Add vp9 QP parser.

webrtc/modules/video_coding/utility/vp9_uncompressed_header_parser.cc

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "webrtc/modules/video_coding/utility/vp9_uncompressed_header_parser.h"
+
+namespace webrtc {
+
+namespace vp9 {
+namespace {
+const size_t kVp9MaxProfile = 4;
+const size_t kVp9NumRefsPerFrame = 3;
+const size_t kVp9MaxRefLFDeltas = 4;
+const size_t kVp9MaxModeLFDeltas = 2;
+}  // namespace
+
+static uint8_t VP9ReadProfile(VP9BitReader* const br) {

[brandtr, 2017/05/22 18:34:56]

I think you can drop the const here, and in the signatures below.

[jianj1, 2017/05/22 21:18:57]

Done.

+  uint8_t profile = 0;
+  if (br->GetBit())
+    profile |= 1;
+  if (br->GetBit())
+    profile |= 2;
+  if (profile > 2 && br->GetBit())
+    profile += 1;
+  return profile;
+}
+
+static bool VP9ReadColorConfig(VP9BitReader* const br, const uint8_t profile) {
+  if (profile == 2 || profile == 3) {
+    // bitdepth

[brandtr, 2017/05/22 18:34:56]

Nit: start comments with capital and end with period. Here and below.

[jianj1, 2017/05/22 21:18:57]

Done.

+    br->GetBit();
+  }
+
+  uint8_t color_space = br->GetValue(3);
+  // SRGB is 7
+  if (color_space != 7) {
+    // yuv range flag
+    br->GetBit();
+    if (profile == 1 || profile == 3) {
+      // Subsampling x.
+      br->GetBit();
+      // Subsampling y.
+      br->GetBit();
+      // Reserved.
+      if (br->GetBit()) {
+        LOG(LS_WARNING) << "Failed to get QP. Reserved bit set.";
+        return false;
+      }
+    }
+  } else {
+    if (profile == 1 || profile == 3) {
+      // Reserved.
+      if (br->GetBit()) {
+        LOG(LS_WARNING) << "Failed to get QP. Reserved bit set.";
+        return false;
+      }
+    } else {
+      LOG(LS_WARNING) << "Failed to get QP. 4:4:4 color not supported in "
+                         "profile 0 or 2.";
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static void VP9ReadFrameSize(VP9BitReader* const br) {
+  // Frame width.
+  uint32_t width = br->GetValue(16);

[brandtr, 2017/05/22 18:34:56]

I think you could drop the comments, or drop the variables altogether but keep
the comments?

[jianj1, 2017/05/22 21:18:57]

Done.

+  (void)width;
+  // Frame height.
+  uint32_t height = br->GetValue(16);
+  (void)height;
+}
+
+static void VP9ReadRenderSize(VP9BitReader* const br) {
+  // Scaling.
+  if (br->GetBit()) {
+    // Render width.
+    uint32_t width = br->GetValue(16);
+    // Render height.
+    uint32_t height = br->GetValue(16);
+    (void)width;
+    (void)height;
+  }
+}
+
+static void VP9ReadFrameSizeFromRefs(VP9BitReader* const br) {
+  int found_ref = 0;
+  for (size_t i = 0; i < kVp9NumRefsPerFrame; i++) {
+    // Size in refs.
+    found_ref = br->GetBit();
+    if (found_ref)
+      break;
+  }
+
+  if (!found_ref)
+    VP9ReadFrameSize(br);
+
+  VP9ReadRenderSize(br);
+}
+
+static void VP9ReadInterpolationFilter(VP9BitReader* const br) {
+  if (br->GetBit())
+    return;
+
+  br->GetValue(2);
+}
+
+static void VP9ReadLoopfilter(VP9BitReader* const br) {
+  // Filter level.
+  br->GetValue(6);
+  // Sharpness level.
+  br->GetValue(3);
+  uint32_t mode_ref_delta_enabled = br->GetBit();
+  if (mode_ref_delta_enabled) {
+    uint32_t mode_ref_delta_update = br->GetBit();
+    if (mode_ref_delta_update) {
+      for (size_t i = 0; i < kVp9MaxRefLFDeltas; i++) {
+        if (br->GetBit())
+          br->GetSignedValue(6);
+      }
+      for (size_t i = 0; i < kVp9MaxModeLFDeltas; i++) {
+        if (br->GetBit())
+          br->GetSignedValue(6);
+      }
+    }
+  }
+}
+
+bool GetQp(const uint8_t* buf, size_t length, int* qp) {
+  VP9BitReader br(buf, length);
+  // VP9InitBitReader(&br, buf, buf + length);

[brandtr, 2017/05/22 18:34:56]

Remove?

