Transmission and reception of audio and/or video material

• US 20040064573A1
• Filed: 06/02/2003
• Published: 04/01/2004
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Leaning, Anthony R, Whiting, Richard J
• Granted Patent: US 7,447,791 B2
• Time in Patent Office: Days
• US Class Current: 709/231
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/1106 Call signalling protocols; H.323 and related
• CPC Class Codes: H04L 65/612 for unicast
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04L 67/06 specially adapted for file transfer, e.g. file transfer protocol [FTP]
• CPC Class Codes: H04L 67/60 Scheduling or organising the servicing of application requests, e.g. requests for application data transmissions using the analysis and optimisation of the required network resources admission control or resource allocation H04L47/70
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/234327 by decomposing into layers, e.g. base layer and one or more enhancement layers
• CPC Class Codes: H04N 21/234354 by altering signal-to-noise ratio parameters, e.g. requantization
• CPC Class Codes: H04N 21/23439 for generating different versions
• CPC Class Codes: H04N 21/25808 Management of client data terminal profiles in network data switching protocols H04L67/303
• CPC Class Codes: H04N 21/2662 Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]
• CPC Class Codes: H04N 21/4392 involving audio buffer management
• CPC Class Codes: H04N 21/44016 involving splicing one content stream with another content stream, e.g. for substituting a video clip
• CPC Class Codes: H04N 21/440227 by decomposing into layers, e.g. base layer and one or more enhancement layers
• CPC Class Codes: H04N 21/44209 Monitoring of downstream path of the transmission network originating from a server, e.g. bandwidth variations of a wireless network arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896
• CPC Class Codes: H04N 21/472 End-user interface for requesting content, additional data or services; End-user interface for interacting with content, e.g. for content reservation or setting reminders, for requesting event notification, for manipulating displayed content end-user interfaces for retrieving video data from a database G06F16/739; network services for supporting unicast streaming H04L65/612
• CPC Class Codes: H04N 21/6373 : for rate control , e.g. request to the server to modify its transmission rate flow control in packet networks H04L47/10
• CPC Class Codes: H04N 21/6377 : directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/658 : Transmission by the client directed to the server
• CPC Class Codes: H04N 21/8106 : involving special audio data, e.g. different tracks for different languages
• CPC Class Codes: H04N 21/845 : Structuring of content, e.g. decomposing content into time segments

Abstract

Delivery of recorded audio or video material over a telecommunications link 2 from a server 1 to a terminal 3 is accomplished by dividing the material into a sequence of sub-files each of which is independently requested by the terminal, which thereby has control of the rate of delivery. Provision may be made for switching between alternative sub-file sets representing alternative delivery modes or data rates.

Claims

1. A terminal for playing audio or video material which is stored on a remote server as a set of files representing successive temporal portions of the said material, the terminal comprising:

a telecommunications interface for communication with the server;

a buffer for receiving the files from the telecommunications interface; and

means for playing the contents of the buffer;

characterised by control means operable to determine the addresses of further files to be requested and operable in response to the state of the buffer to generate request messages, containing such addresses, for further files for replenishment of the buffer.

2. A terminal according to claim 1 arranged in operation to decode the files before storing them in the buffer.

3. A terminal according to claim 1 or 2 including means operable to generate a series of trial requests to identify the most recent file and to commence decoding starting with the identified sub-file.

4. A terminal according to claim 1, 2 or 3 for use with a server storing a plurality of sets of files, which sets correspond to respective different delivery modes, the terminal including:

means operable to effect mode switching by providing that subsequent request messages shall request files from a set different from the set to which the immediately preceding request related.

5. A terminal according to claim 4 for use with a server in which at least some of said sets of files correspond to respective different data rates, in which:

the terminal includes means for monitoring the received data rate;

the mode switching means is operable, in the event that the measured rate is below that needed for the set to which the currently requested file belongs, to provide that subsequent said request messages shall request files from a set corresponding to a lower data rate.

6. A terminal according to claim 4 or 5 for use with a server in which at least some of said sets of files correspond to respective different data rates, in which:

the terminal includes means for monitoring the received data rate;

the mode switching means is operable, in the event that the measured rate is sufficient to support delivery of files of a higher data rate than that of the set to which the currently requested file belongs, to provide that subsequent said request messages shall request files from a set corresponding to a higher data rate.

7. A terminal according to claim 4, 5 or 6 for use with a server in which at least some of said sets of files correspond to respective different playing modes, in which:

the terminal includes means to receive commands from a user of the terminal to perform said mode switching from a current playing mode to a desired playing mode corresponding to that command; and

the mode switching means is operable, upon receipt of the command, to provide that subsequent said request messages shall request files from a set corresponding to said desired playing mode.

8. A terminal according to any one of claims 1 to 7 for use in a method according to any one of claims 19 to 22, in which the terminal is operable upon receipt of a file to decode it and to discard that part of the decoded material which corresponds to said initial part of the following portion.

9. A terminal according to any one of claims 4 to 7 for use with a server storing said material in the form of video recordings, at least some of said files having been encoded using, for at least some frames thereof, inter-frame coding, in which the terminal is arranged in operation, before generating the request message for a file from a different set, to generate a request message for a file for correction of decoder tracking.

