public class RtcpIntervalCalculator extends Object
| Modifier and Type | Field and Description |
|---|---|
static double |
INITIAL_MIN_TIME
Initial delay imposed before the first compound RTCP packet is sent.
|
static double |
MIN_TIME
The minimum interval between transmissions of compound RTCP packets.
|
| Constructor and Description |
|---|
RtcpIntervalCalculator() |
| Modifier and Type | Method and Description |
|---|---|
static long |
calculateInterval(boolean initial,
boolean weSent,
int senders,
int members,
double rtcpAvgSize,
double rtcpBw,
double rtcpBwFraction,
double senderBwFraction,
double receiverBwFraction)
6.3.1 - Computing the RTCP Transmission Interval
|
public static final double MIN_TIME
public static final double INITIAL_MIN_TIME
public static long calculateInterval(boolean initial,
boolean weSent,
int senders,
int members,
double rtcpAvgSize,
double rtcpBw,
double rtcpBwFraction,
double senderBwFraction,
double receiverBwFraction)
To maintain scalability, the average interval between packets from a session participant should scale with the group size. This interval is called the calculated interval. It is obtained by combining a number of the pieces of state described above. The calculated interval T is then determined as follows:
1. If the number of senders is less than or equal to 25% of the membership (members), the interval depends on whether the participant is a sender or not (based on the value of we_sent). If the participant is a sender (we_sent true), the constant C is set to the average RTCP packet size (avg_rtcp_size) divided by 25% of the RTCP bandwidth (rtcp_bw), and the constant n is set to the number of senders. If we_sent is not true, the constant C is set to the average RTCP packet size divided by 75% of the RTCP bandwidth. The constant n is set to the number of receivers (members - senders). If the number of senders is greater than 25%, senders and receivers are treated together. The constant C is set to the average RTCP packet size divided by the total RTCP bandwidth and n is set to the total number of members. As stated in Section 6.2, an RTP profile MAY specify that the RTCP bandwidth may be explicitly defined by two separate parameters (call them S and R) for those participants which are senders and those which are not. In that case, the 25% fraction becomes S/(S+R) and the 75% fraction becomes R/(S+R). Note that if R is zero, the percentage of senders is never greater than S/(S+R), and the implementation must avoid division by zero.
2. If the participant has not yet sent an RTCP packet (the variable initial is true), the constant Tmin is set to 2.5 seconds, else it is set to 5 seconds.
3. The deterministic calculated interval Td is set to max(Tmin, n*C).
4. The calculated interval T is set to a number uniformly distributed between 0.5 and 1.5 times the deterministic calculated interval.
5. The resulting value of T is divided by e-3/2=1.21828 to compensate for the fact that the timer reconsideration algorithm converges to a value of the RTCP bandwidth below the intended average.
This procedure results in an interval which is random, but which, on average, gives at least 25% of the RTCP bandwidth to senders and the rest to receivers. If the senders constitute more than one quarter of the membership, this procedure splits the bandwidth equally among all participants, on average.
initial - weSent - senders - members - rtcpAvgSize - rtcpBw - rtcpBwFraction - Copyright © 2017 TeleStax, Inc.. All Rights Reserved.