Add a Vp9Parser implementation

media/filters/vp9_parser.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// This file contains an implementation of a VP9 bitstream parser.
+
+#include "media/filters/vp9_parser.h"
+
+#include "base/logging.h"
+
+namespace {
+
+int GetMinLog2TileCols(int sb64_cols) {

[Pawel Osciak, 2015/07/30 08:27:37]

static?
Also please document what this function is doing.

[kcwu, 2015/07/31 08:51:51]

IIUC, no need to add static qualifier if it is already in unnamed namespace.

For comments, I don't fully understand these functions and thus only leave
reference to spec.

+  const int kMaxTileWidthB64 = 64;
+  int min_log2 = 0;
+  while ((kMaxTileWidthB64 << min_log2) < sb64_cols)
+    min_log2++;
+  return min_log2;
+}
+
+int GetMaxLog2TileCols(int sb64_cols) {

[Pawel Osciak, 2015/07/30 08:27:37]

static?

[kcwu, 2015/07/31 08:51:51]

Acknowledged.

+  const int kMinTileWidthB64 = 4;
+  int max_log2 = 1;
+  while ((sb64_cols >> max_log2) >= kMinTileWidthB64)
+    max_log2++;
+  return max_log2 - 1;
+}
+
+}  // namespace
+
+namespace media {
+
+Vp9Parser::Vp9Parser() : stream_(nullptr), size_(0) {
+  memset(&ref_slots_, 0, sizeof(ref_slots_));
+}
+
+uint8_t Vp9Parser::ReadProfile() {
+  uint8_t profile = 0;
+
+  // LSB first.
+  profile |= reader_.ReadBit();
+  profile |= reader_.ReadBit() << 1;
+  if (profile > 2)
+    profile |= reader_.ReadBit() << 2;
+  return profile;
+}
+
+bool Vp9Parser::VerifySyncCode() {
+  const int kSyncCode = 0x498342;
+  if (reader_.ReadLiteral(8 * 3) != kSyncCode) {

[Pawel Osciak, 2015/07/30 08:27:37]

General comment: ReadLiteral/ReadBit should have a way to fail, for example if
we are out of data. It should probably return bool and fill argument passed to
it. Please see vp8_parser.cc for example.

[kcwu, 2015/07/31 08:51:51]

Per our chat. We agreed checking reader failure at the end of parsing is not a
bad idea.

+    DLOG(ERROR) << "Invalid frame sync code";
+    return false;

[Pawel Osciak, 2015/07/30 08:27:38]

DVLOG please

[kcwu1, 2015/07/30 08:55:49]

Only this one or all in this class?

[Pawel Osciak, 2015/07/30 08:59:24]

All please.

[kcwu1, 2015/07/31 04:36:01]

Done.

+  }
+  return true;
+}
+
+bool Vp9Parser::ReadBitDepthColorSpaceSampling(Vp9FrameHeader* fhdr) {
+  if (fhdr->profile >= 2) {
+    if (reader_.ReadBit())
+      fhdr->bit_depth = 12;
+    else
+      fhdr->bit_depth = 10;
+  } else {
+    fhdr->bit_depth = 8;
+  }
+
+  fhdr->color_space = static_cast<Vp9ColorSpace>(reader_.ReadLiteral(3));
+  if (fhdr->color_space != Vp9ColorSpace::SRGB) {
+    fhdr->yuv_range = reader_.ReadBit();
+    if (fhdr->profile == 1 || fhdr->profile == 3) {
+      fhdr->subsampling_x = reader_.ReadBit();
+      fhdr->subsampling_y = reader_.ReadBit();
+      if (fhdr->subsampling_x == 1 && fhdr->subsampling_y == 1) {
+        DLOG(ERROR) << "4:2:0 color not supported in profile 1 or 3";
+        return false;
+      }
+      bool reserved = reader_.ReadBit();
+      if (reserved) {
+        DLOG(ERROR) << "reserved bit set";
+        return false;
+      }
+    } else {
+      fhdr->subsampling_x = fhdr->subsampling_y = 1;
+    }
+  } else {
+    if (fhdr->profile == 1 || fhdr->profile == 3) {
+      fhdr->subsampling_x = fhdr->subsampling_y = 0;
+
+      // this bit is not specified in spec??

