Add vp9 QP parser.

webrtc/modules/video_coding/utility/vp9_uncomp_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_uncomp_header_parser.h"
+

[brandtr, 2017/05/19 14:10:27]

General comment: have you looked into using the rtc::BitBuffer here? It might
simplify things.
https://cs.chromium.org/chromium/src/third_party/webrtc/base/bitbuffer.h?l=28...

[jianj1, 2017/05/19 21:20:56]

Done.

+#include "webrtc/base/logging.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 void VP9InitBitReader(VP9BitReader *const br, const uint8_t *const start,

[brandtr, 2017/05/19 14:10:27]

To me, it seems that VP9BitReader could be a full-blown C++ class?

[jianj1, 2017/05/19 21:20:56]

Done.

BTW, the same thing could be done to vp8_header_parser, too. I will upload a new
CL to make two qp parsers consistent.

+                             const uint8_t *const end) {

[brandtr, 2017/05/19 14:10:27]

const uint8_t*, here and in other signatures.

[jianj1, 2017/05/19 21:20:56]

Done.

+  br->offset_ = 0;
+  br->buf_ = start;
+  br->buf_end_ = end;
+}
+
+static int32_t VP9GetBit(VP9BitReader *const br) {
+  const size_t off = br->offset_;
+  const size_t p = off >> 3;
+  const int q = 7 - static_cast<int>(off & 0x7);
+  if (br->buf_ + p < br->buf_end_) {
+    const int bit = (br->buf_[p] >> q) & 1;
+    br->offset_ = off + 1;
+    return bit;
+  } else {
+    LOG(LS_WARNING) << "Failed to get QP. Reached EOF.";
+    return 0;
+  }
+}
+
+static int32_t VP9GetValue(VP9BitReader *const br, int bits) {
+  int value = 0, bit;
+  for (bit = bits - 1; bit >= 0; bit--)
+    value |= VP9GetBit(br) << bit;
+  return value;
+}
+
+static int32_t VP9GetSignedValue(VP9BitReader *const br, int bits) {
+  const int value = VP9GetValue(br, bits);
+  return VP9GetBit(br) ? -value : value;
+}
+
+static uint8_t VP9ReadProfile(VP9BitReader *const br) {
+  uint8_t profile = 0;
+  if (VP9GetBit(br))
+    profile |= 1;
+  if (VP9GetBit(br))
+    profile |= 2;
+  if (profile > 2 && VP9GetBit(br))
+    profile += 1;
+  return profile;
+}
+
+static bool VP9ReadColorConfig(VP9BitReader *const br, const uint8_t profile) {
+  if (profile == 2 || profile == 3) {
+    // bitdepth
+    VP9GetBit(br);
+  }
+
+  uint8_t color_space = VP9GetValue(br, 3);
+  // SRGB is 7
+  if (color_space != 7) {
+    // yuv range flag
+    VP9GetBit(br);
+    if (profile == 1 || profile == 3) {
+      // subsampling x

[brandtr, 2017/05/19 14:10:27]

Comments: start with capital letter and end with period.

[jianj1, 2017/05/19 21:20:56]

Done.

+      VP9GetBit(br);
+      // subsampling y
+      VP9GetBit(br);
+      // reserved
+      if (VP9GetBit(br)) {
+        LOG(LS_WARNING) << "Failed to get QP. Reserved bit set.";
+        return false;
+      }
+    }
+  } else {
+    if (profile == 1 || profile == 3) {
+      // reserved
+      if (VP9GetBit(br)) {
+        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 = VP9GetValue(br, 16);
+  (void)width;
+  // frame height
+  uint32_t height = VP9GetValue(br, 16);
+  (void)height;
+}
+
+static void VP9ReadRenderSize(VP9BitReader *const br) {
+  // scaling
+  if (VP9GetBit(br)) {
+    // render width
+    uint32_t width = VP9GetValue(br, 16);
+    // render height
+    uint32_t height = VP9GetValue(br, 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 = VP9GetBit(br);
+    if (found_ref)
+      break;
+  }
+
+  if (!found_ref)
+    VP9ReadFrameSize(br);
+
+  VP9ReadRenderSize(br);
+}
+
+static void VP9ReadInterpolationFilter(VP9BitReader *const br) {
+  if (VP9GetBit(br))
+    return;
+
+  VP9GetValue(br, 2);
+}
+
+static void VP9ReadLoopfilter(VP9BitReader *const br) {
+  // filter level
+  VP9GetValue(br, 6);
+  // sharpness level
+  VP9GetValue(br, 3);
+  uint32_t mode_ref_delta_enabled = VP9GetBit(br);
+  if (mode_ref_delta_enabled) {
+    uint32_t mode_ref_delta_update = VP9GetBit(br);
+    if (mode_ref_delta_update) {
+      for (size_t i = 0; i < kVp9MaxRefLFDeltas; i++) {
+        if (VP9GetBit(br))
+          VP9GetSignedValue(br, 6);
+      }
+      for (size_t i = 0; i < kVp9MaxModeLFDeltas; i++) {
+        if (VP9GetBit(br))
+          VP9GetSignedValue(br, 6);
+      }
+    }
+  }
+}
+
+bool GetQp(const uint8_t *buf, size_t length, int *qp) {
+  VP9BitReader br;
+  VP9InitBitReader(&br, buf, buf + length);
+
+  // frame marker
+  if (VP9GetValue(&br, 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 (VP9GetBit(&br)) {
+    VP9GetValue(&br, 3);
+    return false;
+  }
+
+  // frame type: KEY_FRAME(0), INTER_FRAME(1)
+  uint8_t frame_type = VP9GetBit(&br);
+  // show frame
+  uint8_t show_frame = VP9GetBit(&br);
+  // error resilient
+  uint8_t error_resilient = VP9GetBit(&br);
+
+  if (!frame_type) {
+    // sync code
+    uint32_t sync_code = VP9GetValue(&br, 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 = VP9GetBit(&br);
+
+    if (!error_resilient)
+      // reset frame context
+      VP9GetValue(&br, 2);
+
+    if (intra_only) {
+      // sync code
+      if (VP9GetValue(&br, 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
+      VP9GetValue(&br, 8);
+
+      VP9ReadFrameSize(&br);
+      VP9ReadRenderSize(&br);
+    } else {
+      // refresh frame flags
+      int32_t test = VP9GetValue(&br, 8);
+      (void)test;
+
+      for (size_t i = 0; i < kVp9NumRefsPerFrame; i++) {
+        // ref frame index
+        int32_t idx = VP9GetValue(&br, 3);
+        // ref frame sign biases
+        int32_t bias = VP9GetBit(&br);
+        (void)idx;
+        (void)bias;
+      }
+
+      VP9ReadFrameSizeFromRefs(&br);
+
+      // allow high precision mv
+      VP9GetBit(&br);
+
+      // interpolation filter
+      VP9ReadInterpolationFilter(&br);
+    }
+  }
+
+  if (!error_resilient) {
+    // refresh frame context
+    VP9GetBit(&br);
+    // frame parallel decoding mode
+    VP9GetBit(&br);
+  }
+
+  // frame context index
+  VP9GetValue(&br, 2);
+
+  VP9ReadLoopfilter(&br);
+
+  // Base QP.
+  const int base_q0 = VP9GetValue(&br, 8);
+  *qp = base_q0;
+  return true;
+}
+
+}  // namespace vp9
+
+}  // namespace webrtc