Apparatus and method for media transmission bandwidth control using bandwidth estimation

1. A method for determining, by a receiving station, an estimated available bandwidth for transmitting a media stream over a network from a transmitting station to the receiving station, the method comprising:

receiving a plurality of frames from the media stream at the receiving station;

determining an inter-arrival time differential d for each frame from the plurality of frames, the inter-arrival time differential d i , for a current frame i calculated as the difference between a network transmission time of the current frame i and a network transmission time of a previous frame i-1 according to d i =(t i −t i-1 )−(T i −T i-1 ), wherein

t i , is a receive time, at the receiving station, of the current frame i,

t i−1 is a receive time, at the receiving station, of the previous frame i-1 that immediately precedes the current frame i,

T i , is a timestamp of the current frame i, and

T i−1 is a timestamp of the previous frame i-1;

determining an inter-frame size differential dL for each frame from the plurality of frames, the inter-frame size differential dL i , for the current frame i calculated as the difference between a frame size of the current frame i and a frame size of the previous frame i-1 according to dL i =L i −L i−1 , wherein

L i is the frame size of frame i, and

L i−1 is the frame size of frame i-1;

determining an estimated function by an adaptive filter that uses the inter-arrival time differential d for each frame from the plurality of frames and the inter-frame size differential dL for each frame from the plurality of frames as inputs, the estimated function having a slope C i −1 and an offset m i , wherein the slope C i −1 represents an inverse capacity of the network with respect to the plurality of frames and the offset m i represents a deviation from a steady-state condition with respect to the plurality of frames; and

determining the estimated available bandwidth based on a comparison between the offset m i and one or more thresholds.

2. The method of claim 1 , wherein determining the estimated available bandwidth comprises:

determining the estimated available bandwidth by increasing a previously determined estimated available bandwidth if a network over-use has not yet been detected during transmission of the media stream.

3. The method of claim 2 , wherein determining the estimated available bandwidth further comprises:

detecting a network over-use if the offset m i exceeds an over-use threshold for at least one of a first pre-determined number of seconds or a first pre-determined number of frames; and

determining the estimated available bandwidth based on a fraction of a bitrate of the media stream when the network over-use is detected.

4. The method of claim 3 , wherein determining the estimated available bandwidth further comprises:

detecting a network under-use if the offset m i is less than an under-use threshold for at least one of a second pre-determined number of seconds or a second pre-determined number of frames; and

determining the estimated available bandwidth as equal to the previously determined estimated available bandwidth.

5. The method of claim 4 , wherein determining the estimated available bandwidth further comprises:

detecting a return to a steady-state range from a previously detected network under-use when the offset m i exceeds the under-use threshold; and

determining the estimated available bandwidth as a maximum bitrate of the media stream measured during the previously detected network under-use.

6. The method of claim 5 , wherein determining the estimated available bandwidth further comprises:

determining the estimated available bandwidth by increasing a previously determined estimated bandwidth if the return to the steady-state range was previously detected.

7. The method of claim 6 , wherein determining the estimated available bandwidth further comprises:

limiting the determined estimated available bandwidth to a maximum value equal to 150% of the bitrate of the media stream.

8. The method of claim 1 , further comprising:

sending the determined estimated available bandwidth to a transmitting station.

9. The method of claim 8 , further comprising:

updating the determined estimated available bandwidth based on a measure of packets lost while transmitting the media stream.

10. The method of claim 9 , wherein updating the determined estimated available bandwidth comprises:

determining a send-side estimated available bandwidth based on a previously determined send-side estimated available bandwidth, wherein:

the send-side estimated available bandwidth is an increase of the previously determined send-side estimated available bandwidth if the measure of packets lost is less than a first packet loss threshold,

the send-side estimated available bandwidth is a decrease of the previously determined send-side estimated available bandwidth if the measure of packets lost is greater than a second packet loss threshold, and

the send-side estimated available bandwidth is otherwise equal to the previously determined send-side estimated available bandwidth; and

updating the determined estimated available bandwidth as the send-side estimated available bandwidth, the updated estimated available bandwidth limited by at least one of an upper bound equal to the determined estimated available bandwidth or a lower bound defined using TCP Friendly Rate Control.

