modules/rtp_rtcp/source/rtp_header_extensions.cc - src/webrtc - Git at Google

 /*
  *  Copyright (c) 2016 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/rtp_header_extensions.h"

 #include "webrtc/modules/rtp_rtcp/include/rtp_cvo.h"
 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/logging.h"

 namespace webrtc {
 // Absolute send time in RTP streams.
 //
 // The absolute send time is signaled to the receiver in-band using the
 // general mechanism for RTP header extensions [RFC5285]. The payload
 // of this extension (the transmitted value) is a 24-bit unsigned integer
 // containing the sender's current time in seconds as a fixed point number
 // with 18 bits fractional part.
 //
 // The form of the absolute send time extension block:
 //
 //    0                   1                   2                   3
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=2 |              absolute send time               |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType AbsoluteSendTime::kId;
 constexpr uint8_t AbsoluteSendTime::kValueSizeBytes;
 constexpr const char AbsoluteSendTime::kUri[];

 bool AbsoluteSendTime::Parse(rtc::ArrayView<const uint8_t> data,
                              uint32_t* time_24bits) {
   if (data.size() != 3)
     return false;
   *time_24bits = ByteReader<uint32_t, 3>::ReadBigEndian(data.data());
   return true;
 }

 bool AbsoluteSendTime::Write(uint8_t* data, uint32_t time_24bits) {
   RTC_DCHECK_LE(time_24bits, 0x00FFFFFF);
   ByteWriter<uint32_t, 3>::WriteBigEndian(data, time_24bits);
   return true;
 }

 // An RTP Header Extension for Client-to-Mixer Audio Level Indication
 //
 // https://datatracker.ietf.org/doc/draft-lennox-avt-rtp-audio-level-exthdr/
 //
 // The form of the audio level extension block:
 //
 //    0                   1
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=0 |V|   level     |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //
 constexpr RTPExtensionType AudioLevel::kId;
 constexpr uint8_t AudioLevel::kValueSizeBytes;
 constexpr const char AudioLevel::kUri[];

 bool AudioLevel::Parse(rtc::ArrayView<const uint8_t> data,
                        bool* voice_activity,
                        uint8_t* audio_level) {
   if (data.size() != 1)
     return false;
   *voice_activity = (data[0] & 0x80) != 0;
   *audio_level = data[0] & 0x7F;
   return true;
 }

 bool AudioLevel::Write(uint8_t* data,
                        bool voice_activity,
                        uint8_t audio_level) {
   RTC_CHECK_LE(audio_level, 0x7f);
   data[0] = (voice_activity ? 0x80 : 0x00) | audio_level;
   return true;
 }

 // From RFC 5450: Transmission Time Offsets in RTP Streams.
 //
 // The transmission time is signaled to the receiver in-band using the
 // general mechanism for RTP header extensions [RFC5285]. The payload
 // of this extension (the transmitted value) is a 24-bit signed integer.
 // When added to the RTP timestamp of the packet, it represents the
 // "effective" RTP transmission time of the packet, on the RTP
 // timescale.
 //
 // The form of the transmission offset extension block:
 //
 //    0                   1                   2                   3
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=2 |              transmission offset              |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType TransmissionOffset::kId;
 constexpr uint8_t TransmissionOffset::kValueSizeBytes;
 constexpr const char TransmissionOffset::kUri[];

 bool TransmissionOffset::Parse(rtc::ArrayView<const uint8_t> data,
                                int32_t* rtp_time) {
   if (data.size() != 3)
     return false;
   *rtp_time = ByteReader<int32_t, 3>::ReadBigEndian(data.data());
   return true;
 }

 bool TransmissionOffset::Write(uint8_t* data, int32_t rtp_time) {
   RTC_DCHECK_LE(rtp_time, 0x00ffffff);
   ByteWriter<int32_t, 3>::WriteBigEndian(data, rtp_time);
   return true;
 }

 //   0                   1                   2
 //   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  |  ID   | L=1   |transport wide sequence number |
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType TransportSequenceNumber::kId;
 constexpr uint8_t TransportSequenceNumber::kValueSizeBytes;
 constexpr const char TransportSequenceNumber::kUri[];

 bool TransportSequenceNumber::Parse(rtc::ArrayView<const uint8_t> data,
                                     uint16_t* value) {
   if (data.size() != 2)
     return false;
   *value = ByteReader<uint16_t>::ReadBigEndian(data.data());
   return true;
 }

 bool TransportSequenceNumber::Write(uint8_t* data, uint16_t value) {
   ByteWriter<uint16_t>::WriteBigEndian(data, value);
   return true;
 }

