Build AVC decoder configuration record

content/common/gpu/media/avc_config_record_builder.cc

+// Copyright (c) 2012 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.
+
+#include "content/common/gpu/media/avc_config_record_builder.h"
+
+#include "base/logging.h"
+#include "content/common/gpu/media/h264_parser.h"
+
+namespace content {
+
+AVCConfigRecordBuilder::AVCConfigRecordBuilder()
+    : sps_profile_idc_(0),
+      sps_constraint_setx_flag_(0),
+      sps_level_idc_(0),
+      coded_width_(0),
+      coded_height_(0) {
+}
+
+AVCConfigRecordBuilder::~AVCConfigRecordBuilder() {
+}
+
+bool AVCConfigRecordBuilder::ProcessNALU(
+    H264Parser* parser,
+    const H264NALU& nalu,
+    std::vector<uint8_t>* config_record) {
+  if (nalu.nal_unit_type == H264NALU::kSPS) {
+    return ProcessSPS(parser, nalu);
+  } else if (nalu.nal_unit_type == H264NALU::kPPS) {
+    return ProcessPPS(parser, nalu);
+  } else if (nalu.nal_unit_type >= 1 && nalu.nal_unit_type <= 5) {
+    // Ready to build the AVC decoder configuration record once the first slice
+    // type is encountered.
+    *config_record = BuildConfigRecord();
+    return true;
+  }
+  // Skip this NALU.

[Ami GONE FROM CHROMIUM, 2012/05/30 00:07:54]

Comment is outdated?

(what is the correct thing to do if we see a non-SPS/PPS/slice NALU?)

[sail, 2012/06/02 21:05:49]

Returning true effectively skips the NALU. Updated the commented to make this
more clear.
The builder must skip these NALUs otherwise it won't be able to build a config
record. For example, the steam in test-25fps.h264 starts with a SEI Message
type.

+  return true;
+}
+
+std::vector<uint8_t> AVCConfigRecordBuilder::BuildConfigRecord() {
+  // 5 bytes for AVC record header. 1 byte for the number of SPS units.
+  // 1 byte for the number of PPS units.
+  int record_size = 7;
+  for (NALUVector::const_iterator it = sps_nalus_.begin();
+       it != sps_nalus_.end(); ++it) {
+    // Plus 2 bytes to store the SPS size.
+    record_size += (*it)->size() + 2;
+  }
+  for (NALUVector::const_iterator it = pps_nalus_.begin();
+       it != pps_nalus_.end(); ++it) {
+    // Plus 2 bytes to store the PPS size.
+    record_size += (*it)->size() + 2;
+  }
+  std::vector<uint8_t> extra_data(record_size);
+
+  // AVC decoder configuration record version.
+  extra_data[0] = 0x01;
+  // Profile.
+  extra_data[1] = sps_profile_idc_ & 0xff;
+  // Profile compatibility, must match the byte between profile IDC
+  // and level IDC in the SPS.
+  extra_data[2] = sps_constraint_setx_flag_;
+  // AVC level.
+  extra_data[3] = sps_level_idc_ & 0xff;
+
+  // TODO(sail): There's no way to get the NALU length field size from the
+  // SPS and PPS data. Just assume 4 for now.
+  const int kNALULengthFieldSize = 4;
+
+  // The first 6 bits are reserved and must be 1. Last two bits are the
+  // NALU field size minus 1.
+  extra_data[4] = 0xfc | ((kNALULengthFieldSize - 1) & 0x03);
+
+  // The first 3 bits are reserved and must be 1. Last 5 bits are the
+  // number of SPS units.
+  extra_data[5] = 0xe0 | (sps_nalus_.size() & 0x1f);
+  int index = 6;
+  if (!sps_nalus_.empty())

[Ami GONE FROM CHROMIUM, 2012/05/30 00:07:54]

CNTCR() is safe to call w/ an empty vector, so this conditional is unnecessary?

(ditto for PPS below)

[sail, 2012/06/02 21:05:49]

Done.

+    index += CopyNALUsToConfigRecord(sps_nalus_, &extra_data[index]);
+
+  // The number of PPS units.
+  extra_data[index++] = pps_nalus_.size() & 0xff;
+  if (!pps_nalus_.empty())
+    CopyNALUsToConfigRecord(pps_nalus_, &extra_data[index]);
+
+  return extra_data;
+}
+
+int AVCConfigRecordBuilder::CopyNALUsToConfigRecord(const NALUVector& nalus,
+                                                    uint8_t* record_buffer) {
+  int index = 0;
+  for (NALUVector::const_iterator it = nalus.begin();
+       it != nalus.end(); ++it) {
+    // High byte of the SPS unit size.

[Ami GONE FROM CHROMIUM, 2012/05/30 00:07:54]

drop SPS here and below.

[sail, 2012/06/02 21:05:49]

Done.

+    record_buffer[index++] = ((*it)->size() >> 8) & 0xff;
+    // Low byte of the SPS unit size.
+    record_buffer[index++] = (*it)->size() & 0xff;
+    // The SPS data.
+    memcpy(record_buffer + index, (*it)->front(), (*it)->size());
+    index += (*it)->size();
+  }
+  return index;
+}
+
+bool AVCConfigRecordBuilder::ProcessSPS(H264Parser* parser,
+                                        const H264NALU& nalu) {
+  int sps_id = 0;
+  H264Parser::Result result = parser->ParseSPS(&sps_id);
+  if (result != H264Parser::kOk)
+    return false;
+
+  std::vector<uint8_t> bytes(nalu.data, nalu.data + nalu.size);
+  sps_nalus_.push_back(base::RefCountedBytes::TakeVector(&bytes));
+
+  const H264SPS* sps = parser->GetSPS(sps_id);
+
+  // Use the last width and height that are encountered.
+  coded_width_ = (sps->pic_width_in_mbs_minus1 + 1) * 16;
+  if (sps->frame_mbs_only_flag)
+    coded_height_ = (sps->pic_height_in_map_units_minus1 + 1) * 16;
+  else
+    coded_height_ = (sps->pic_height_in_map_units_minus1 + 1) * 32;
+
+  // Use the last video profile and flags that are encountered.
+  sps_profile_idc_ = sps->profile_idc;
+  sps_constraint_setx_flag_ = sps->constraint_setx_flag;
+  // Use the largest AVC level that's encountered.
+  sps_level_idc_ = std::max(sps_level_idc_, sps->level_idc);
+
+  return true;
+}
+
+bool AVCConfigRecordBuilder::ProcessPPS(H264Parser* parser,
+                                        const H264NALU& nalu) {
+  int pps_id = 0;
+  H264Parser::Result result = parser->ParsePPS(&pps_id);
+  if (result != H264Parser::kOk)
+    return false;
+
+  std::vector<uint8_t> bytes(nalu.data, nalu.data + nalu.size);
+  pps_nalus_.push_back(base::RefCountedBytes::TakeVector(&bytes));
+  return true;
+}
+
+}  // namespace content