[Pawel Osciak, 2015/07/30 08:27:37]

s/this/This/
s/??/?/

[kcwu1, 2015/07/30 08:55:49]

just keep note. I expect this will be removed before commit.

+      bool reserved = reader_.ReadBit();
+      if (reserved) {
+        DLOG(ERROR) << "reserved bit set";
+        return false;
+      }
+    } else {
+      DLOG(ERROR) << "4:4:4 color not supported in profile 0 or 2";
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void Vp9Parser::ReadFrameSize(Vp9FrameHeader* fhdr) {
+  fhdr->width = reader_.ReadLiteral(16) + 1;
+  fhdr->height = reader_.ReadLiteral(16) + 1;
+}
+
+void Vp9Parser::ReadFrameSizeFromRefs(Vp9FrameHeader* fhdr) {
+  for (int i = 0; i < kVp9RefsPerFrame; i++) {

[Pawel Osciak, 2015/07/30 08:27:37]

s/int/size_t/

Please use size_t in general for iterating over arrays.

[kcwu1, 2015/07/31 04:36:02]

Done.

+    if (reader_.ReadBit()) {
+      fhdr->width = ref_slots_[i].width;
+      fhdr->height = ref_slots_[i].height;
+      return;
+    }
+  }
+
+  fhdr->width = reader_.ReadLiteral(16) + 1;
+  fhdr->height = reader_.ReadLiteral(16) + 1;
+}
+
+void Vp9Parser::ReadDisplayFrameSize(Vp9FrameHeader* fhdr) {
+  if (reader_.ReadBit()) {
+    fhdr->display_width = reader_.ReadLiteral(16) + 1;
+    fhdr->display_height = reader_.ReadLiteral(16) + 1;
+  } else {
+    fhdr->display_width = fhdr->width;
+    fhdr->display_height = fhdr->height;
+  }
+}
+
+Vp9InterpFilter Vp9Parser::ReadInterpFilter() {
+  if (reader_.ReadBit())
+    return Vp9InterpFilter::INTERP_FILTER_SELECT;
+
+  // The mapping table for next two bits.
+  Vp9InterpFilter table[] = {

[Pawel Osciak, 2015/07/30 08:27:37]

const?

[kcwu1, 2015/07/31 04:36:01]

Done.

+      Vp9InterpFilter::EIGHTTAP_SMOOTH, Vp9InterpFilter::EIGHTTAP,
+      Vp9InterpFilter::EIGHTTAP_SHARP, Vp9InterpFilter::BILINEAR,
+  };
+  return table[reader_.ReadLiteral(2)];

[Pawel Osciak, 2015/07/30 08:27:38]

Is this different from return ReadLiteral(2) + 1 ?

[kcwu1, 2015/07/30 08:55:49]

No difference. I just followed libvpx and feel it reasonable to have a mapping
table.

[Pawel Osciak, 2015/07/30 08:59:24]

Acknowledged.

