blob: cfa59d6f2df6bfea42f665095da30cdce3af7bc8 [file] [log] [blame]
/*
* 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/rtcp_packet/rpsi.h"
#include "webrtc/base/checks.h"
#include "webrtc/base/logging.h"
#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
#include "webrtc/modules/rtp_rtcp/source/rtcp_packet/common_header.h"
#include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
using webrtc::RtpUtility::Word32Align;
namespace webrtc {
namespace rtcp {
constexpr uint8_t Rpsi::kFeedbackMessageType;
// RFC 4585: Feedback format.
// Reference picture selection indication (RPSI) (RFC 4585).
//
// 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
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |V=2|P| RPSI=3 | PT=PSFB=206 | length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 0 | SSRC of packet sender |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 4 | SSRC of media source |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 8 | Padding Bits |
// 9 |0| Payload Type|
// 10 | Native RPSI bit string :
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// : defined per codec ... | Padding (0) |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
namespace {
constexpr size_t kPaddingSizeOffset = 8;
constexpr size_t kPayloadTypeOffset = 9;
constexpr size_t kBitStringOffset = 10;
constexpr size_t kPidBits = 7;
// Calculates number of bytes required to store given picture id.
uint8_t RequiredBytes(uint64_t picture_id) {
uint8_t required_bytes = 0;
uint64_t shifted_pid = picture_id;
do {
++required_bytes;
shifted_pid >>= kPidBits;
} while (shifted_pid > 0);
return required_bytes;
}
} // namespace
Rpsi::Rpsi()
: payload_type_(0),
picture_id_(0),
block_length_(CalculateBlockLength(1)) {}
bool Rpsi::Parse(const CommonHeader& packet) {
RTC_DCHECK_EQ(packet.type(), kPacketType);
RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);
if (packet.payload_size_bytes() < kCommonFeedbackLength + 4) {
LOG(LS_WARNING) << "Packet is too small to be a valid RPSI packet.";
return false;
}
ParseCommonFeedback(packet.payload());
uint8_t padding_bits = packet.payload()[kPaddingSizeOffset];
if (padding_bits % 8 != 0) {
LOG(LS_WARNING) << "Unknown rpsi packet with fractional number of bytes.";
return false;
}
size_t padding_bytes = padding_bits / 8;
if (padding_bytes + kBitStringOffset >= packet.payload_size_bytes()) {
LOG(LS_WARNING) << "Too many padding bytes in a RPSI packet.";
return false;
}
size_t padding_offset = packet.payload_size_bytes() - padding_bytes;
payload_type_ = packet.payload()[kPayloadTypeOffset] & 0x7f;
picture_id_ = 0;
for (size_t pos = kBitStringOffset; pos < padding_offset; ++pos) {
picture_id_ <<= kPidBits;
picture_id_ |= (packet.payload()[pos] & 0x7f);
}
// Required bytes might become less than came in the packet.
block_length_ = CalculateBlockLength(RequiredBytes(picture_id_));
return true;
}
bool Rpsi::Create(uint8_t* packet,
size_t* index,
size_t max_length,
RtcpPacket::PacketReadyCallback* callback) const {
while (*index + BlockLength() > max_length) {
if (!OnBufferFull(packet, index, callback))
return false;
}
size_t index_end = *index + BlockLength();
CreateHeader(kFeedbackMessageType, kPacketType, HeaderLength(), packet,
index);
CreateCommonFeedback(packet + *index);
*index += kCommonFeedbackLength;
size_t bitstring_size_bytes = RequiredBytes(picture_id_);
size_t padding_bytes =
Word32Align(2 + bitstring_size_bytes) - (2 + bitstring_size_bytes);
packet[(*index)++] = padding_bytes * 8;
packet[(*index)++] = payload_type_;
// Convert picture id to native bit string (defined by the video codec).
for (size_t i = bitstring_size_bytes - 1; i > 0; --i) {
packet[(*index)++] =
0x80 | static_cast<uint8_t>(picture_id_ >> (i * kPidBits));
}
packet[(*index)++] = static_cast<uint8_t>(picture_id_ & 0x7f);
constexpr uint8_t kPadding = 0;
for (size_t i = 0; i < padding_bytes; ++i)
packet[(*index)++] = kPadding;
RTC_CHECK_EQ(*index, index_end);
return true;
}
void Rpsi::SetPayloadType(uint8_t payload) {
RTC_DCHECK_LE(payload, 0x7f);
payload_type_ = payload;
}
void Rpsi::SetPictureId(uint64_t picture_id) {
picture_id_ = picture_id;
block_length_ = CalculateBlockLength(RequiredBytes(picture_id_));
}
size_t Rpsi::CalculateBlockLength(uint8_t bitstring_size_bytes) {
return RtcpPacket::kHeaderLength + Psfb::kCommonFeedbackLength +
Word32Align(2 + bitstring_size_bytes);
}
} // namespace rtcp
} // namespace webrtc