11. The method of claim 10 , further comprising:

determining a target bitrate using the updated estimated available bandwidth; and

encoding the media stream using the target bitrate before transmitting the media stream.

12. The method of claim 1 , wherein the media stream is transmitted over the network using RTP and the determined estimated available bandwidth is sent using RTCP.

13. A method of regulating a bitrate of a media stream encoded by a transmitting station based on an estimated available bandwidth of a network determined by a receiving station, the method comprising:

receiving a plurality of frames from the media stream by the receiving station, the plurality of frames each having an inter-arrival time differential d i and an inter-frame size differential dL i , the inter-arrival time for each frame given by d i =(t i −t i−1 )−(T i −T i−1 ), wherein

t i is a receive time of a current frame i,

t i−1 is a receive time of the previous frame i-1 that immediately precedes the current frame i,

T i is a timestamp of the current frame i, and

T i−1 is a timestamp of the previous frame i-1, and

the inter-frame size differential for each frame given by dL i =L i −L i−1 , wherein

L i is the frame size of frame i, and

L i− is the frame size of frame i-1;

estimating a relationship between the inter-arrival time differential and the inter-frame size differential by an adaptive filter that uses the inter-arrival time differential d i for each frame from the plurality of frames and the inter-frame size differential dL i for each frame from the plurality of frames as inputs and determines a function having a slope C i −1 and an offset m i wherein the slope C i −1 represents an inverse capacity of the network with respect to the plurality of frames and the offset m i represents a deviation from a steady-state condition with respect to the plurality of frames;

detecting an available bandwidth over-use if the offset m i is greater than a positive threshold;

detecting an available bandwidth under-use if the offset m i is less than a negative threshold;

determining the estimated available bandwidth based on whether there is a detected over-use or under-use using a processor; and

regulating the bitrate of the encoded media stream by sending the estimated available bandwidth to the transmitting station.

14. The method of claim 13 , wherein determining the estimated available bandwidth comprises:

determining the estimated available bandwidth based on an increase of a previously determined estimated available bandwidth if neither an over-use or an under-use is detected.

15. The method of claim 13 , wherein determining the estimated available bandwidth comprises:

determining the estimated available bandwidth based on a decrease of a bitrate of the transmitted media stream if an over-use is detected or if an over-use was previously detected and an under-use has not been detected after the over-use detection.

16. The method of claim 13 , wherein determining the estimated available bandwidth comprises:

determining the estimated available bandwidth by maintaining the estimated available bandwidth at a constant value if an under-use is detected, the constant value defined as an estimated available bandwidth previously determined just prior to the under-use detection.

17. The method of claim 13 , wherein regulating the bitrate of the encoded media stream comprises:

sending the estimated available bandwidth to the transmitting station;

determining a bitrate for encoding at least some subsequent frames of the media stream using the estimated available bandwidth; and

encoding the at least some subsequent frames of the media stream using the determined bitrate.

18. A method for estimating, at a receiving station, available bandwidth for transmitting a media stream over a network from a transmitting station to the receiving station, the method comprising:

receiving a plurality of frames from the media stream at the receiving station, each frame of the plurality of frames having an inter-frame size differential dL i and an inter-arrival time differential d i , the inter-arrival time for each frame given by d i =(t i −t i−1 )−(T i −T i−1 ) , wherein

t i is a receive time, at the receiving station, of a current frame i,

t i−1 is a receive time, at the receiving station, of the previous frame i-1 that immediately precedes the current frame i,

T i , is a timestamp of the current frame i, and

T i−1 is a timestamp of the previous frame i-1, and the inter-frame size differential for each frame given by dL i =L i −L i−1 , wherein

L i is the frame size of frame i, and

L i−1 is the frame size of frame i-1;

determining an estimated function by an adaptive filter that uses the inter-arrival time differential for each frame from the plurality of frames and the inter-frame size differential for each frame from the plurality of frames as inputs, the estimated function having a slope C i −1 and an offset m i , wherein the slope C i −1 represents an inverse capacity of the network with respect to the plurality of frames and the offset m i represents a deviation from a steady-state condition with respect to the plurality of frames;

determining a steady-state range using the slope C i −1 of the estimated function and at least one pre-determined threshold value;

detecting if at least some of the inter-arrival time differentials are outside of a steady-state range using at least some of the inter-frame size differentials; and

estimating an available bandwidth based on the detection using a processor.