 // Coordination of Video Orientation in RTP streams.
 //
 // Coordination of Video Orientation consists in signaling of the current
 // orientation of the image captured on the sender side to the receiver for
 // appropriate rendering and displaying.
 //
 //    0                   1
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=0 |0 0 0 0 C F R R|
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType VideoOrientation::kId;
 constexpr uint8_t VideoOrientation::kValueSizeBytes;
 constexpr const char VideoOrientation::kUri[];

 bool VideoOrientation::Parse(rtc::ArrayView<const uint8_t> data,
                              VideoRotation* rotation) {
   if (data.size() != 1)
     return false;
   *rotation = ConvertCVOByteToVideoRotation(data[0]);
   return true;
 }

 bool VideoOrientation::Write(uint8_t* data, VideoRotation rotation) {
   data[0] = ConvertVideoRotationToCVOByte(rotation);
   return true;
 }

 bool VideoOrientation::Parse(rtc::ArrayView<const uint8_t> data,
                              uint8_t* value) {
   if (data.size() != 1)
     return false;
   *value = data[0];
   return true;
 }

 bool VideoOrientation::Write(uint8_t* data, uint8_t value) {
   data[0] = value;
   return true;
 }

 //   0                   1                   2                   3
 //   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  |  ID   | len=2 |   MIN delay           |   MAX delay           |
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType PlayoutDelayLimits::kId;
 constexpr uint8_t PlayoutDelayLimits::kValueSizeBytes;
 constexpr const char PlayoutDelayLimits::kUri[];

 bool PlayoutDelayLimits::Parse(rtc::ArrayView<const uint8_t> data,
                                PlayoutDelay* playout_delay) {
   RTC_DCHECK(playout_delay);
   if (data.size() != 3)
     return false;
   uint32_t raw = ByteReader<uint32_t, 3>::ReadBigEndian(data.data());
   uint16_t min_raw = (raw >> 12);
   uint16_t max_raw = (raw & 0xfff);
   if (min_raw > max_raw)
     return false;
   playout_delay->min_ms = min_raw * kGranularityMs;
   playout_delay->max_ms = max_raw * kGranularityMs;
   return true;
 }

 bool PlayoutDelayLimits::Write(uint8_t* data,
                                const PlayoutDelay& playout_delay) {
   RTC_DCHECK_LE(0, playout_delay.min_ms);
   RTC_DCHECK_LE(playout_delay.min_ms, playout_delay.max_ms);
   RTC_DCHECK_LE(playout_delay.max_ms, kMaxMs);
   // Convert MS to value to be sent on extension header.
   uint32_t min_delay = playout_delay.min_ms / kGranularityMs;
   uint32_t max_delay = playout_delay.max_ms / kGranularityMs;
   ByteWriter<uint32_t, 3>::WriteBigEndian(data, (min_delay << 12) | max_delay);
   return true;
 }

 // Video Content Type.
 //
 // E.g. default video or screenshare.
 //
 //    0                   1
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=0 | Content type  |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType VideoContentTypeExtension::kId;
 constexpr uint8_t VideoContentTypeExtension::kValueSizeBytes;
 constexpr const char VideoContentTypeExtension::kUri[];

 bool VideoContentTypeExtension::Parse(rtc::ArrayView<const uint8_t> data,
                                       VideoContentType* content_type) {
   if (data.size() == 1 &&
       data[0] < static_cast<uint8_t>(VideoContentType::TOTAL_CONTENT_TYPES)) {
     *content_type = static_cast<VideoContentType>(data[0]);
     return true;
   }
   return false;
 }

 bool VideoContentTypeExtension::Write(uint8_t* data,
                                       VideoContentType content_type) {
   data[0] = static_cast<uint8_t>(content_type);
   return true;
 }

