WO2008068733A2

WO2008068733A2 - Mobile network communication of content

Info

Publication number: WO2008068733A2
Application number: PCT/IE2007/000121
Authority: WO
Inventors: Michael Senn; Philbert De Zwart (Philippus Gijsbert); Klaas Wijbrans
Original assignee: Markport Ltd
Current assignee: Markport Ltd
Priority date: 2006-12-07
Filing date: 2007-12-06
Publication date: 2008-06-12
Anticipated expiration: 2009-06-07
Also published as: WO2008068733A3

Abstract

Imminent (or already exceeded) expiry of a licence to use content such as a ringback tone is communicated by deliberately playing (9) modified content, such as by decreasing the quality of the original content. Quality of the content is gradually reduced during a grace period after Texpiry (Fig. 1). The imminent expiry is communicated inherently in the content rather than in a separate notification, the content being modified (7) during the grace period in a manner to indicate imminent expiration. The automatic content modification has the effect of greatly reducing the number of content management messages transmitted in the network, reducing required bandwidth and network element processing operations. In audio content the player may remove frequency ranges by passing the content through a digital band pass filter.

Description

"Mobile Network Communication of Content"

INTRODUCTION

Field of the Invention

The invention relates to communication of content such as ring tones, ringback tones, and video clips or movies in communication networks such as mobile networks.

Prior Art Discussion

At present, such content is downloaded or otherwise made available to a user in response to payment of a periodic or one-time fee. Where the content has an expiry limit, based on time or number of uses, the use of the content is discontinued when the limit is reached. Typically a notification is sent to indicate this to the buyer/renter of the content.

The invention is directed towards providing for more versatile management of expiry of content validity as part of Digital Rights Management. Another object is to reduce the extent of messaging required for content management.

GLOSSARY

DSP Digital Signal Processor; microprocessor/coprocessor designed for performing the mathematics involved in Digital Signal Processing and specialised in processing (streamed) digital data e.g. information such as sound, video and images.

El A physical cable type used in signaling and voice communication within Telecom operators.

FPGA Field Programmable Gate Array; highly flexible semiconductor devices used for various applications, like DSPs.

G.711 ITU standard for audio compression. HSL, HSV, HSB Hue Saturation Brightness colour model describes perceptual colour relationships more accurately than RGB, while remaining computationally simple. HSL stands for hue, saturation, lightness, while HSV stands for hue, saturation, value and HSB stands for hue, saturation, brightness.

IMS IP Multimedia Subsystem, an architectural framework for delivery of internet protocol (IP) multimedia to mobile users.

IP Internet Protocol.

MMS Multimedia Messaging Service, a multimedia-capable messaging service similar to SMS.

MSC Mobile Switching Centre, the element in the network that performs switching between mobile and fixed or mobile network elements.

QoS Quality of service.

RGB Red, green, and blue pixel values.

RTP Real-time Transport Protocol, a standardized packet format for delivering audio and video over the internet where real-time transmission, is required.

SCP Signaling Control Point/Service Control Point, network element within a telecom environment handling part of the call control.

SMS Short Message Service, a service provided by mobile operators to send and receive short text based or binary data messages.

VoIP Voice over IP, .the bundling of several protocols to enable the transmission of voice telephony over Internet Protocols (IP).

WAP Wireless Application Protocol, set of protocols enabling applications to be accessible to and operable over wireless communication networks.

Sample A value or a set of values at a point in time and/or space, a large number of samples making up a complete item of content. SMIL Synchronized Multimedia Integration Language, a W3C-recommended

XML mark-up language for describing multimedia presentations.

SUMMARY OF THE INVENTION

According to the invention, there is provided a method for managing content in a communication network having subscriber devices, the method comprising the steps of:

storing content usage criteria including a validity limit for subscriber use of an item of original content;

monitoring usage of the. original content according to said content usage criteria to determine when the validity limit approaches or has passed; and

if the validity limit approaches or has passed playing modified content, said modified content inherently conveying information that the validity limit is approaching or has passed.

In one embodiment, the method comprises the step of dynamically modifying the original content in real time to provide the modified content to be played.

In one embodiment, a mixing process mixes the original content with modification .content in real time.

In one embodiment, the mixing process comprises initially determining an original content identifier and content usage data, subsequently retrieving the original content using said identifier, and performing the mixing according to the usage data.

