webrtc/modules/rtp_rtcp/source/fec_test_helper.cc

/*
 *  Copyright (c) 2012 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/rtp_rtcp/source/fec_test_helper.h"

#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
#include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"

namespace webrtc {

FrameGenerator::FrameGenerator()
    : num_packets_(0), seq_num_(0), timestamp_(0) {}

void FrameGenerator::NewFrame(int num_packets) {
  num_packets_ = num_packets;
  timestamp_ += 3000;
}

uint16_t FrameGenerator::NextSeqNum() { return ++seq_num_; }

test::RawRtpPacket* FrameGenerator::NextPacket(int offset, size_t length) {
  test::RawRtpPacket* rtp_packet = new test::RawRtpPacket;
  for (size_t i = 0; i < length; ++i)
    rtp_packet->data[i + kRtpHeaderSize] = offset + i;
  rtp_packet->length = length + kRtpHeaderSize;
  memset(&rtp_packet->header, 0, sizeof(WebRtcRTPHeader));
  rtp_packet->header.frameType = kVideoFrameDelta;
  rtp_packet->header.header.headerLength = kRtpHeaderSize;
  rtp_packet->header.header.markerBit = (num_packets_ == 1);
  rtp_packet->header.header.sequenceNumber = seq_num_;
  rtp_packet->header.header.timestamp = timestamp_;
  rtp_packet->header.header.payloadType = kVp8PayloadType;
  BuildRtpHeader(rtp_packet->data, &rtp_packet->header.header);
  ++seq_num_;
  --num_packets_;
  return rtp_packet;
}

// Creates a new RtpPacket with the RED header added to the packet.
test::RawRtpPacket* FrameGenerator::BuildMediaRedPacket(
    const test::RawRtpPacket* packet) {
  const size_t kHeaderLength = packet->header.header.headerLength;
  test::RawRtpPacket* red_packet = new test::RawRtpPacket;
  red_packet->header = packet->header;
  red_packet->length = packet->length + 1;  // 1 byte RED header.
  memset(red_packet->data, 0, red_packet->length);
  // Copy RTP header.
  memcpy(red_packet->data, packet->data, kHeaderLength);
  SetRedHeader(red_packet, red_packet->data[1] & 0x7f, kHeaderLength);
  memcpy(red_packet->data + kHeaderLength + 1, packet->data + kHeaderLength,
         packet->length - kHeaderLength);
  return red_packet;
}

// Creates a new RtpPacket with FEC payload and red header. Does this by
// creating a new fake media RtpPacket, clears the marker bit and adds a RED
// header. Finally replaces the payload with the content of |packet->data|.
test::RawRtpPacket* FrameGenerator::BuildFecRedPacket(
    const ForwardErrorCorrection::Packet* packet) {
  // Create a fake media packet to get a correct header. 1 byte RED header.
  ++num_packets_;
  test::RawRtpPacket* red_packet = NextPacket(0, packet->length + 1);
  red_packet->data[1] &= ~0x80;  // Clear marker bit.
  const size_t kHeaderLength = red_packet->header.header.headerLength;
  SetRedHeader(red_packet, kFecPayloadType, kHeaderLength);
  memcpy(red_packet->data + kHeaderLength + 1, packet->data, packet->length);
  red_packet->length = kHeaderLength + 1 + packet->length;
  return red_packet;
}

void FrameGenerator::SetRedHeader(ForwardErrorCorrection::Packet* red_packet,
                                  uint8_t payload_type,
                                  size_t header_length) const {
  // Replace pltype.
  red_packet->data[1] &= 0x80;             // Reset.
  red_packet->data[1] += kRedPayloadType;  // Replace.

  // Add RED header, f-bit always 0.
  red_packet->data[header_length] = payload_type;
}

void FrameGenerator::BuildRtpHeader(uint8_t* data, const RTPHeader* header) {
  data[0] = 0x80;  // Version 2.
  data[1] = header->payloadType;
  data[1] |= (header->markerBit ? kRtpMarkerBitMask : 0);
  ByteWriter<uint16_t>::WriteBigEndian(data + 2, header->sequenceNumber);
  ByteWriter<uint32_t>::WriteBigEndian(data + 4, header->timestamp);
  ByteWriter<uint32_t>::WriteBigEndian(data + 8, header->ssrc);
}

}  // namespace webrtc