 // Video Timing.
 // 6 timestamps in milliseconds counted from capture time stored in rtp header:
 // encode start/finish, packetization complete, pacer exit and reserved for
 // modification by the network modification. |flags| is a bitmask and has the
 // following allowed values:
 // 0 = Valid data, but no flags available (backwards compatibility)
 // 1 = Frame marked as timing frame due to cyclic timer.
 // 2 = Frame marked as timing frame due to size being outside limit.
 // 255 = Invalid. The whole timing frame extension should be ignored.
 //
 //    0                   1                   2                   3
 //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=12|     flags     |     encode start ms delta       |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |    encode finish ms delta     |   packetizer finish ms delta    |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |     pacer exit ms delta       |   network timestamp ms delta    |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  network2 timestamp ms delta  |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 constexpr RTPExtensionType VideoTimingExtension::kId;
 constexpr uint8_t VideoTimingExtension::kValueSizeBytes;
 constexpr const char VideoTimingExtension::kUri[];

 bool VideoTimingExtension::Parse(rtc::ArrayView<const uint8_t> data,
                                  VideoSendTiming* timing) {
   RTC_DCHECK(timing);
   // TODO(sprang): Deprecate support for old wire format.
   ptrdiff_t off = 0;
   switch (data.size()) {
     case kValueSizeBytes - 1:
       timing->flags = 0;
       off = 1;  // Old wire format without the flags field.
       break;
     case kValueSizeBytes:
       timing->flags = ByteReader<uint8_t>::ReadBigEndian(data.data());
       break;
     default:
       return false;
   }

   timing->encode_start_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kEncodeStartDeltaOffset - off);
   timing->encode_finish_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kEncodeFinishDeltaOffset - off);
   timing->packetization_finish_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kPacketizationFinishDeltaOffset - off);
   timing->pacer_exit_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kPacerExitDeltaOffset - off);
   timing->network_timstamp_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kNetworkTimestampDeltaOffset - off);
   timing->network2_timstamp_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
       data.data() + VideoSendTiming::kNetwork2TimestampDeltaOffset - off);
   return true;
 }

 bool VideoTimingExtension::Write(uint8_t* data, const VideoSendTiming& timing) {
   ByteWriter<uint8_t>::WriteBigEndian(data + VideoSendTiming::kFlagsOffset,
                                       timing.flags);
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kEncodeStartDeltaOffset,
       timing.encode_start_delta_ms);
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kEncodeFinishDeltaOffset,
       timing.encode_finish_delta_ms);
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kPacketizationFinishDeltaOffset,
       timing.packetization_finish_delta_ms);
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kPacerExitDeltaOffset,
       timing.pacer_exit_delta_ms);
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kNetworkTimestampDeltaOffset, 0);  // reserved
   ByteWriter<uint16_t>::WriteBigEndian(
       data + VideoSendTiming::kNetwork2TimestampDeltaOffset, 0);  // reserved
   return true;
 }

 bool VideoTimingExtension::Write(uint8_t* data,
                                  uint16_t time_delta_ms,
                                  uint8_t offset) {
   RTC_DCHECK_LT(offset, kValueSizeBytes - sizeof(uint16_t));
   ByteWriter<uint16_t>::WriteBigEndian(data + offset, time_delta_ms);
   return true;
 }

 bool BaseRtpStringExtension::Parse(rtc::ArrayView<const uint8_t> data,
                                    StringRtpHeaderExtension* str) {
   if (data.empty() || data[0] == 0)  // Valid string extension can't be empty.
     return false;
   str->Set(data);
   RTC_DCHECK(!str->empty());
   return true;
 }

 bool BaseRtpStringExtension::Write(uint8_t* data,
                                    const StringRtpHeaderExtension& str) {
   RTC_DCHECK_GE(str.size(), 1);
   RTC_DCHECK_LE(str.size(), StringRtpHeaderExtension::kMaxSize);
   memcpy(data, str.data(), str.size());
   return true;
 }

 bool BaseRtpStringExtension::Parse(rtc::ArrayView<const uint8_t> data,
                                    std::string* str) {
   if (data.empty() || data[0] == 0)  // Valid string extension can't be empty.
     return false;
   const char* cstr = reinterpret_cast<const char*>(data.data());
   // If there is a \0 character in the middle of the |data|, treat it as end
   // of the string. Well-formed string extensions shouldn't contain it.
   str->assign(cstr, strnlen(cstr, data.size()));
   RTC_DCHECK(!str->empty());
   return true;
 }

 bool BaseRtpStringExtension::Write(uint8_t* data, const std::string& str) {
   RTC_DCHECK_GE(str.size(), 1);
   RTC_DCHECK_LE(str.size(), StringRtpHeaderExtension::kMaxSize);
   memcpy(data, str.data(), str.size());
   return true;
 }

 // Constant declarations for string RTP header extension types.

 constexpr RTPExtensionType RtpStreamId::kId;
 constexpr const char RtpStreamId::kUri[];

 constexpr RTPExtensionType RepairedRtpStreamId::kId;
 constexpr const char RepairedRtpStreamId::kUri[];

 constexpr RTPExtensionType RtpMid::kId;
 constexpr const char RtpMid::kUri[];