In one embodiment, the mixing process implements the following steps to determine the extent of content modification required: if content is 'valid' no degradation is performed, if the content is 'in grace period': calculate usage as a percentage of maximum allowed grace usage modification Amount = ( 'content usage' / 'max grace period' ) * 100 if the content 'expired' or 'not found': play standard default content to caller.

In one embodiment, the mixing process implements the following steps to mix the original content with the modification content: origContent _{ + NoiseΛmount x Scratch_; 1 + NoiseAmount where, Oi is the played content, origContent is the original content,

NoiseAmount is the proportion of the original content to be modified, Scratch is the modification content that is used to modify the original content.

In one embodiment, the modified content is pre-modified, and is selected in real time.

In one embodiment, the original content is a ringback tone, and a player of the network plays a modified ringback tone to a caller.

In one embodiment, the modified ringback tone is played by a player on a network server.

In one embodiment, a tag or a content envelope is provided for the modified content, indicating on a standardised basis the extent or nature of content modification.

In one embodiment, the modified content is in an MMS message and the degree of modification is indicated in an SMIL wrapper, to be applied by an MMS client of the network.

In one embodiment, the method comprises the step of at least one intermediate communication network element routing the modified content and avoiding taking any QoS action because it automatically recognises the tag. In one embodiment, the content is a ring tone, and a subscriber device of the network plays the modified content.

In one embodiment, the method comprises the further step of a server downloading the original content to a subscriber device together with the content usage criteria, and the subscriber device performs the steps of monitoring said content usage and playing modified content.

In one embodiment, the content is modified by a dedicated hardware device.

In one embodiment, said device comprises a comparator for comparing a threshold level representing usage of the content with a randomly-generated number for every sample of original content, and a summing block for adding a sample of modification content to the original content sample if the threshold is exceeded.

In one embodiment, the original content is a ring tone and the dedicated device is on a subscriber device.

In one embodiment, the dedicated device is an FPGA.

In one embodiment, the method comprises the further step of determining a channel type and playing the modified content according to said channel type.

In one embodiment, the modified content is artificially aged, for example to make it sound like a damaged vinyl record if the content includes audio. The modified content may include artefacts such as noise, hum, rattle, scratches, spoken text, advertisements, or logos.

The original content may be modified by volume change, and/or by brightness change, and/or by contrast change, and/or by colour reduction. The modification may be implemented according to the following algorithm for R, G, and B pixels:

Rnew= (1 -NoiseAmount*R_old)+NoiseAmount*((R₀id+Goid+Boid)/3)

(1 -NoiseAmount*G₀id)+NoiseAmount*((Roid+G₀id+Boid)/3) B_new^ (l-NoiseAm.ount*B_old)+NoiseAmount*((R_old+G_old+B_old)/3) where NoiseAmount is the proportion of the original content to be modified.

In one embodiment, the original content is modified by colour shifts, and/or by audio frequency shifting or filtering, and/or by limiting its duration, and/or by reducing video frame rate, and/or by reducing audio sample rate, and/or by removing audible frequency ranges such as by passing it through a band-pass filter.

The original content may comprise wallpaper or other images, a game, music, a video clip, and/or a movie.

In one embodiment, the original content comprises multimedia content, consisting of two or more of the above, such as two or more of audio, image, video, and text.

According to another aspect, the invention provides a content server or group of servers comprising means for implementing the steps of any method as defined above.

In a further aspect, the invention provides a mobile device comprising means for performing the steps of any method defined above.

In another aspect, the invention provides a computer program product comprising software code for performing operations of any method defined above when executing on a digital processor.

DETAILED DESCRIPTION OF THE INVENTION

Brief Description of the Drawings The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a plot illustrating in general terms a mechanism of the invention for managing content,

Fig. 2 is a flow diagram illustrating a content management method of the invention implemented in a mobile network, in this embodiment with server- based content modification;

Fig. 3 is a message sequence diagram illustrating operation of a system of the invention, in which a mobile device implements content modification; and.

Fig. 4 is a diagram of an FPGA resident on a subscriber mobile device for implementation of content modification on a mobile device.

