Method and apparatus for caching for streaming data

• US 7,028,096 B1
• Filed: 09/08/2000
• Issued: 04/11/2006
• Est. Priority Date: 09/14/1999
• Status: Expired due to Fees

• Current Assignee: Steaming21 Incorporated, Streaming21, Inc.
• Original Assignee: Streaming21, Inc.
• Inventors: Lee, Horng-Juing
• Primary Examiner(s): Vaughn, Jr., William C.
• Assistant Examiner(s): DENNISON, JERRY B
• Application Number:
  US09/658,705
• Time in Patent Office: 2,041 Days
• Field of Search: 709/213, 709231-236, 725/92, 725/94, 725/115, 725/145
• US Class Current: 709/231
• CPC Class Codes: H04N 21/2183 Cache memory caches in web servers or browsers G06F16/9574; intermediate storage and caching in data networks H04L67/568
• CPC Class Codes: H04N 21/222 Secondary servers, e.g. proxy server, cable television Head-end provisioning of proxy services in data packet switching networks H04L67/56
• CPC Class Codes: H04N 21/2225 Local VOD servers
• CPC Class Codes: H04N 21/23106 involving caching operations prefetching while addressing of a memory level in which the access to the desired data or data block requires associative addressing means within memory systems or architectures G06F12/0862; caching at an intermediate stage in a data network H04L67/568
• CPC Class Codes: H04N 21/2402 Monitoring of the downstream path of the transmission network, e.g. bandwidth available traffic monitoring in data switching networks H04L43/00; monitoring data switching networks utilization H04L43/0876
• CPC Class Codes: H04N 21/64792 Controlling the complexity of the content stream, e.g. by dropping packets intermediate media network packet handling H04L65/765; proxy provisioning conversion or adaptation for reducing the amount or size of exchanged application data H04L67/5651; negotiation of resources in wireless networks H04W28/16
• CPC Class Codes: H04N 7/17336 Handling of requests in head-ends

Abstract

Streaming video data from the video title is delivered to a client from a central server and a proxy server. To reduce the backbone bandwidth required, a portion of the video title is cached at the proxy server where the portion cached is distributed over the video title so as to reduce the peak bit rate required for the central server to send the remaining portion of the video title. The amount cached at the proxy server may be adjusted in accordance with access profile of video titles to improve caching efficiency. The portion cached may be the basic layer in a scalable multilayer approach where only the basic layer may be sent to a client who has limited bandwidth while clients with higher bandwidth capability may also receive the enhancement layer(s) for improved video reception.

Claims

1. A method of caching in a system for transmitting a plurality of media data titles to one or more client(s) from a central server computer system and a proxy server computer system located in a computer network, said proxy server computer system located in the network between the central server computer system and the one or more client(s), wherein each media data title is divided into blocks to be transmitted to the one or more client(s) in a time sequence, and each block is divided into sub-blocks, comprising:

causing the central server computer system to transmit data in the media data titles to the proxy server computer system via a backbone network connection, and the proxy server computer system to transmit data in the media data titles to one or more client(s) via a local network connection;

identifying which sub-blocks from different blocks of each media data title that are to be cached, wherein the identified sub-blocks include some sub-blocks in each of the blocks of at least one media data title;

caching only the identified sub-blocks at the proxy server computer system to reduce the transmission bit rate of the central server computer system in the network for transmitting data in the media data titles to the proxy server computer system; and

combining sub-blocks of a media data title cached at the proxy server computer system with sub-blocks of the media data title not cached at the proxy server computer system and transmitted from the central server computer system to the proxy server computer system through the network, for delivery to the one or more client(s), wherein a peak transmission rate in the backbone network connection for the central server computer system to transmit data in the media data titles to the proxy server computer system is reduced;

wherein the media data titles include video titles and the sub-blocks comprise partial information of video frames, wherein the video frames are to be transmitted sequentially wherein the combining combines the partial information of video frames from the proxy server computer system with complementary partial information of such video frames from the central server computer system into complete video frames and sending the complete video frames to the client(s); and

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, and wherein the combining combines the video information at the lower first sampling rate from the proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

2. The method of claim 1, wherein the cached sub-blocks are cached for time periods that are independent of time.

3. The method of claim 1, wherein the caching caches substantially the same number of sub-blocks from each block of said at least one media data title.

