/// <summary>
/// Parses RTP compound packet.
/// </summary>
/// <param name="buffer">Data buffer..</param>
/// <param name="count">Number of bytes in the <b>buffer</b>.</param>
/// <returns>Returns parsed RTP packet.</returns>
public static RTCP_CompoundPacket Parse(byte[] buffer, int count)
{
/* Compound packet stucture:
* Encryption prefix
* If and only if the compound packet is to be encrypted, it is prefixed by a
* random 32-bit quantity redrawn for every compound packet transmitted.
*
* SR or RR
* The first RTCP packet in the compound packet must always be a report
* packet to facilitate header validation as described in Appendix A.2.
* This is true even if no data has been sent nor received, in which case an
* empty RR is sent, and even if the only other RTCP packet in the compound packet is a BYE.
*
* Additional RRs
* If the number of sources for which reception statistics are being reported
* exceeds 31, the number that will fit into one SR or RR packet, then additional
* RR packets should follow the initial report packet.
*
* SDES
* An SDES packet containing a CNAME item must be included in each compound RTCP packet.
* Other source description items may optionally be included if required by a particular
* application, subject to bandwidth constraints (see Section 6.2.2).
*
* BYE or APP
* Other RTCP packet types, including those yet to be defined, may follow in any order,
* except that BYE should be the last packet sent with a given SSRC/CSRC.
* Packet types may appear more than once.
*/
int offset = 0;
RTCP_CompoundPacket packet = new RTCP_CompoundPacket();
while (offset < count)
{
try{
packet.m_pPackets.Add(RTCP_Packet.Parse(buffer, ref offset));
}
catch {
// Skip invalid or unknown packets.
}
}
return(packet);
}
/// <summary>
/// Validates RTCP compound packet.
/// </summary>
/// <exception cref="ArgumentException">Is raised when invalid RTCP compound packet.</exception>
public void Validate()
{
/* RFC 3550 A.2 RTCP Header Validity Checks.
* The following checks should be applied to RTCP packets.
*
* o RTP version field must equal 2.
*
* o The payload type field of the first RTCP packet in a compound
* packet must be equal to SR or RR.
*
* o The padding bit (P) should be zero for the first packet of a
* compound RTCP packet because padding should only be applied, if it
* is needed, to the last packet.
*
* o The length fields of the individual RTCP packets must add up to
* the overall length of the compound RTCP packet as received. This
* is a fairly strong check.
*/
if (m_pPackets.Count == 0)
{
throw new ArgumentException("No RTCP packets.");
}
// Check version and padding.
for (int i = 0; i < m_pPackets.Count; i++)
{
RTCP_Packet packet = m_pPackets[i];
if (packet.Version != 2)
{
throw new ArgumentException("RTP version field must equal 2.");
}
if (i < (m_pPackets.Count - 1) && packet.IsPadded)
{
throw new ArgumentException("Only the last packet in RTCP compound packet may be padded.");
}
}
// The first RTCP packet in a compound packet must be equal to SR or RR.
if (m_pPackets[0].Type != RTCP_PacketType.SR || m_pPackets[0].Type != RTCP_PacketType.RR)
{
throw new ArgumentException("The first RTCP packet in a compound packet must be equal to SR or RR.");
}
}