Detecting media rate for measuring network jitter

1. A method, comprising:

receiving a stream of packets of encoded data sent by a transmitter across a network, the stream of packets including n+1 packets having transmittal timestamps from a clock local to the transmitter, n being an integer greater than or equal to one and wherein the stream of packets further includes at least one packet that does not contain a transmittal timestamp from a clock local to the transmitter;

determining an n+1 th transmittal timestamp; determining an nth transmittal timestamp;

determining a number of packets k received between the n+1 th transmittal timestamp and the nth transmittal timestamp;

calculating an expected time interval between consecutive packets based on k and the n+1 th and the nth transmittal timestamps;

using the calculated expected time interval between consecutive packets and a measured time interval between consecutive packets in the stream of packets to calculate a maximum theoretical time interval between consecutive packets; and

calculating a Delay Factor (DF) of a Media Delivery Index (MDI) for the network based on the calculated maximum theoretical time interval between consecutive packets,

wherein calculating an expected time interval per packet based on the n+1 th and the n th transmittal timestamps further comprises:

determining a first difference between the n+1 th and the n th transmittal timestamps

wherein calculating an expected time interval per packet based on k and the n+1 th and the nth transmittal timestamps comprises:

determining a ratio of the first difference to k;

calculating a first factor based on the ratio, wherein the first factor corresponds to a size of a virtual buffer just before arrival of a selected packet; and

calculating a second factor based on the ratio, wherein the second factor corresponds to a size of the virtual buffer just after arrival of the selected packet.

2. A method as in claim 1 , wherein the encoded data is encoded according to the International Standard ISO/IEC 13818-1.

3. A method as in claim 1 , wherein the transmittal timestamps serve as a reference base for decoding the packets at a predetermined time.

4. A method as in claim 3 , wherein the transmittal timestamps are Program Clock References according to the International Standard ISO/IEC 13818-1.

5. A method as in claim 1 , wherein the packets carry data for a streaming video service.

6. A method as in claim 5 , wherein the streaming video service is selected from the group consisting of Internet Protocol television (IPTV), video conferencing, and video-on-demand.

7. A method as in claim 1 , further comprising:

calculating the first and second factors for each packet received, each time a packet having a transmittal timestamp arrives within the measurement interval;

determining a minimum first factor within the measurement interval;

determining a maximum second factor within the measurement interval; determining a second difference between the minimum first factor and the maximum second factor; and

using the second difference as the performance measure for the network.

8. A method as in claim 1 , wherein calculating the first factor is further based on a first arrival time difference between receiving the selected packet, and receiving the packet before the selected packet.

9. A method as in claim 1 , wherein the ratio is determined once within a measurement interval and used a plurality of times in calculating the first and second factors.

10. A method as in claim 1 , further comprising

determining an (n−1) th transmittal timestamp;

calculating a second value based on the (n−1) th transmittal timestamp and the n th transmittal timestamp; and

using the second calculated value to determine the Delay Factor for the network.

11. A method as in claim 10 , wherein calculating a second value is further based on:

determining a second arrival time difference between receiving the packet bearing the (n+1) th transmittal timestamp, and receiving the packet bearing the n th transmittal timestamp.

12. An apparatus, comprising: a receiver that receives a stream of packets of encoded data sent by a transmitter across a network, the stream of packets including n+1 packets having transmittal timestamps from a clock local to the transmitter, n being an integer greater than or equal to zero and wherein the stream of packets further includes at least one packet that does not contain a transmittal timestamp from a clock local to the transmitter;

a parser that parses the stream of packets, extracts an n+1 th transmittal timestamp, and extracts an nth transmittal timestamp;

a clock that clocks an actual arrival time for each packet for determining the actual arrival time between consecutive packets in the stream of packets; and

a processor that determines a number of packets k received between the nth and n+1 th transmittal timestamps and calculates an expected time interval between consecutive packets based on k, and the n+1 th and the n th transmittal timestamps that uses the calculated time interval between consecutive packets and a measured time interval between consecutive packets to calculate a maximum theoretical time interval between consecutive packets, and that calculates a Delay Factor (DF) of a Media Delivery Index (MDI) for the network based on the calculated maximum theoretical time interval between consecutive packets,

wherein calculating an expected time interval per packet based on the n+1 th and the n th transmittal timestamps further comprises:

determining a first difference between the n+1 th and the n th transmittal timestamps

wherein calculating an expected time interval per packet based on k and the n+1 th and the nth transmittal timestamps comprises:

determining a ratio of the first difference to k;

calculating a first factor based on the ratio, wherein the first factor corresponds to a size of a virtual buffer just before arrival of a selected packet; and

calculating a second factor based on the ratio, wherein the second factor corresponds to a size of the virtual buffer just after arrival of the selected packet.

13. An apparatus as in claim 12 , further comprising:

a counter that counts packets from the nth transmittal timestamp to the (n+1) th transmittal timestamp.

14. A method, comprising: receiving a stream of packets of encoded data sent by a transmitter across a network, the stream of packets including a plurality of packets that do not include transmittal timestamps and n+1 packets having transmittal timestamps from a clock local to the transmitter, n being an integer greater than or equal to one and wherein the stream of packets further includes at least one packet does not contain a transmittal timestamp from a clock local to the transmitter;

determining an n+1 th transmittal timestamp;

determining an n th transmittal timestamp;

determining a first difference between the n+1 th and the nth transmittal timestamps;

determining a packet count k from the n th transmittal timestamp to the n+1 th transmittal timestamp;

determining a ratio of the first difference to the packet count;

calculating a first factor based on the ratio, wherein the first factor corresponds to an expected amount of time to drain a virtual buffer just before arrival of a selected packet;

calculating a second factor based on the ratio, wherein the second factor corresponds to an expected amount of time to drain the virtual buffer just after arrival of the selected packet; and

using the first and second factors and an actual inter-arrival time between consecutive packets having transmittal timestamps to determine a Delay Factor (DF) of a Media Delivery Index (MDI) for the network.

15. The method of claim 14 , wherein using the first and second factors to determine a performance measure for the network comprises:

calculating the first and second factors for each packet received, each time a packet having a transmittal timestamp arrives within a measurement interval;

determining a minimum first factor within the measurement interval;

determining a maximum second factor within the measurement interval;

determining a second difference between the minimum first factor and the maximum second factor; and

using the second difference as the performance measure for the network.

16. The method of claim 1 , wherein the transmittal timestamps, comprise program clock reference timestamps.

17. The apparatus of claim 12 , wherein the transmittal timestamps comprise program clock reference timestamps.

18. The method of claim 14 , wherein the transmittal timestamps comprise program clock reference timestamps.