note that libyuv can in-place rotate the Y-plane by 180 degrees.
+    libyuv::NV12ToI420Rotate(
+        static_cast<uint8_t*>(original_gmb->memory(0)), original_gmb->stride(0),
+        static_cast<uint8_t*>(original_gmb->memory(1)), original_gmb->stride(1),
+        static_cast<uint8_t*>(original_gmb->memory(0)), original_gmb->stride(0),
+        temp_u, temp_uv_width, temp_v, temp_uv_width, original_width,
+        original_height, translate_rotation(rotation));
+    libyuv::MergeUVPlane(temp_u, temp_uv_width, temp_v, temp_uv_width,
+                         static_cast<uint8_t*>(original_gmb->memory(1)),
+                         original_gmb->stride(1), temp_uv_width,
+                         temp_uv_height);
+    original_gmb->Unmap();
+    return std::move(buffer_pair.vcd_buffer);
+  } else {
+    // We have to reserve a new buffer because the size is different.
+    Buffer rotated_buffer;
+    if (!device_context_->ReserveVideoCaptureBufferFromPool(
+            format->frame_size, format->pixel_format, &rotated_buffer)) {
+      DLOG(WARNING) << "Failed to reserve video capture buffer";
+      original_gmb->Unmap();
+      return std::move(buffer_pair.vcd_buffer);
+    }
+
+    base::Optional<gfx::BufferFormat> gfx_format =
+        PixFormatVideoToGfx(format->pixel_format);
+    DCHECK(gfx_format);
+    auto rotated_gmb = gmb_support_->CreateGpuMemoryBufferImplFromHandle(
+        rotated_buffer.handle_provider->GetGpuMemoryBufferHandle(),
+        format->frame_size, *gfx_format,
+        CameraBufferFactory::GetBufferUsage(*gfx_format), base::NullCallback());
+
+    if (!rotated_gmb || !rotated_gmb->Map()) {
+      DLOG(WARNING) << "Failed to map rotated buffer";
+      original_gmb->Unmap();
+      return std::move(buffer_pair.vcd_buffer);
+    }
+
+    libyuv::NV12ToI420Rotate(
+        static_cast<uint8_t*>(original_gmb->memory(0)), original_gmb->stride(0),
+        static_cast<uint8_t*>(original_gmb->memory(1)), original_gmb->stride(1),
+        static_cast<uint8_t*>(rotated_gmb->memory(0)), rotated_gmb->stride(0),
+        temp_u, temp_uv_height, temp_v, temp_uv_height, original_width,
+        original_height, translate_rotation(rotation));
+    libyuv::MergeUVPlane(temp_u, temp_uv_height, temp_v, temp_uv_height,
+                         static_cast<uint8_t*>(rotated_gmb->memory(1)),
+                         rotated_gmb->stride(1), temp_uv_height, temp_uv_width);
+    rotated_gmb->Unmap();
+    original_gmb->Unmap();
+    return std::move(rotated_buffer);
+  }
 }
 
 VideoCaptureFormat StreamBufferManager::GetStreamCaptureFormat(