4. The method of claim 1, wherein the partial information comprise video information along some scan lines of video frames, further comprising combining the video information along such scan lines with complementary video information along other scan lines of such video frames from the central server computer system into complete video frames and sending the complete video frames to the client(s).

5. The method of claim 1, wherein the partial information comprise video information in a basic layer and the complementary partial information comprises video information in an enhancement layer, said basic and enhancement layers being defined according to spatial, signal-to-noise or temporal scalability.

6. The method of claim 1, wherein the identifying is made as a function of an access profile of the media data titles at the proxy.

7. The method of claim 1, wherein prior to any accesses of the media data titles by the client(s), an average caching approach utilizes storage at the proxy server computer system by storing a substantially equal number of sub-blocks from each media data title.

8. The method of claim 1, wherein prior to any accesses of the media data titles by the client(s), a proportional caching approach utilizes access history data to determine how much of each media data title to cache.

9. The method of claim 1, wherein after the system starts operation, cache content at the proxy server computer system will change from time to time to reflect actual access behavior.

10. The method of claim 1, further comprising beginning a caching process at the proxy server computer system after receiving a media data-title request from a client by ensuring there is sufficient bandwidth from said proxy to such client to deliver the request and if not, denying the request.

11. The method of claim 10, further comprising delivering the complete content of the requested media data title when such content is in local storage of said proxy server computer system.

12. The method of claim 10, further comprising:

when said proxy server computer system does not have complete content of the requested media data title, determining if there is sufficient available backbone bandwidth to carry said media data title from the central server computer system to said proxy server computer system and if not, rejecting the request.

13. The method of claim 12, further comprising activating a progressive caching process to adjust cache content at said proxy server computer system to reflect the requested media data title.

14. The method of claim 1, further comprising replacing a cached portion of a particular media data title by deleting the most recently cached portion of such media data title.

15. The method of claim 1, further comprising deciding which media data titles shall be subject to caching replacement using a most current access profile as an indication of a future profile.

16. The method of claim 1, further comprising keeping track of each access request at the proxy server computer system in order to determine which media data titles shall be subject to caching replacement.

17. The method of claim 1, further comprising deciding which media data titles shall be subject to caching replacement using a current access profile as an indication of the future profile, wherein said deciding includes:

defining a time window ending at the time of the caching replacement;

calculating an access frequency of each media data title in a storage of the proxy server computer system said access frequency being a function of the accesses to such media data title during the time window or a portion thereof; and

performing the caching replacement in response to the access frequencies of the media data titles in the storage.

18. The method of claim 17, wherein said access frequency is proportional to the sum of the accesses to such media data title during the time window or a portion thereof.

19. The method of claim 17, wherein said access frequency is proportional to a time-weighted sum of the accesses to such media data title during the time window or a portion thereof, with the time weighting in favor of accesses occurring more recently in the window.

20. The method of claim 1, further comprising detecting multiple ongoing requests from clients for a media data title received at different times during caching in response to an initial request of said media data title, and increasing the number of sub-blocks cached from the blocks of at least one media data title in response to a subsequent request of said media data title.

21. A system for delivering media information;

the system comprising;

a plurality of proxy server computer systems, each servicing a number of terminal devices via a local network connection and receiving a request from one of said terminal devices when a user of said one of said terminal devices desires for a media data title among a plurality of media data titles, said media data titles divided into units that are transmitted in a time sequence to one or more of the terminal devices;

each of said proxy server computer systems comprising a cache memory for storing information in units of at least some of the media data titles;

wherein amount of information in the units of each of said at least some media data titles stored or replaced in the cache memory is determined by a request frequency to said each of said media data titles; and

