/// <summary>
/// Sets property LastRR value.
/// </summary>
/// <param name="rr">RTCP RR report.</param>
/// <exception cref="ArgumentNullException">Is raised when <b>rr</b> is null reference.</exception>
internal void SetRR(RTCP_Packet_ReportBlock rr)
{
if (rr == null)
{
throw new ArgumentNullException("rr");
}
}
/// <summary>
/// Parses receiver report(RR) from byte buffer.
/// </summary>
/// <param name="buffer">Buffer wihich contains receiver report.</param>
/// <param name="offset">Offset in buufer.</param>
/// <exception cref="ArgumentNullException">Is raised when <b>buffer</b> is null.</exception>
/// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
protected override void ParseInternal(byte[] buffer, ref int offset)
{
/* RFC 3550 6.4.2 RR: Receiver Report RTCP Packet.
* 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* header |V=2|P| RC | PT=RR=201 | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of packet sender |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| report | SSRC_1 (SSRC of first source) |
| block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | fraction lost | cumulative number of packets lost |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| extended highest sequence number received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| interarrival jitter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| last SR (LSR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| delay since last SR (DLSR) |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| report | SSRC_2 (SSRC of second source) |
| block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 : ... :
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| profile-specific extensions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
if (offset < 0)
{
throw new ArgumentException("Argument 'offset' value must be >= 0.");
}
m_Version = buffer[offset] >> 6;
bool isPadded = Convert.ToBoolean((buffer[offset] >> 5) & 0x1);
int reportBlockCount = buffer[offset++] & 0x1F;
int type = buffer[offset++];
int length = buffer[offset++] << 8 | buffer[offset++];
if (isPadded)
{
this.PaddBytesCount = buffer[offset + length];
}
m_SSRC = (uint)(buffer[offset++] << 24 | buffer[offset++] << 16 | buffer[offset++] << 8 | buffer[offset++]);
for (int i = 0; i < reportBlockCount; i++)
{
RTCP_Packet_ReportBlock reportBlock = new RTCP_Packet_ReportBlock();
reportBlock.Parse(buffer, offset);
m_pReportBlocks.Add(reportBlock);
offset += 24;
}
// TODO: profile-specific extensions
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="rr">RTCP RR report.</param>
/// <exception cref="ArgumentNullException">Is raised when <b>rr</b> is null reference.</exception>
internal RTCP_Report_Receiver(RTCP_Packet_ReportBlock rr)
{
if (rr == null)
{
throw new ArgumentNullException("rr");
}
m_FractionLost = rr.FractionLost;
m_CumulativePacketsLost = rr.CumulativePacketsLost;
m_ExtHigestSeqNumber = rr.ExtendedHighestSeqNo;
m_Jitter = rr.Jitter;
m_LastSR = rr.LastSR;
m_DelaySinceLastSR = rr.DelaySinceLastSR;
}
/// <summary>
/// Creates receiver report.
/// </summary>
/// <returns>Returns created receiver report.</returns>
internal RTCP_Packet_ReportBlock CreateReceiverReport()
{
/* RFC 3550 A.3 Determining Number of Packets Expected and Lost.
* In order to compute packet loss rates, the number of RTP packets
* expected and actually received from each source needs to be known,
* using per-source state information defined in struct source
* referenced via pointer s in the code below. The number of packets
* received is simply the count of packets as they arrive, including any
* late or duplicate packets. The number of packets expected can be
* computed by the receiver as the difference between the highest
* sequence number received (s->max_seq) and the first sequence number
* received (s->base_seq). Since the sequence number is only 16 bits
* and will wrap around, it is necessary to extend the highest sequence
* number with the (shifted) count of sequence number wraparounds
* (s->cycles). Both the received packet count and the count of cycles
* are maintained the RTP header validity check routine in Appendix A.1.
*
* extended_max = s->cycles + s->max_seq;
* expected = extended_max - s->base_seq + 1;
*
* The number of packets lost is defined to be the number of packets
* expected less the number of packets actually received:
*
* lost = expected - s->received;
*
* Since this signed number is carried in 24 bits, it should be clamped
* at 0x7fffff for positive loss or 0x800000 for negative loss rather
* than wrapping around.
*
* The fraction of packets lost during the last reporting interval
* (since the previous SR or RR packet was sent) is calculated from
* differences in the expected and received packet counts across the
* interval, where expected_prior and received_prior are the values
* saved when the previous reception report was generated:
*
* expected_interval = expected - s->expected_prior;
* s->expected_prior = expected;
* received_interval = s->received - s->received_prior;
* s->received_prior = s->received;
* lost_interval = expected_interval - received_interval;
* if(expected_interval == 0 || lost_interval <= 0)
* fraction = 0;
* else
* fraction = (lost_interval << 8) / expected_interval;
*
* The resulting fraction is an 8-bit fixed point number with the binary
* point at the left edge.
*/
uint extHighestSeqNo = (uint)(m_SeqNoWrapCount << 16 + m_MaxSeqNo);
uint expected = extHighestSeqNo - m_BaseSeq + 1;
int expected_interval = (int)(expected - m_ExpectedPrior);
m_ExpectedPrior = expected;
int received_interval = (int)(m_PacketsReceived - m_ReceivedPrior);
m_ReceivedPrior = m_PacketsReceived;
int lost_interval = expected_interval - received_interval;
int fraction = 0;
if (expected_interval == 0 || lost_interval <= 0)
{
fraction = 0;
}
else
{
fraction = (lost_interval << 8) / expected_interval;
}
RTCP_Packet_ReportBlock rr = new RTCP_Packet_ReportBlock(this.SSRC.SSRC);
rr.FractionLost = (uint)fraction;
rr.CumulativePacketsLost = (uint)this.PacketsLost;
rr.ExtendedHighestSeqNo = extHighestSeqNo;
rr.Jitter = (uint)m_Jitter;
rr.LastSR = (m_pLastSR == null ? 0 : ((uint)((long)m_pLastSR.NtpTimestamp >> 8) & 0xFFFF));
rr.DelaySinceLastSR = (uint)Math.Max(0, this.DelaySinceLastSR / 65.536);
return(rr);
}