 }  // namespace webrtc
	/*
	* Copyright (c) 2016 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/rtp_header_extensions.h"

	#include "webrtc/modules/rtp_rtcp/include/rtp_cvo.h"
	#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
	#include "webrtc/rtc_base/checks.h"
	#include "webrtc/rtc_base/logging.h"

	namespace webrtc {
	// Absolute send time in RTP streams.
	//
	// The absolute send time is signaled to the receiver in-band using the
	// general mechanism for RTP header extensions [RFC5285]. The payload
	// of this extension (the transmitted value) is a 24-bit unsigned integer
	// containing the sender's current time in seconds as a fixed point number
	// with 18 bits fractional part.
	//
	// The form of the absolute send time extension block:
	//
	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=2 \| absolute send time \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType AbsoluteSendTime::kId;
	constexpr uint8_t AbsoluteSendTime::kValueSizeBytes;
	constexpr const char AbsoluteSendTime::kUri[];

	bool AbsoluteSendTime::Parse(rtc::ArrayView<const uint8_t> data,
	uint32_t* time_24bits) {
	if (data.size() != 3)
	return false;
	*time_24bits = ByteReader<uint32_t, 3>::ReadBigEndian(data.data());
	return true;
	}

	bool AbsoluteSendTime::Write(uint8_t* data, uint32_t time_24bits) {
	RTC_DCHECK_LE(time_24bits, 0x00FFFFFF);
	ByteWriter<uint32_t, 3>::WriteBigEndian(data, time_24bits);
	return true;
	}

	// An RTP Header Extension for Client-to-Mixer Audio Level Indication
	//
	// https://datatracker.ietf.org/doc/draft-lennox-avt-rtp-audio-level-exthdr/
	//
	// The form of the audio level extension block:
	//
	// 0 1
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=0 \|V\| level \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	//
	constexpr RTPExtensionType AudioLevel::kId;
	constexpr uint8_t AudioLevel::kValueSizeBytes;
	constexpr const char AudioLevel::kUri[];

	bool AudioLevel::Parse(rtc::ArrayView<const uint8_t> data,
	bool* voice_activity,
	uint8_t* audio_level) {
	if (data.size() != 1)
	return false;
	*voice_activity = (data[0] & 0x80) != 0;
	*audio_level = data[0] & 0x7F;
	return true;
	}

	bool AudioLevel::Write(uint8_t* data,
	bool voice_activity,
	uint8_t audio_level) {
	RTC_CHECK_LE(audio_level, 0x7f);
	data[0] = (voice_activity ? 0x80 : 0x00) \| audio_level;
	return true;
	}

	// From RFC 5450: Transmission Time Offsets in RTP Streams.
	//
	// The transmission time is signaled to the receiver in-band using the
	// general mechanism for RTP header extensions [RFC5285]. The payload
	// of this extension (the transmitted value) is a 24-bit signed integer.
	// When added to the RTP timestamp of the packet, it represents the
	// "effective" RTP transmission time of the packet, on the RTP
	// timescale.
	//
	// The form of the transmission offset extension block:
	//
	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=2 \| transmission offset \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType TransmissionOffset::kId;
	constexpr uint8_t TransmissionOffset::kValueSizeBytes;
	constexpr const char TransmissionOffset::kUri[];

	bool TransmissionOffset::Parse(rtc::ArrayView<const uint8_t> data,
	int32_t* rtp_time) {
	if (data.size() != 3)
	return false;
	*rtp_time = ByteReader<int32_t, 3>::ReadBigEndian(data.data());
	return true;
	}

	bool TransmissionOffset::Write(uint8_t* data, int32_t rtp_time) {
	RTC_DCHECK_LE(rtp_time, 0x00ffffff);
	ByteWriter<int32_t, 3>::WriteBigEndian(data, rtp_time);
	return true;
	}

	// 0 1 2
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| L=1 \|transport wide sequence number \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType TransportSequenceNumber::kId;
	constexpr uint8_t TransportSequenceNumber::kValueSizeBytes;
	constexpr const char TransportSequenceNumber::kUri[];

	bool TransportSequenceNumber::Parse(rtc::ArrayView<const uint8_t> data,
	uint16_t* value) {
	if (data.size() != 2)
	return false;
	*value = ByteReader<uint16_t>::ReadBigEndian(data.data());
	return true;
	}

	bool TransportSequenceNumber::Write(uint8_t* data, uint16_t value) {
	ByteWriter<uint16_t>::WriteBigEndian(data, value);
	return true;
	}