a central server computer system coupled to said proxy server computer systems via a backbone connection in a network, said proxy server computer systems located in the network between the central server computer system and one or more client(s), wherein the central server computer system transmits data in the media data titles to the proxy server computer systems, and each of the proxy server computer systems transmits data in the media data titles to one or more terminal devices;

said central server computer system having a storage space for storing a plurality of said media data titles and providing data from one or more of said media data titles when receiving a proxy request from one of said proxy server computer systems, wherein the units of at least one of said media data titles containing information cached in the cache memory of said one proxy server computer system are divided into sub-blocks, and wherein the sub-blocks stored in the cache memory of said one proxy server computer system include some sub-blocks in each of the units of said at least one media data title;

said one proxy server computer system combining the sub-blocks in cached units with uncached sub-blocks in units received through the network from the central server computer system to form a data stream of complete media data title(s) and transmitting the combined sub-blocks in units of such media data title(s) to one or more terminal devices, so that the transmission bit rate of the central media server computer system in the backbone connection of the network for transmitting data from the at least some media data titles to said one of the proxy server computer systems is reduced,

wherein the media data titles include video titles, and the sub-blocks comprise partial information of video frames, wherein the video frames are to be transmitted sequentially wherein said one proxy server computer system combines the partial information of video frames from the proxy server computer system with complementary partial information of such video frames from the central server computer system into complete video frames and sending the complete video frames to the clients);

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, and wherein said one proxy server computer system combines the video information at the lower first sampling rate from the proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

22. A system for delivering media information;

the system comprising;

a plurality of proxy server computer systems, each servicing a number of terminal devices and receiving a request from one of said terminal devices when a user of said one of said terminal devices desires a media data title from a plurality of media data titles;

wherein at least one of said proxy server computer systems comprises a cache memory; and

a central server computer system coupled to said proxy server computer systems in a network, said proxy server computer systems located in the network between the central server computer system and one or more client(s), wherein the central server computer system transmits data in the media data titles to the proxy server computer systems, and the proxy server computer systems transmit data in the media data titles to one or more client(s);

said central server computer system having a storage space for storing a plurality of said media data titles and providing data from one of said media data titles when receiving a proxy request from said at least one of said proxy server computer systems, said cache memory of said at least one proxy server computer system caching only some of the units of said at least one media data title, said at least one proxy server computer system combining the cached units with uncached units received through the network from the central server computer system to form a data stream of a complete media data title and transmitting such media data title to one or more client(s), so that the transmission bit rate of the central server computer system in the network for transmitting the at least one media data title to said at least one proxy server computer system is reduced, wherein said at least one of said You media data titles includes video frames to be transmitted in a time sequence, each frame being divided into sub-blocks, each of the sub-blocks comprising partial information of a video frame, wherein said units of said at least one media data title cached at said proxy server computer system comprise partial information of substantially all of the video frames in said at least one eel media data title so that said one proxy server computer system combines the cached partial information of substantially all of the video frames in said at least one media data title with complementary partial information of such video frames from the central server computer system into complete video frames and sends the complete video frames to terminal devices;

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, and wherein said one proxy server computer system combines the video information at the lower first sampling rate from said one proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to terminal devices.

23. The system of claim 22, wherein said at least one proxy server computer system stores the units of the at least one media data title for time periods that are independent of time.

24. The system of claim 22, wherein the at least one media data title is divided into blocks to be transmitted to the one or more user(s) in a time sequence, and each block is divided into sub-blocks, wherein the at least one proxy server computer system caches the same number of sub-blocks from each block of said at least one media data title.

25. The system of claim 22, wherein the partial information comprise video information along some scan lines of video frames, and wherein the at least one proxy server computer system combines the video information along such scan lines with complementary video information along other scan lines of such video frames from the central server computer system into complete video frames and sends the complete video frames to the user(s).

26. The system of claim 22, wherein the sub-blocks comprise information in a base layer of a scalable multilayer system.

27. The system of claim 22, where the number of units is a function of an access profile of the at least one media data title at the at least one proxy server computer system.