+}
+
+void Vp9Parser::ReadLoopFilter(Vp9LoopFilter* loop_filter) {
+  loop_filter->filter_level = reader_.ReadLiteral(6);
+  loop_filter->sharpness_level = reader_.ReadLiteral(3);
+
+  loop_filter->mode_ref_delta_enabled = reader_.ReadBit();
+  if (loop_filter->mode_ref_delta_enabled) {
+    loop_filter->mode_ref_delta_update = reader_.ReadBit();
+    if (loop_filter->mode_ref_delta_update) {
+      for (int i = 0; i < Vp9LoopFilter::kNumRefDeltas; i++) {
+        loop_filter->update_ref_deltas[i] = reader_.ReadBit();
+        if (loop_filter->update_ref_deltas[i])
+          loop_filter->ref_deltas[i] = reader_.ReadSignedLiteral(6);
+      }
+
+      for (int i = 0; i < Vp9LoopFilter::kNumModeDeltas; i++) {
+        loop_filter->update_mode_deltas[i] = reader_.ReadBit();
+        if (loop_filter->update_mode_deltas[i])
+          loop_filter->mode_deltas[i] = reader_.ReadLiteral(6);
+      }
+    }
+  } else {
+    loop_filter->mode_ref_delta_update = false;
+  }
+}
+
+void Vp9Parser::ReadQuantization(Vp9QuantizationParams* quants) {
+  quants->base_qindex = reader_.ReadLiteral(8);
+
+  if (reader_.ReadBit())
+    quants->y_dc_delta = reader_.ReadSignedLiteral(4);
+  else
+    quants->y_dc_delta = 0;
+
+  if (reader_.ReadBit())
+    quants->uv_ac_delta = reader_.ReadSignedLiteral(4);
+  else
+    quants->uv_ac_delta = 0;
+
+  if (reader_.ReadBit())
+    quants->uv_dc_delta = reader_.ReadSignedLiteral(4);
+  else
+    quants->uv_dc_delta = 0;
+}
+
+void Vp9Parser::ReadSegmentationMap(Vp9Segmentation* segment) {
+  for (int i = 0; i < Vp9Segmentation::kTreeProbs; i++) {
+    if (reader_.ReadBit())
+      segment->tree_probs[i] = reader_.ReadLiteral(8);
+    else
+      segment->tree_probs[i] = kVp9MaxProb;
+  }
+
+  for (int i = 0; i < Vp9Segmentation::kPredictionProbs; i++)
+    segment->pred_probs[i] = kVp9MaxProb;
+  if (reader_.ReadBit()) {

[Pawel Osciak, 2015/07/30 11:52:31]

Please store this in frame header (as temporal_update).

[kcwu1, 2015/07/31 04:36:01]

Done.

+    for (int i = 0; i < Vp9Segmentation::kPredictionProbs; i++) {
+      if (reader_.ReadBit())
+        segment->pred_probs[i] = reader_.ReadLiteral(8);
+    }
+  }
+}
+
+void Vp9Parser::ReadSegmentationData(Vp9Segmentation* segment) {
+  segment->abs_delta = reader_.ReadBit();
+
+  const int kFeatureDataBits[] = {7, 6, 2, 0};
+  const bool kFeatureDataSigned[] = {true, true, false, false};
+
+  for (int i = 0; i < Vp9Segmentation::kNumSegment; i++) {
+    for (int j = 0; j < Vp9Segmentation::kNumFeature; j++) {
+      int8_t data = 0;
+      segment->feature_enabled[i][j] = reader_.ReadBit();
+      if (segment->feature_enabled[i][j]) {
+        data = reader_.ReadLiteral(kFeatureDataBits[j]);
+        if (kFeatureDataSigned[j])
+          if (reader_.ReadBit())
+            data = -data;
+      }
+      segment->feature_data[i][j] = data;
+    }
+  }
+}
+
+void Vp9Parser::ReadSegmentation(Vp9Segmentation* segment) {
+  segment->enabled = reader_.ReadBit();
+
+  if (!segment->enabled) {
+    segment->update_map = false;
+    segment->update_data = false;
+    return;
+  }
+
+  segment->update_map = reader_.ReadBit();
+  if (segment->update_map)
+    ReadSegmentationMap(segment);
+
+  segment->update_data = reader_.ReadBit();
+  if (segment->update_data)
+    ReadSegmentationData(segment);
+}
+
+void Vp9Parser::ReadTiles(Vp9FrameHeader* fhdr) {
+  int sb64_cols = (fhdr->width + 63) / 64;
+
+  int min_log2_tile_cols = GetMinLog2TileCols(sb64_cols);
+  int max_log2_tile_cols = GetMaxLog2TileCols(sb64_cols);
+
+  int max_ones = max_log2_tile_cols - min_log2_tile_cols;
+  fhdr->log2_tile_cols = min_log2_tile_cols;
+  while (max_ones-- && reader_.ReadBit())
+    fhdr->log2_tile_cols++;
+
+  if (reader_.ReadBit())
+    fhdr->log2_tile_rows = reader_.ReadLiteral(2) - 1;
+  else
+    fhdr->log2_tile_rows = 0;
+}
+
+bool Vp9Parser::ParseUncompressedHeader(Vp9FrameHeader* fhdr) {
+  reader_.Initialize(stream_, size_);
+
+  // frame marker
+  if (reader_.ReadLiteral(2) != 0x2)
+    return false;
+
+  fhdr->profile = ReadProfile();
+  if (fhdr->profile >= kVp9MaxProfile) {
+    DLOG(ERROR) << "Unsupported bitstream profile";
+    return false;
+  }
+
+  fhdr->show_existing_frame = reader_.ReadBit();
+  if (fhdr->show_existing_frame) {
+    fhdr->frame_to_show = reader_.ReadLiteral(3);
+    fhdr->loop_filter.filter_level = 0;