	// Coordination of Video Orientation in RTP streams.
	//
	// Coordination of Video Orientation consists in signaling of the current
	// orientation of the image captured on the sender side to the receiver for
	// appropriate rendering and displaying.
	//
	// 0 1
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=0 \|0 0 0 0 C F R R\|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType VideoOrientation::kId;
	constexpr uint8_t VideoOrientation::kValueSizeBytes;
	constexpr const char VideoOrientation::kUri[];

	bool VideoOrientation::Parse(rtc::ArrayView<const uint8_t> data,
	VideoRotation* rotation) {
	if (data.size() != 1)
	return false;
	*rotation = ConvertCVOByteToVideoRotation(data[0]);
	return true;
	}

	bool VideoOrientation::Write(uint8_t* data, VideoRotation rotation) {
	data[0] = ConvertVideoRotationToCVOByte(rotation);
	return true;
	}

	bool VideoOrientation::Parse(rtc::ArrayView<const uint8_t> data,
	uint8_t* value) {
	if (data.size() != 1)
	return false;
	*value = data[0];
	return true;
	}

	bool VideoOrientation::Write(uint8_t* data, uint8_t value) {
	data[0] = value;
	return true;
	}

	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=2 \| MIN delay \| MAX delay \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType PlayoutDelayLimits::kId;
	constexpr uint8_t PlayoutDelayLimits::kValueSizeBytes;
	constexpr const char PlayoutDelayLimits::kUri[];

	bool PlayoutDelayLimits::Parse(rtc::ArrayView<const uint8_t> data,
	PlayoutDelay* playout_delay) {
	RTC_DCHECK(playout_delay);
	if (data.size() != 3)
	return false;
	uint32_t raw = ByteReader<uint32_t, 3>::ReadBigEndian(data.data());
	uint16_t min_raw = (raw >> 12);
	uint16_t max_raw = (raw & 0xfff);
	if (min_raw > max_raw)
	return false;
	playout_delay->min_ms = min_raw * kGranularityMs;
	playout_delay->max_ms = max_raw * kGranularityMs;
	return true;
	}

	bool PlayoutDelayLimits::Write(uint8_t* data,
	const PlayoutDelay& playout_delay) {
	RTC_DCHECK_LE(0, playout_delay.min_ms);
	RTC_DCHECK_LE(playout_delay.min_ms, playout_delay.max_ms);
	RTC_DCHECK_LE(playout_delay.max_ms, kMaxMs);
	// Convert MS to value to be sent on extension header.
	uint32_t min_delay = playout_delay.min_ms / kGranularityMs;
	uint32_t max_delay = playout_delay.max_ms / kGranularityMs;
	ByteWriter<uint32_t, 3>::WriteBigEndian(data, (min_delay << 12) \| max_delay);
	return true;
	}

	// Video Content Type.
	//
	// E.g. default video or screenshare.
	//
	// 0 1
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=0 \| Content type \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	constexpr RTPExtensionType VideoContentTypeExtension::kId;
	constexpr uint8_t VideoContentTypeExtension::kValueSizeBytes;
	constexpr const char VideoContentTypeExtension::kUri[];

	bool VideoContentTypeExtension::Parse(rtc::ArrayView<const uint8_t> data,
	VideoContentType* content_type) {
	if (data.size() == 1 &&
	data[0] < static_cast<uint8_t>(VideoContentType::TOTAL_CONTENT_TYPES)) {
	*content_type = static_cast<VideoContentType>(data[0]);
	return true;
	}
	return false;
	}

	bool VideoContentTypeExtension::Write(uint8_t* data,
	VideoContentType content_type) {
	data[0] = static_cast<uint8_t>(content_type);
	return true;
	}

	// Video Timing.
	// 6 timestamps in milliseconds counted from capture time stored in rtp header:
	// encode start/finish, packetization complete, pacer exit and reserved for
	// modification by the network modification. \|flags\| is a bitmask and has the
	// following allowed values:
	// 0 = Valid data, but no flags available (backwards compatibility)
	// 1 = Frame marked as timing frame due to cyclic timer.
	// 2 = Frame marked as timing frame due to size being outside limit.
	// 255 = Invalid. The whole timing frame extension should be ignored.
	//
	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| ID \| len=12\| flags \| encode start ms delta \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| encode finish ms delta \| packetizer finish ms delta \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| pacer exit ms delta \| network timestamp ms delta \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \| network2 timestamp ms delta \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	constexpr RTPExtensionType VideoTimingExtension::kId;
	constexpr uint8_t VideoTimingExtension::kValueSizeBytes;
	constexpr const char VideoTimingExtension::kUri[];