56. The system of claim 22, wherein the central server computer system transmits data in the media data titles to the at least one proxy server computer system via a backbone network connection, and the at least one proxy server computer system transmits data in the media data titles to one or more client(s) via a local network connection, and wherein a peak transmission rate in the backbone network connection for the central server computer system to transmit data from the at least some media data titles to the at least one proxy server computer system is reduced.

28. A method of caching in a system for transmitting a plurality of media data titles to one or more client(s) from a central server computer system and a proxy server computer system in a network, said proxy server computer system located in the network between the central server computer system and the one or more client(s), wherein each media data title is divided into blocks to be transmitted to the one or more client(s) in a time sequence, and each block is divided into sub-blocks, comprising:

identifying which sub-blocks from different blocks of each media data title that are to be cached, wherein the identified sub-blocks include sub-blocks that are distributed over the blocks of at least one media data title;

caching only the identified sub-blocks at the proxy server computer system to reduce the transmission bit rate of the central server computer system in the network for transmitting data in the media data titles to the proxy server computer system; and

combining sub-blocks of a media data title cached at the proxy server computer system with sub-blocks of the media data title not cached at the proxy server computer system and transmitted from the central server computer system through the network to the proxy server computer system, for delivery to the one or more client(s), wherein the cached sub-blocks of at least one of said media data titles comprise partial information of video frames, wherein the video frames are to be transmitted sequentially, and wherein said one proxy server computer system combines the cached partial information of video frames with complementary partial information of such video frames from the central server computer system into complete video frames and sends the complete video frames to the one or more client(s);

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, and wherein said combining combines the video information at the lower first sampling rate from the proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

29. The method of claim 28, wherein the cached sub-blocks are stored for time periods that are independent of time.

30. The method of claim 28, wherein the caching caches the same number of sub-blocks from each block of said at least one media data title.

57. The method of claim 28, further comprising causing the central server computer system to transmit data in the media data titles to the proxy server computer system via a backbone network connection, and the proxy server computer system to transmit data in the media data titles to one or more client(s) via a local network connection;

wherein a peak transmission rate in the backbone network connection for the central server computer system to transmit data in the media data titles to the proxy server computer system is reduced.

60. The method of claim 28, said sub-blocks of said at least one media data title cached at said proxy server computer system comprise partial information of substantially all of the video frames in said at least one media data title.

31. A computer readable storage device embodying a program of instructions executable by a computer to perform a method of caching in a system for transmitting a plurality of media data titles to one or more client(s) from a central server computer system and a proxy server computer system in a network, said proxy server computer system located in the network between the central server computer system and the one or more client(s), wherein each media data title is divided into blocks to be transmitted to the one or more client(s) in a time sequence, and each block is divided into sub-blocks, said method comprising:

identifying which sub-blocks from different blocks of each media data title that are to be cached, wherein the identified sub-blocks include sub-blocks that are distributed over the blocks of at least one media data title;

caching the identified sub-blocks under the control of the proxy server computer system to reduce the transmission bit rate of the central server computer system in the network for transmitting data in the media data titles to the proxy server computer system; and

combining sub-blocks of a media data title cached at the proxy server computer system with sub-blocks of the media data title not cached at the proxy server computer system and transmitted from the central server computer system through the network to the proxy server computer system, wherein the cached sub-blocks of at least one of said media data titles comprise partial information of video frames, wherein the video frames are transmitted sequentially to the one or more client(s), and wherein said one proxy server computer system combines the cached partial information of video frames with complementary partial information of such video frames from the central server computer system into complete video frames and sends the complete video frames to the one or more client(s);

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, and wherein said combining combines the video information at the lower first sampling rate from the proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

32. The device of claim 31, wherein the cached sub-blocks are stored for time periods that are independent of time.

33. The device of claim 31, wherein the caching caches substantially the same number of sub-blocks from each block of said at least one media data title.

34. The device of claim 31, wherein the partial information comprise video information along some scan lines of video frames, said method further comprising combining the video information along such scan lines with complementary video information along other scan lines of such video frames from the central server computer system into complete video frames and sending the complete video frames to the client(s).

