Video stream preview

1. A computer-implemented method comprising:

receiving, by a session system from a user device, a request for a video stream preview representing a quality of video data provided by a session host for guiding a user to select a target session host;

generating, by the session system, a test payload of data;

transmitting, by the session system to the user device, the test payload of data that was generated by the session system, wherein the test payload of data is transmitted over a network at a faster rate than a rate at which the video data is to be streamed to the user device;

determining, by the session system, a first measure of network transmission quality for data transmitted over the network from the session system to the user device based on a result of transmitting the test payload to the user device over the network from the session system;

determining, by the session system, a second measure of network transmission quality for data transmitted over the network from the session host to the session system;

estimating, by the session system, an aggregated network transmission quality for data transmitted from the session host to the user device based on the first measure of network transmission quality and the second measure of network transmission quality;

generating, by the session system, the video stream preview according to the aggregated network transmission quality; and

providing, by the session system to the user device, the video stream preview.

2. The method of claim 1 , wherein transmitting the test payload of data from the session system to the user device over the network comprises transmitting the test payload of data using a reliable communication protocol.

3. The method of claim 1 , further comprising providing the video stream preview to the user device using a reliable communication protocol.

4. The method of claim 1 , wherein the second measure of transmission quality is based on a previously computed measure of historical transmission quality from the session host to the session system.

5. The method of claim 4 , wherein the first measure of transmission quality is determined in response to the request for a video stream preview.

6. The method of claim 1 , further comprising:

receiving a second test payload from the session host,

wherein determining the second measure of transmission quality for data provided from the session host to the session system comprises determining the second measure of transmission quality based on a result of receiving the second test payload from the session host.

7. The method of claim 1 , wherein the generated test payload of data has a size corresponding to a particular duration of video of a particular quality.

8. The method of claim 1 , wherein the video stream preview represents a prediction of a video stream to be transmitted over the network from the session host to the user device through the session system.

9. A computer-implemented method comprising:

receiving, by a session system from a user device, a request for a video stream preview representing a quality of video data provided by a session host for guiding a user to select a target session host;

receiving, by the session system, a test payload of data from the user device over a network, wherein the payload of data is transmitted at a faster rate than a rate at which the video data is to be streamed from the user device to the session system;

determining, by the session system, a first measure of network transmission quality for data transmitted over the network from the user device to the session system based on a result of receiving the test payload from the user device over the network;

determining, by the session system, a second measure of network transmission quality for data transmitted over the network from the session system to the session host;

estimating, by the session system, an aggregated network transmission quality for data transmitted from the session host to the user device based on the first measure of network transmission quality and the second measure of network transmission quality;

generating, by the session system, the video stream preview according to the aggregated network transmission quality; and

providing, by the session system to the user device, the video stream preview.

10. The method of claim 9 , wherein receiving the test payload of data from the user device over the network comprises receiving the test payload of data using a reliable communication protocol.

11. The method of claim 9 , further comprising providing the video stream preview to the user device using a reliable communication protocol.

12. The method of claim 9 , wherein the second measure of transmission quality is based on a previously computed measure of historical transmission quality from the session system to the session host.

13. The method of claim 12 , wherein the first measure of transmission quality is determined in response to the request for the video stream preview.

14. The method of claim 9 , further comprising:

providing a second test payload to the session host,

wherein determining the second measure of transmission quality for data provided to the session host from the session system comprises determining the second measure of transmission quality based on a result of providing the second test payload to the session host.

15. The method of claim 9 , wherein the generated test payload of data has a size corresponding to a particular duration of video of a particular quality.

16. The method of claim 9 , wherein the video stream preview represents a prediction of a video stream to be transmitted over the network from the user device to the session host through the session system.

17. A system comprising:

one or more computers and one or more storage devices, including at least one computer and at least one storage device implementing a session system, the one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:

receiving, by the session system from a user device, a request for a video stream preview representing a quality of video data provided by a session host for guiding a user to select a target session host;

generating, by the session system, a test payload of data;

transmitting, by the session system to the user device, the test payload of data that was generated by the session system, wherein the test payload of data is transmitted over a network at a faster rate than a rate at which the video data is to be streamed to the user device;

determining, by the session system, a first measure of network transmission quality for data transmitted over the network from the session system to the user device, based on a result of transmitting the test payload to the user device over the network from the session system;

determining, by the session system, a second measure of network transmission quality for data transmitted over the network from the session host to the session system;

estimating, by the session system, an aggregated network transmission quality for data transmitted from the session host to the user device based on the first measure of network transmission quality and the second measure of network transmission quality;

generating, by the session system, the video stream preview according to the aggregated network transmission quality; and

providing, by the session system to the user device, the video stream preview.

18. The system of claim 17 , wherein transmitting the test payload of data from the session system to the user device over the network comprises transmitting the test payload of data using a reliable communication protocol.

19. The system of claim 17 , wherein the operations further comprise providing the video stream preview to the user device using a reliable communication protocol.

20. The system of claim 17 , wherein the second measure of transmission quality is based on a previously computed measure of historical transmission quality from the session host to the session system.

21. The system of claim 20 , wherein the first measure of transmission quality is determined in response to the request for a video stream preview.

22. The system of claim 17 , wherein the operations further comprise:

receiving a second test payload from the session host,

wherein determining the second measure of transmission quality for data provided from the session host to the session system comprises determining the second measure of transmission quality based on a result of receiving the second test payload from the session host.

23. The system of claim 17 , wherein the generated test payload of data has a size corresponding to a particular duration of video of a particular quality.

24. The system of claim 17 , wherein the video stream preview represents a prediction of a video stream to be transmitted over the network from the session host to the user device through the session system.

25. A system comprising:

one or more computers and one or more storage devices, including at least one computer and at least one storage device implementing a session system, the one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:

receiving, by the session system from a user device, a request for a video stream preview representing a quality of video data provided by a session host for guiding a user to select a target session host;

receiving, by the session system, a test payload of data from the user device over a network, wherein the payload of data is transmitted at a faster rate than a rate at which the video data is to be streamed from the user device to the session system;

determining, by the session system, a first measure of network transmission quality for data transmitted over the network from the user device to the session system based on a result of receiving the test payload from the user device over the network;

determining, by the session system, a second measure of network transmission quality for data transmitted over the network from the session system to the session host;

estimating, by the session system, an aggregated network transmission quality for data transmitted from the session host to the user device based on the first measure of network transmission quality and the second measure of network transmission quality;

generating, by the session system, the video stream preview according to the aggregated network transmission quality; and

providing, by the session system to the user device, the video stream preview.

26. The system of claim 25 , wherein receiving the test payload of data from the user device over the network comprises receiving the test payload of data using a reliable communication protocol.

27. The system of claim 25 , wherein the operations further comprise providing the video stream preview to the user device using a reliable communication protocol.

28. The system of claim 25 , wherein the second measure of transmission quality is based on a previously computed measure of historical transmission quality from the session system to the session host.

29. The system of claim 28 , wherein the first measure of transmission quality is determined in response to the request for a video stream preview.

30. The system of claim 25 , wherein the operations further comprise:

providing a second test payload to the session host,

wherein determining the second measure of transmission quality for data provided to the session host from the session system comprises determining the second measure of transmission quality based on a result of providing the second test payload to the session host.

31. The system of claim 25 , wherein the generated test payload of data has a size corresponding to a particular duration of video of a particular quality.

32. The system of claim 25 , wherein the video stream preview represents a prediction of a video stream to be transmitted over the network from the user device to the session host through the session system.