Description of the Embodiments

Overview

In the invention, imminent (or already exceeded) expiry of a licence to use content such as a ringback tone is communicated to the subscriber/user by deliberately playing modified content, such as by decreasing the quality. This is shown in Fig. 1, which illustrates that quality of the content is gradually reduced for a period after T_eXpi_ry. T_expii_y may be a conventional cut-off expiry time, or a different one. Alternatively expiration may be based on number of uses of the content item, or other expiration criteria may be applied. In this specification the terms a "content usage validity limit" and "content usage expiry" mean the start of the grace period either on a timed (age) basis or on the basis of number of uses, the above embodiment being time-based.

The imminent expiry is communicated inherently in the content rather than in a separate notification, the content being modified during the grace period in a manner to indicate imminent expiration. The automatic content modification has the effect of greatly reducing the number of content management messages (the traditional method of communicating imminent content expiry) transmitted in the network, reducing required bandwidth and network element processing operations.

The content modification may be done in a creative and pleasant way. For example, for audio content it may introduce artificial scratches, noise and hum normally heard on an original vinyl record after playing many times. The volume and frequency of these scratches, noise and hum is made dependent on the amount of time the content, such as ringback tone, is overdue. As a result of this degrading ringback tone, friends of the subscriber calling him will be inclined to make mention of this, thus triggering the subscriber to renew the ringback tone with either the same content or a new piece of content. For video content (e.g., video ringback content) even more modification options are possible in addition to the changes to the audio quality. The modification may for example remove colour, introduce static noise, reduce contrast or brightness, or add a specific colour hue.

Additionally, the subscriber owning the content may hear the same degraded ringback tone when asking for a preview of his current ringback tone via IVR, Web/WAP or dialling a special number, or in the case the operator also supports caller ringback tone for the originator (i.e., someone hears his own ringback tone when calling someone else).

Dynamic Modification of Ringback Tones

Referring to Fig. 2, a mobile network content management system implements steps 1 through 10 while communicating with a service control point (SCP) and with a mobile switching centre (MSC) of the mobile network. A player of the system is the main component controlling and performing the method. The content management system stores original content, in this case ringback tones; and modification content, in this case audio samples of different types of scratches and noise. In real-time when playing out the ringback tone, an original ringback tone is mixed with scratch/noise samples.

In more detail the steps are as follows: 1. A (audio or video) notification from the SCP of a call comes in, identifying the called party ID₅ the calling party ID, channel type, and channel ID.

2. A (audio or video) ringback tone selection process of the player checks a ringback tone database for the characteristics of the recipient.

3. The ringback tone database returns the ID of the (original) ringback tone content that should be played, along with its licence expiry status (valid, in grace period, or expired). This ID is a lookup identifier for accessing the content to be played in a ringback tone content storage accessed by the player.

4. The selection process invokes a mixing process of the player, communicating to the mixing process the ringback tone content ID, licence validity limit, the channel type, and the channel ID. The channel type specifies the transmission media, examples being a Voice Channel using an El trunk or a Video Channel over IP. The Channel ID is the specification of the reserved part of the channel. An example is when playing the content towards an El voice trunk, the El has available 31 distinct channels, coordination between the mixing service and the MSC is determined by the channel ID. In this way the MSC is able to join the call circuit to allow the ringback tone to be played and heard by the calling party. A channel type is used to specify what type of transmission media is used towards the calling party. In one example, there are two choices: legacy voice and Internet audio. In the case of a legacy voice network, it is recoded as G.711 and inserted in the El bearer time slot. In the case of Internet audio, it is recoded as the negotiated codec (which may be G.711) and inserted as a sample in the VoIP RTP packet. The channel type need not be restricted to these two examples; it may also be used when providing aging (modification which sounds like aging of a medium such as a vinyl record) on static content for messages using MMS, IMS or even SMS.

5. In parallel with step 4, the selection process notifies the SCP that the original ringback tone origContent (e.g. song) is found and streaming will commence. The notification is made following standard call-handling procedures to prevent the ordinary network tone from being generated. If the ringback tone has not been found a default tone will be played.

6. The mixing process retrieves the original ringback tone from the ringback tone content store using the ringback tone's content ID. Optionally the channel type may be used to retrieve the appropriate content quality or format, for example G.711 when playing out to a voice channel over an El trunk.