35. The device of claim 31, wherein the partial information comprise video information in a basic layer and the complementary partial information comprises video information in an enhancement layer, said basic and enhancement layers being defined according to spatial, signal-to-noise or temporal scalability.

36. The device of claim 31, wherein the identifying is made as a function of an access profile of the media data titles at the proxy server computer system.

37. The device of claim 31, wherein prior to any accesses of the media data titles by the client(s), an average caching approach utilizes storage at the proxy server computer system by storing a substantially equal number of sub-blocks from each media data title.

38. The device of claim 31, wherein prior to any accesses of the media data titles by the client(s), a proportional caching approach utilizes access history data to determine how much of each media data title to cache.

39. The device of claim 31, wherein after the system starts operation, cache content at the proxy server computer system will change from time to time to reflect actual access behavior.

40. The device of claim 31, said method further comprising beginning a caching process at the proxy server computer system after receiving a media data title request from a client by ensuring there is sufficient bandwidth from said proxy server computer system to such client to deliver the request and if not, denying the request.

41. The device of claim 40, said method further comprising delivering the complete content of the requested media data title when such content is in local storage of said proxy server computer system.

42. The device of claim 40, said method further comprising:

when said proxy server computer system does not have complete content of the requested media data title, determining if there is sufficient available backbone bandwidth to carry said media data title from the central server computer system to said proxy server computer system and if not, rejecting the request.

43. The device of claim 42, said method further comprising activating a progressive caching process to adjust cache content at said proxy server computer system to reflect the requested media data title.

44. The device of claim 31, said method further comprising replacing a cached portion of a particular media data title by deleting the most recently cached portion of such media data title.

45. The device of claim 31, said method further comprising deciding which media data titles shall be subject to caching replacement using a most current access profile as an indication of a future profile.

46. The device of claim 31, said method further comprising keeping track of each access request at the proxy server computer system in order to determine which media data titles shall be subject to caching replacement.

47. The device of claim 31, said method further comprising deciding which media data titles shall be subject to caching replacement using a current access profile as an indication of the future profile, wherein said deciding includes:

defining a time window ending at the time of the caching replacement;

calculating an access frequency of each media data title in a storage of the proxy server computer system, said access frequency being a function of the accesses to such media data title during the time window or a portion thereof; and

performing the caching replacement in response to the access frequencies of the media data titles in the storage.

48. The device of claim 47, wherein said access frequency is proportional to the sum of the accesses to such media data title during the time window or a portion thereof.

49. The device of claim 47, wherein said access frequency is proportional to a time-weighted sum of the accesses to such media data title during the time window or a portion thereof, with the time weighting in favor of accesses occurring more recently in the window.

50. The device of claim 31, said method further comprising detecting multiple ongoing requests from clients for a media data title received at different times during caching in response to an initial request of said media data title, and increasing the number of sub-blocks cached from the blocks of at least one media data title in response to a subsequent request of said media data title.

58. The device of claim 31, said method further comprising causing the central server computer system to transmit data in the media data titles to the proxy server computer system via a backbone network connection, and the proxy server computer system to transmit data in the media data titles to one or more client(s) via a local network connection;

wherein a peak transmission rate in the backbone network connection for the central server computer system to transmit data in the media data titles the proxy server computer system is reduced.

61. The device of claim 31, said sub-blocks of said at least one media data title cached at said proxy server computer system comprise partial information of substantially all of the video frames in said at least one media data title.

