Content rate control for streaming media servers
View Patent ↗The present invention provides a method for content rate selection. The method includes selecting a content rate for play out of at least one frame transmitted from a media server to a media client via a wireless access network. Selection of the content rate is performed based on a statistical representation of a bandwidth available for transmission of frames.
1. An apparatus, comprising:
a media server to select a content rate for play out of at least one frame transmitted from the media server to a media client via a wireless access network, wherein:
the media server is to select one of a plurality of available content rates based on a statistical representation of a bandwidth available for transmission of said at least one frame when the media server is operating in a first mode; and
the media server is to select a lowest available content rate from the plurality of available content rates when the media server is operating in a second mode.
2. The apparatus of claim 1 , wherein the media server is operated in the first mode upon a determination that (a) a buffer level at the client is above a threshold level or (b) an amount by which a presentation timestamp for a latest frame delivered from the media server to the media client exceeds a presentation time stamp for a most recent frame played by the media client.
3. The apparatus of claim 2 , wherein the media server is to determine a plurality of probabilities of buffer underflow at the media client, each of the plurality of probabilities being determined under an assumption that said at least one frame is encoded using a corresponding one of the plurality of available content rates.
4. The apparatus of claim 3 , wherein the media server is to determine the plurality of probabilities of buffer underflow at the media client based on the statistical representation of the bandwidth available for transmission of said at least one frame.
5. The apparatus of claim 3 , wherein the media server is to determine a plurality of probabilities of buffer underflow occurring at the media client within a selected time horizon.
6. The apparatus of claim 3 , wherein the media server is to select one of the plurality of available content rates when the probability of buffer underflow at the media client for the selected one of the plurality of available content rates falls below a threshold.
7. The apparatus of claim 1 , wherein the media server is to determine the statistical representation of the bandwidth available for transmission of said at least one frame.
8. The apparatus of claim 7 , wherein the media server is to determine an aggregate capacity available for transmission of information.
9. The apparatus of claim 8 , wherein the media server is to determine the aggregate capacity based on a mean channel bandwidth over a channel condition feedback interval and a standard deviation associated with the mean channel bandwidth.
10. The apparatus of claim 9 , wherein the media server is to determine a statistical representation of a payload associated with said at least one frame.
11. The apparatus of claim 10 , wherein the media server is to determine at least one of a mean frame size and a standard deviation of the frame size for at least one content rate.
12. The apparatus of claim 11 , wherein the media server is to estimate a payload associated with said at least one frame based on at least one of the mean frame size and the standard deviation of the frame size for the at least one content rate.
13. The apparatus of claim 1 , wherein the media server is operated in the second mode when the media server estimates a buffer level at the client is below a first threshold level or when the media server calculates that the difference between a presentation timestamp for a latest frame delivered from the media server to the media client and a presentation timestamp for a most recent frame played by the media client is below a first threshold time.
14. The apparatus of claim 13 , wherein the media server is transitioned from the second mode to the first mode when the media server estimates the buffer level at the client is above a second threshold level or when the media server calculates that the difference between the presentation timestamps for the latest frame delivered from the media server to the media client and the most recent frame played by the media client is above a second threshold time.
15. The apparatus of claim 14 , wherein the first threshold level is smaller than the second threshold level and wherein the first threshold time is shorter than the second threshold time.
16. The apparatus of claim 1 , wherein the media server is to encode at least one frame based on the selected content rate and transmitting said at least one frame over an air interface.