[jianj1, 2017/05/22 21:18:57]

Done.

+
+  // Frame marker.
+  if (br.GetValue(2) != 0x2) {
+    LOG(LS_WARNING) << "Failed to get QP. Frame marker should be 2.";
+    return false;
+  }
+
+  // Profile.
+  uint8_t profile = VP9ReadProfile(&br);
+  if (profile > kVp9MaxProfile) {
+    LOG(LS_WARNING) << "Failed to get QP. Unsupported bitstream profile: "
+                    << profile;
+    return false;
+  }
+
+  // Show existing frame.
+  if (br.GetBit()) {
+    br.GetValue(3);

[brandtr, 2017/05/22 18:34:56]

Is this row needed when you return below?

[jianj1, 2017/05/22 21:18:57]

Done.

+    return false;
+  }
+
+  // Frame type: KEY_FRAME(0), INTER_FRAME(1).
+  uint8_t frame_type = br.GetBit();
+  // Show frame.
+  uint8_t show_frame = br.GetBit();
+  // Error resilient.
+  uint8_t error_resilient = br.GetBit();
+
+  if (!frame_type) {
+    // Sync code.
+    uint32_t sync_code = br.GetValue(24);
+    if (sync_code != 0x498342) {
+      LOG(LS_WARNING) << "Failed to get QP. Invalid sync code.";
+      return false;
+    }
+
+    if (!VP9ReadColorConfig(&br, profile))
+      return false;
+
+    VP9ReadFrameSize(&br);
+    VP9ReadRenderSize(&br);
+  } else {
+    uint8_t intra_only = 0;
+    if (!show_frame)
+      intra_only = br.GetBit();
+
+    if (!error_resilient)
+      // Reset frame context.
+      br.GetValue(2);
+
+    if (intra_only) {
+      // Sync code.
+      if (br.GetValue(24) != 0x498342) {
+        LOG(LS_WARNING) << "Failed to get QP. Invalid sync code.";
+        return false;
+      }
+      if (profile > 0) {
+        if (!VP9ReadColorConfig(&br, profile))
+          return false;
+      }
+      // Refresh frame flags.
+      br.GetValue(8);
+
+      VP9ReadFrameSize(&br);
+      VP9ReadRenderSize(&br);
+    } else {
+      // Refresh frame flags.
+      int32_t test = br.GetValue(8);
+      (void)test;
+
+      for (size_t i = 0; i < kVp9NumRefsPerFrame; i++) {

[brandtr, 2017/05/22 18:34:56]

Maybe move this to its own function too?

[jianj1, 2017/05/22 21:18:57]

Done.

It's probably better to keep it here since the logic is the same as the
bitstream manual. It would be easier to maintain and look back in the future.

[brandtr, 2017/05/23 08:59:02]

Makes sense. Thanks.

+        // Ref frame index.
+        int32_t idx = br.GetValue(3);
+        // Ref frame sign biases.
+        int32_t bias = br.GetBit();
+        (void)idx;
+        (void)bias;
+      }
+
+      VP9ReadFrameSizeFromRefs(&br);
+      // Allow high precision mv.
+      br.GetBit();
+      // Interpolation filter.
+      VP9ReadInterpolationFilter(&br);
+    }
+  }
+
+  if (!error_resilient) {
+    // Refresh frame context.
+    br.GetBit();
+    // Frame parallel decoding mode.
+    br.GetBit();
+  }
+
+  // Frame context index.
+  br.GetValue(2);
+
+  VP9ReadLoopfilter(&br);
+
+  // Base QP.
+  const int base_q0 = br.GetValue(8);
+  *qp = base_q0;
+  return true;
+}
+
+}  // namespace vp9
+
+}  // namespace webrtc