	bool VideoTimingExtension::Parse(rtc::ArrayView<const uint8_t> data,
	VideoSendTiming* timing) {
	RTC_DCHECK(timing);
	// TODO(sprang): Deprecate support for old wire format.
	ptrdiff_t off = 0;
	switch (data.size()) {
	case kValueSizeBytes - 1:
	timing->flags = 0;
	off = 1; // Old wire format without the flags field.
	break;
	case kValueSizeBytes:
	timing->flags = ByteReader<uint8_t>::ReadBigEndian(data.data());
	break;
	default:
	return false;
	}

	timing->encode_start_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kEncodeStartDeltaOffset - off);
	timing->encode_finish_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kEncodeFinishDeltaOffset - off);
	timing->packetization_finish_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kPacketizationFinishDeltaOffset - off);
	timing->pacer_exit_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kPacerExitDeltaOffset - off);
	timing->network_timstamp_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kNetworkTimestampDeltaOffset - off);
	timing->network2_timstamp_delta_ms = ByteReader<uint16_t>::ReadBigEndian(
	data.data() + VideoSendTiming::kNetwork2TimestampDeltaOffset - off);
	return true;
	}

	bool VideoTimingExtension::Write(uint8_t* data, const VideoSendTiming& timing) {
	ByteWriter<uint8_t>::WriteBigEndian(data + VideoSendTiming::kFlagsOffset,
	timing.flags);
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kEncodeStartDeltaOffset,
	timing.encode_start_delta_ms);
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kEncodeFinishDeltaOffset,
	timing.encode_finish_delta_ms);
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kPacketizationFinishDeltaOffset,
	timing.packetization_finish_delta_ms);
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kPacerExitDeltaOffset,
	timing.pacer_exit_delta_ms);
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kNetworkTimestampDeltaOffset, 0); // reserved
	ByteWriter<uint16_t>::WriteBigEndian(
	data + VideoSendTiming::kNetwork2TimestampDeltaOffset, 0); // reserved
	return true;
	}

	bool VideoTimingExtension::Write(uint8_t* data,
	uint16_t time_delta_ms,
	uint8_t offset) {
	RTC_DCHECK_LT(offset, kValueSizeBytes - sizeof(uint16_t));
	ByteWriter<uint16_t>::WriteBigEndian(data + offset, time_delta_ms);
	return true;
	}

	bool BaseRtpStringExtension::Parse(rtc::ArrayView<const uint8_t> data,
	StringRtpHeaderExtension* str) {
	if (data.empty() \|\| data[0] == 0) // Valid string extension can't be empty.
	return false;
	str->Set(data);
	RTC_DCHECK(!str->empty());
	return true;
	}

	bool BaseRtpStringExtension::Write(uint8_t* data,
	const StringRtpHeaderExtension& str) {
	RTC_DCHECK_GE(str.size(), 1);
	RTC_DCHECK_LE(str.size(), StringRtpHeaderExtension::kMaxSize);
	memcpy(data, str.data(), str.size());
	return true;
	}

	bool BaseRtpStringExtension::Parse(rtc::ArrayView<const uint8_t> data,
	std::string* str) {
	if (data.empty() \|\| data[0] == 0) // Valid string extension can't be empty.
	return false;
	const char* cstr = reinterpret_cast<const char*>(data.data());
	// If there is a \0 character in the middle of the \|data\|, treat it as end
	// of the string. Well-formed string extensions shouldn't contain it.
	str->assign(cstr, strnlen(cstr, data.size()));
	RTC_DCHECK(!str->empty());
	return true;
	}

	bool BaseRtpStringExtension::Write(uint8_t* data, const std::string& str) {
	RTC_DCHECK_GE(str.size(), 1);
	RTC_DCHECK_LE(str.size(), StringRtpHeaderExtension::kMaxSize);
	memcpy(data, str.data(), str.size());
	return true;
	}

	// Constant declarations for string RTP header extension types.

	constexpr RTPExtensionType RtpStreamId::kId;
	constexpr const char RtpStreamId::kUri[];

	constexpr RTPExtensionType RepairedRtpStreamId::kId;
	constexpr const char RepairedRtpStreamId::kUri[];

	constexpr RTPExtensionType RtpMid::kId;
	constexpr const char RtpMid::kUri[];

	} // namespace webrtc