19. The method of claim 18 , wherein estimating the available bandwidth comprises:

if the estimated function is within the steady-state range:

identifying a previously estimated available bandwidth, and

estimating the available bandwidth by increasing the previously estimated available bandwidth.

20. The method of claim 18 , wherein estimating the available bandwidth comprises:

if the estimated function is greater than the steady-state range:

identifying a bitrate of the media stream, and

estimating the available bandwidth as a percentage of the bitrate.

21. The method of claim 18 , wherein estimating the available bandwidth comprises:

if the estimated function is less than the steady-state range:

identifying a previously estimated available bandwidth, and

estimating the available bandwidth as the previously estimated available bandwidth.

22. A computing device for estimating available bandwidth for transmitting a media stream over a network, the computing device comprising:

a memory; and

a processor configured to execute instructions stored in the memory to:

receive a plurality of frames from the media stream, each frame of the plurality of frames having an inter-frame size differential dL i and an inter-arrival time differential d i , the inter-arrival time for each frame given by d i =(t i −t i−1 )−(T i −T i−1 ) , wherein

t i is a receive time of a current frame i,

t i−1 is a receive time of the previous frame i-1 that immediately precedes the current frame i,

T i is a timestamp of the current frame i, and

T i− is a timestamp of the previous frame i-1, and

the inter-frame size differential for each frame given by dL i =L i −L i−1 , wherein

L i is the frame size of frame i, and

L i−1 is the frame size of frame i-1;

determine an estimated function by an adaptive filter that uses the inter-arrival time differential d for each frame from the plurality of frames and the inter-frame size differential dL for each frame from the plurality of frames as inputs, the estimated function having a slope C i −1 and an offset m i , wherein the slope C i −1 represents an inverse capacity of the network with respect to the plurality of frames and the offset m i represents a deviation from a steady-state condition with respect to the plurality of frames;

determine a steady-state range using the slope C i −1 of the estimated function and at least one pre-determined threshold value;

detect whether at least some of the inter-arrival time differentials are outside of the steady-state range using at least some of the inter-frame size differentials; and

estimate an available bandwidth based on the detection.

23. A computing device for estimating available bandwidth for transmitting a media stream over a network, the computing device comprising:

an RTP receiver configured to receive a plurality of frames from the media stream over the network, each frame having an inter-arrival time differential d i and an inter-frame size differential dL i , the inter-arrival time for each frame given by d i =(t i −t i−1 )−(T i −T i−1 ) , wherein

t i is a receive time of a current frame i,

t i−1 is a receive time of the previous frame i-1 that immediately precedes the current frame i,

T i is a timestamp of the current frame i, and

T i−1 is a timestamp of the previous frame i-1, and

the inter-frame size differential for each frame given by dL i =L i −L i−1 , wherein

L i is the frame size of frame i, and

L i−1 is the frame size of frame i-1;

an adaptive filter configured to determine an estimated function of a relationship between the inter-arrival time differential and the inter-frame size differential based on inter-arrival time differential and inter-frame size differential for the plurality of frames, the estimated function having a slope and an offset;

an over-use detector configured to detect an over-use or under-use of the network based on a comparison between the offset and one or more pre-determined thresholds; and

a remote rate-control configured to determine an estimated available bandwidth based on the detection of an over-use or under-use by the over-use detector.

24. The computing device of claim 23 , wherein the slope of the estimated function represents an inverse capacity of the network with respect to the plurality of frames and the offset represents a deviation from a steady-state condition with respect to the plurality of frames.