[Pawel Osciak, 2015/07/30 08:27:37]

It seems that sometimes we initialize members to 0 (or false), like here,
sometimes not (segment->update_map/update_data for example). We should make this
consistent, i.e. either depend on the memset to 0, or not (I'd lean towards
depending on zeroing and not 0 or false-initializing).

[kcwu1, 2015/07/31 04:36:01]

Done.

+    fhdr->show_frame = true;
+
+    fhdr->first_partition_size = 0;
+    fhdr->compressed_header = nullptr;
+
+    if (reader_.IsOutOfBuffer()) {

[Pawel Osciak, 2015/07/30 08:27:37]

This shouldn't be needed once we make ReadBit/Literal test.

[kcwu1, 2015/07/30 08:55:49]

Since out of data is rare, I'd prefer checked only once here and not every read.
It makes the code cleaner (and maybe faster). Macros looks ugly and make the
generated code bloat. What do you think?

[Pawel Osciak, 2015/07/30 08:59:24]

We can't read beyond memory that we have available.

[kcwu1, 2015/07/30 09:04:15]

The reader returns 0 if out of buffer. The return value is garbage but guarantee
it's safe.

+      DLOG(ERROR) << "parser reads beyond the end of buffer";
+      return false;
+    }
+    return true;
+  }
+
+  fhdr->frame_type = static_cast<Vp9FrameHeader::FrameType>(reader_.ReadBit());
+  fhdr->show_frame = reader_.ReadBit();
+  fhdr->error_resilient_mode = reader_.ReadBit();
+
+  if (fhdr->IsKeyframe()) {
+    if (!VerifySyncCode())
+      return false;
+
+    if (!ReadBitDepthColorSpaceSampling(fhdr))
+      return false;
+
+    memset(&ref_slots_, 0, sizeof(ref_slots_));
+    for (int i = 0; i < kVp9RefFrames; i++)
+      fhdr->refresh_flag[i] = true;
+
+    ReadFrameSize(fhdr);
+    ReadDisplayFrameSize(fhdr);
+  } else {
+    if (fhdr->show_frame)
+      fhdr->intra_only = false;
+    else
+      fhdr->intra_only = reader_.ReadBit();
+    if (fhdr->error_resilient_mode)

[Pawel Osciak, 2015/07/30 08:27:37]

Please add empty line above.

[kcwu1, 2015/07/31 04:36:01]

Done.