51. A method for transmitting a program of instructions executable by a computer to perform a process of caching in a system for transmitting a plurality of media data titles to one or more client(s) from a central server computer system and a proxy server computer system in a network, said proxy server computer system located in the network between the central server computer system and the one or more client(s), wherein each media data title is divided into blocks to be transmitted to the one or more client(s) in a time sequence, and each block is divided into sub-blocks, said method comprising:

transmitting to a client device a program of instructions; and

enabling the client device to perform, by means of such program, the following process;

identifying which sub-blocks from different blocks of each media data title that are to be cached, wherein the identified sub-blocks include sub-blocks that are distributed over the blocks of at least one media data title; and

caching the identified sub-blocks under the control of the proxy server computer system to reduce the transmission bit rate of the central server computer system in the network for transmitting data in the media data titles to the proxy server computer system; and

combining sub-blocks of a media data title cached at the proxy server computer system with sub-blocks of the media data title not cached at the proxy server computer system and transmitted from the central server computer system through the network to the proxy server computer system, for delivery to the one or more client(s), wherein at least one of said media data titles cached includes a media data title divided into blocks to be transmitted in a time sequence, and each block is divided into sub-blocks some of which are cached, and the cached sub-blocks comprise partial information of video frames, wherein the video frames are to be transmitted sequentially, and wherein said proxy server computer system combines the partial information of video frames with complementary partial information of such video frames from the central server computer system into complete video frames and sends the complete video frames to client(s);

wherein the partial information comprise video information obtained at a set of sampling times and at a first sampling rate lower tan that of a video source from which said information originates, and wherein said combining, combines the video information at the lower first sampling rate from the proxy server computer system with complementary video information taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

52. The method of claim 51, wherein the program enables the cached sub-blocks to be stored for time periods that are independent of time.

53. The method of claim 51, wherein the program enables the caching to cache substantially the same number of sub-blocks from each block of said at least one media data title.

54. The method of claim 51, wherein the partial information comprise video information in a basic layer and the complementary partial information comprises video information in an enhancement layer, said basic and enhancement layers being defined according to spatial, signal-to-noise or temporal scalability.

55. The method of claim 51, wherein the identifying is made as a function of an access profile of the media data titles at the proxy.

59. The method of claim 51, further comprising causing the central server computer system to transmit data in the media data titles to the proxy server computer system via a backbone network connection, and the proxy server computer system to transmit data in the media data titles to one or more client(s) via a local network connection;

wherein a peak transmission rate in the backbone network connection for the central server computer system to transmit data in the media data titles to the proxy server computer system is reduced.

62. The method of claim 51, said sub-blocks of said at least one media data title cached at said proxy server computer system comprise partial information of substantially, all of the video frames in said at least one media data title.

63. A method of caching in a system for transmitting a plurality of media data titles to one or more client(s) from a central server computer system and a proxy server computer system located in a computer network, said proxy server computer system located in the network between the central server computer system and the one or more client(s), wherein each media data title is divided into blocks each divided into sub-blocks comprising partial information of video frames, wherein the video frames are to be sequentially transmitted to the one or more client(s), comprising:

causing the central server computer system to transmit data in the media data titles to the proxy server computer system via a backbone network connection, and the proxy server computer system to transmit data in the media data titles to one or more client(s) via a local network connection;

identifying which sub-blocks from different blocks of each media data title that are to be cached, wherein the identified sub-blocks include some sub-blocks in each of the blocks of at least one media data title;

caching only the identified sub-blocks at the proxy server computer system to reduce the transmission bit rate of the central server computer system in the backbone network connection for transmitting data in the at least one media data title to the proxy server computer system; and

transmitting sub-blocks of the media data titles cached at the proxy server computer system to the one or more client(s);

wherein the cached sub-blocks comprise partial video frames obtained at a set of sampling times and at a first sampling rate lower than that of a video source from which said information originates, said method further comprising combining the cached sub-blocks at the lower first sampling rate from the proxy server computer system with complementary uncached sub-blocks of such video frames taken at sampling times different from the set of sampling times of such video frames from the central server computer system into video data at a sampling rate higher than the first sampling rate and sending the video data at the higher sampling rate to the client(s).

64. The method of claim 63, wherein said blocks comprise video frames, and the sub-blocks comprise video information along some scan lines of the video frames so that the transmitting transmits some scan lines of the video frames.

65. The method of claim 63, wherein said transmitting transmits some scan lines that are evenly spaced across the video frames.

66. The method of claim 63, said sub-blocks of said at least one media data title cached at said proxy server computer system comprise partial information of substantially all of the video frames in said at least one media data title.