10. A terminal according to any one of the preceding claims in which the files are allocated addresses according to a predetermined algorithm and the terminal includes means operable for a said request message to calculate, in accordance with said algorithm, an address for inclusion in the request message.

11. A method of transmitting digitally coded audio or video material comprising:

partitioning the material into a plurality of discrete files each representing successive temporal portions of the said material;

storing the files at a first station; and

at a second station—

a) transmitting to the first station requests for successive respective ones of the files;

b) receiving the files; and

c) decoding the files for replay of the material.

12. A method according to claim 11 in which the material is stored in a buffer and the request messages are generated in dependence on the state of the buffer.

13. A method according to claim 12 in which the material is stored in the buffer after decoding.

14. A method according to claim 11, 12 or 13, including, at the second station, generating a trial request for a first file, receiving from the first station a reply including data representing the original time of the first file and the time of said reply, and estimating from these data an estimated identity of the most recent file at the first station.

15. A method according to claim 11, 12, 13 or 14 including generating, at the second station, a series of trial requests to identify the most recent file at the first station and commencing said decoding starting with the identified file.

16. A method according to any one of claims 11 to 15 including storing a plurality of sets of files, which sets correspond to respective different delivery modes, and including, at the second station, effecting mode switching by providing that subsequent request messages shall request files from a set different from the set to which the immediately preceding request related.

17. A method according to claim 16 in which at least some of said sets of files correspond to respective different data rates, including:

monitoring the received data rate at the second station; and

in the event that the measured rate is below that needed for the set to which the currently requested field belongs, performing mode switching to provide that subsequent said request messages shall request files from a set corresponding to a lower data rate.

18. A method according to claim 16 or 17 in which at least some of said sets of files correspond to respective different data rates, including:

monitoring the received data rate at the second station; and

in the event that the measured rate is sufficient to support delivery of files of a higher data rate than that of the set to which the currently requested file belongs, performing mode switching to provide that subsequent said request messages shall request files from a set corresponding to a higher data rate.

19. A method according to claim 16, 17 or 18 in which at least some of said sets of files correspond to respective different playing modes, in which:

the second station includes means to receive commands from a user of the second station to perform said mode switching from a current playing mode to a desired playing mode corresponding to that command; and

the mode switching means is operable, upon receipt of the command, to provide that subsequent said request messages shall request files from a set corresponding to said desired playing mode.

20. A method according to any one of claims 11 to 19 in which said material is audio material, in which:

a) the files are encoded using an audio coding method having a frame structure;

b) the step of partitioning the material into a plurality of discrete files comprises notionally dividing the material into a plurality of temporal portions and generating each said file, other than the last, by coding one respective temporal portion and an initial part of the following portion such that the portions together represent a whole number of frames;

c) after decoding, that part of the decoded material which corresponds to said initial part of the following portion is discarded.

21. A method according to any one of claims 11 to 19 in which said material is audio material, in which:

a) the files are encoded using an audio coding method having a frame structure;

b) the step of partitioning the material into a plurality of discrete files comprises notionally dividing the material into a plurality of temporal portions and generating at least some of said files by coding one respective temporal portion and so much of the end of the immediately preceding temporal portion and/or the beginning of the immediately following temporal portion as to constitute with said one respective said temporal portion, a whole number of frames of said frame structure; and

c) after decoding, that part of the decoded material which corresponds to said end of the immediately preceding temporal portion and/or beginning of the immediately following temporal portion is discarded.

22. A method according to claim 20 or 21 in which said sets comprise a first set and a second set for which the frame length is different from that used for encoding the second set, and the division into temporal portions is the same for both sets.

23. A method according to claim 20, 21 or 22 when dependent on claim 13 in which that part of the decoded material which corresponds to said initial part of the following portion is not stored in the buffer.

24. A method according to claim 16 or any one of claims 17 to 23 when dependent on claim 16 in which said material is in the form of video recordings, at least some of said files having been encoded using, for at least some frames thereof, inter-frame coding, and including, at the second station, before generating the request message for a file from a different set, generating a request message for a file for correction of decoder tracking.

25. A method according to any one of claims 11 to 24 in which the files are allocated addresses according to a predetermined algorithm, the method including calculating, at the second station in accordance with said algorithm, an address for inclusion in a request message.

26. A method according to claim 25 in which the algorithm generates the addresses in accordance with a key, including the step of transmitting the key to the second station for use in calculating the addresses.

27. A method according to claim 26 in which the algorithm generates the addresses in accordance with a pseudo-random sequence.

28. A method according to claim 27 in which the algorithm generates the addresses in accordance with a pseudo-random sequence and the key is a seed value for setting the start point of the pseudo-random sequence.

29. A method according to any one of claims 11 to 28 including, at the second station, the steps of:

(a) receiving from the first station a list containing times and data defining actions to be performed at those times;

(b) computing a time, relative to the beginning of the material, represented by the current playing point;

(c) comparing the computed time with the times in the list and, in the event of a match generating a command containing the respective data for initiation of the action.

30. A method according to claim 29 in which the actions include the display of a subtitle.

31. A method according to claim 29 or 30 in which the actions include the display of an image.

32. A method according to claim 31 including transmitting to the first station a request for images identified by the said data, and storing the images at the second station until required for display.