+      fhdr->reset_context = false;
+    else
+      fhdr->reset_context = reader_.ReadLiteral(2);
+
+    if (fhdr->intra_only) {
+      if (!VerifySyncCode())
+        return false;
+
+      if (fhdr->profile > 0) {
+        if (!ReadBitDepthColorSpaceSampling(fhdr))
+          return false;
+      } else {
+        fhdr->bit_depth = 8;
+        fhdr->color_space = Vp9ColorSpace::BT_601;
+        fhdr->subsampling_x = fhdr->subsampling_y = 1;
+      }
+
+      for (int i = 0; i < kVp9RefFrames; i++)
+        fhdr->refresh_flag[i] = reader_.ReadBit();
+      ReadFrameSize(fhdr);
+      ReadDisplayFrameSize(fhdr);
+    } else {
+      for (int i = 0; i < kVp9RefFrames; i++)
+        fhdr->refresh_flag[i] = reader_.ReadBit();
+
+      for (int i = 0; i < kVp9RefsPerFrame; i++) {
+        fhdr->frame_refs[i] = reader_.ReadLiteral(kVp9RefFramesLog2);
+        fhdr->ref_sign_biases[i] = reader_.ReadBit();
+      }
+
+      ReadFrameSizeFromRefs(fhdr);
+      ReadDisplayFrameSize(fhdr);
+
+      fhdr->allow_high_precision_mv = reader_.ReadBit();
+      fhdr->interp_filter = ReadInterpFilter();
+    }
+  }
+
+  if (fhdr->error_resilient_mode) {
+    fhdr->refresh_frame_context = false;
+    fhdr->frame_parallel_decoding_mode = true;
+  } else {
+    fhdr->refresh_frame_context = reader_.ReadBit();
+    fhdr->frame_parallel_decoding_mode = reader_.ReadBit();
+  }
+
+  const int kFrameContextLog2 = 2;

[Pawel Osciak, 2015/07/30 08:27:37]

Any reason to make this specifically into a constant?

[kcwu1, 2015/07/30 08:55:49]

Do you mean why not use literal 2 directly?

[Pawel Osciak, 2015/07/30 08:59:24]

Yes.

[kcwu1, 2015/07/31 04:36:01]

Done.

+  fhdr->frame_context_idx = reader_.ReadLiteral(kFrameContextLog2);
+
+  ReadLoopFilter(&fhdr->loop_filter);
+  ReadQuantization(&fhdr->quant_params);
+  ReadSegmentation(&fhdr->segment);
+
+  ReadTiles(fhdr);
+
+  fhdr->first_partition_size = reader_.ReadLiteral(16);
+  if (fhdr->first_partition_size == 0) {
+    DLOG(ERROR) << "invalid header size";
+    return false;
+  }
+  fhdr->compressed_header = stream_ + reader_.GetBytesRead();

[Pawel Osciak, 2015/07/30 11:52:31]

Could we also store the size of uncompressed header in frame header?

[kcwu1, 2015/07/31 04:36:01]

Done.
And remove |compressed_header| since it is redundant.

+
+  if (reader_.IsOutOfBuffer()) {
+    DLOG(ERROR) << "parser reads beyond the end of buffer";
+    return false;
+  }
+
+  return true;
+}
+
+void Vp9Parser::UpdateSlots(Vp9FrameHeader* fhdr) {
+  for (int i = 0; i < kVp9RefFrames; i++) {
+    if (fhdr->refresh_flag[i]) {
+      ref_slots_[i].used = true;
+      ref_slots_[i].width = fhdr->width;
+      ref_slots_[i].height = fhdr->height;
+    }
+  }
+}
+
+bool Vp9Parser::ParseFrame(const uint8_t* ptr,
+                           size_t frame_size,
+                           Vp9FrameHeader* fhdr) {
+  stream_ = ptr;
+  size_ = frame_size;
+  memset(fhdr, 0, sizeof(*fhdr));
+
+  if (!ParseUncompressedHeader(fhdr))
+    return false;
+
+  UpdateSlots(fhdr);
+
+  return true;
+}
+
+}  // namespace media