12-bit vp9 video support

cc/resources/video_resource_updater.cc

Index: cc/resources/video_resource_updater.cc
diff --git a/cc/resources/video_resource_updater.cc b/cc/resources/video_resource_updater.cc
index 2584e0b3a83308af23ac83893c244a9badc04111..c83c5f6137443336cbe7d452e2cacda0436e6056 100644
--- a/cc/resources/video_resource_updater.cc
+++ b/cc/resources/video_resource_updater.cc
@@ -84,6 +84,9 @@ VideoFrameExternalResources::ResourceType ResourceTypeForVideoFrame(
     case media::PIXEL_FORMAT_YUV420P10:
     case media::PIXEL_FORMAT_YUV422P10:
     case media::PIXEL_FORMAT_YUV444P10:
+    case media::PIXEL_FORMAT_YUV420P12:
+    case media::PIXEL_FORMAT_YUV422P12:
+    case media::PIXEL_FORMAT_YUV444P12:
     case media::PIXEL_FORMAT_UNKNOWN:
       break;
   }
@@ -289,6 +292,23 @@ static gfx::Size SoftwarePlaneDimension(media::VideoFrame* input_frame,
   return gfx::Size(plane_width, plane_height);
 }
 
+// Values are expected to be in [0.0..1.0]
+void VideoResourceUpdater::MakeHalfFloats(const uint16_t* src,
+                                          float mult,
+                                          size_t num,
+                                          uint16_t* dst) {
+  // TODO(hubbe): Make AVX and neon versions of this code.
+  mult *= 1.9259299444e-34f;  // Magic conversion value.
+  for (size_t i = 0; i < num; i++) {
+    if (src[i] == 0) {
+      dst[i] = 0;
+    } else {
+      float value = src[i] * mult;
+      dst[i] = (*(uint32_t*)&value) >> 13;
+    }
+  }
+}
+
 VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
     scoped_refptr<media::VideoFrame> video_frame) {
   TRACE_EVENT0("cc", "VideoResourceUpdater::CreateForSoftwarePlanes");
@@ -327,6 +347,11 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
     case media::PIXEL_FORMAT_YUV444P10:
       bits_per_channel = 10;
       break;
+    case media::PIXEL_FORMAT_YUV420P12:
+    case media::PIXEL_FORMAT_YUV422P12:
+    case media::PIXEL_FORMAT_YUV444P12:
+      bits_per_channel = 12;
+      break;
   }
 
   // Only YUV software video frames are supported.
@@ -484,7 +509,6 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
         needs_conversion = true;
         // Note that the current method of converting integers to half-floats

[danakj, 2016/09/26 20:35:04]

What about this comment?

[hubbe, 2016/09/26 21:19:36]

Removed.

         // stops working if you have more than 10 bits of data.
-        DCHECK_LE(bits_per_channel, 10);
       } else if (bits_per_channel > 8) {
         // If bits_per_channel > 8 and we can't use LUMINANCE_F16, we need to
         // shift the data down and create an 8-bit texture.
@@ -508,13 +532,18 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
                 &upload_pixels_[upload_image_stride * row]);
             const uint16_t* src = reinterpret_cast<uint16_t*>(
                 video_frame->data(i) + (video_stride_bytes * row));
-            // Micro-benchmarking indicates that the compiler does
-            // a good enough job of optimizing this loop that trying
-            // to manually operate on one uint64 at a time is not
-            // actually helpful.
-            // Note to future optimizers: Benchmark your optimizations!
-            for (size_t i = 0; i < bytes_per_row / 2; i++)
-              dst[i] = src[i] | 0x3800;
+            if (bits_per_channel <= 10) {
+              // Micro-benchmarking indicates that the compiler does
+              // a good enough job of optimizing this loop that trying
+              // to manually operate on one uint64 at a time is not
+              // actually helpful.
+              // Note to future optimizers: Benchmark your optimizations!
+              for (size_t i = 0; i < bytes_per_row / 2; i++)
+                dst[i] = src[i] | 0x3800;
+            } else {
+              MakeHalfFloats(src, 1.0f / ((1 << bits_per_channel) - 1),
+                             bytes_per_row / 2, dst);
+            }
           } else if (shift != 0) {
             // We have more-than-8-bit input which we need to shift
             // down to fit it into an 8-bit texture.
@@ -540,7 +569,8 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
       plane_resource.SetUniqueId(video_frame->unique_id(), i);
     }
 
-    if (plane_resource.resource_format() == LUMINANCE_F16) {
+    if (plane_resource.resource_format() == LUMINANCE_F16 &&
+        bits_per_channel <= 10) {

[danakj, 2016/09/26 20:35:04]

what if bits > 10?

[hubbe, 2016/09/26 21:19:36]

Then offset and multiplier should have their default values, because values has
been converted to a half-float between 0.0 and 1.0.

Frank is looking in to making and SSE2 version of the float-to-half-float code,
and if that's fast enough we can get rid of the OR trick and  the
offset/multiplier.

Of course, all of this is moot if we end up using RG88 textures to represent
16-bit values, but we haven't done enough experimentation to see if that is the
best option yet.

[danakj, 2016/09/26 22:10:39]

Can you explain in a comment too?

[hubbe, 2016/09/27 00:03:24]

Done.

       // By OR-ing with 0x3800, 10-bit numbers become half-floats in the
       // range [0.5..1) and 9-bit numbers get the range [0.5..0.75).
       //