7. The mixing process calculates an appropriate level of modification to be achieved by mixing in of noise/scratches based on the usage of the content. An example rule set is:

If content is 'valid' no degradation is performed.

If the content is 'in grace period'

Calculate age as percentage of maximum allowed grace period Noise Amount = ( 'content age' / 'max grace period' ) * 100

If the content 'expired' or 'not found'

Play standard default content to caller.

8. Fetch the samples for the 'Noise Amount' required, from the modification content storage.

Using the channel type and channel ID passed by the ringback tone selection process, the mix of original ringback tone and noise/scratches is played to the calling party. For each original content sample (1 Byte, in the example of G.711 encoding), the player mixes the incoming original content sample and the noise sample using the standard procedure of adding the samples and

,. . , , _Λ origContent. + NoiseAmount x Scratch. normalizing the volume O₁ = — - .

1 + NoiseAmount where Oi is the returned sample after normalising the volume, origContent is the original content,

NoiseAmount is the proportion of the ringback to be degraded, in this case by adding a fixed proportion to every sample, Scratch is the content sample that is used to degrade the playback to the calling party.

If a problem arises in the mixing operation then by default the player plays the original content. The step 9 allows utilisation of the relevant playout channel type, depending on factors such as the required resolution for example.

10. The mixed audio samples are streamed onto the channel towards the MSC in the right format.

The client device of the calling party (Internet VoIP, ISDN or mobile network) or the local exchange and the speaker on the client phone (analog PSTN lines) converts the incoming played content stream to an audible, analog audio signal. Because of the fact that the played audio signal includes the mixed noise, the calling party is made aware of the expiration or near expiration of the ringback tone and may make a remark on it to the called party. The subscriber will then be able to repurchase the content or change to another or default tone.

Selection of Pre-modified Content

In an alternative embodiment, instead of dynamically mixing original content with modification content, a base set of content files each with a certain percentage of degradation are created and stored within a content store. The method performs a calculation to determine the required degradation and then dynamically selects the pre-generated file at that level. This would be beneficial particularly where dynamic modification would affect network performance in terms of jitter or delay for example, or where a limited number of modification granularity levels are required.

Where modified content is selected rather than being dynamically generated, offline mixing may take place in the background and the player automatically selects a degraded variant of the content based on the amount of time or number of uses it is overdue.

Modification of Ring Tone Content Apart from ringback tones,, the invention also can be used for the indication of content expiry for other types of content such as ring tones. In the case of a ring tone implementation, a ring tone is first downloaded to the mobile device as indicated in Fig 3. In this embodiment WAP and SMS are given as bearer examples, but other bearers such as MMS are equally applicable. Part of the download is not only the ring tone, but also the validity period of that ring tone. The ring tone then is used by the device until the validity period has expired. After that, the ring tone is modified, namely aged, by mixing in noise or pre-recorded samples. The invention thus enables the transmission of content with validity limit to another entity for playing of the content.

Referring to Fig. 4, the mobile device may have dedicated hardware such as an FPGA as shown. The FPGA has a DSP core with comparator, multiply, and sum components. It also has a sample store, a device for generating random numbers (e.g., a physical component generating noise) and a D/A converter.

The audio information passes through the DSP. At each sample of 1 Byte, (G.711 encoding) a random number is generated from the random number generator and . compared to a threshold which is proportional to amount of grace period utilised. If the number is below the threshold, the audio data is mixed with a sample from the sample store. If the number exceeds the threshold, the original audio data is passed

■ through. The amount of distortion introduced is thereby also proportional to the amount of grace period utilised of the original content. An example is:

The content maximum grace period is 10 days, The specific content is 3 days into the grace period. Using the following calculation Threshold will be 30

Threshold = ('grace period daysY'max grace period') * 100 As each sample is processed a random number between 0 and 100 is generated and compared to the Threshold. In this example there is a 30% chance that the generated number is less than the Threshold and therefore the content will be degraded by 30%. If the content is O days into the grace period then there is 0% chance that a number will be lower than the Threshold (0).

Such an implementation allows a low-power, low-cost implementation on devices. The use of the random number generator ensures that the distortion will be different each time.

Tagging of Modified Content

A network element or server may tag the content to indicate that it has been modified. This tagging would be recognised by a content monitoring system such as a QoS system, and so false alarms concerning the content quality can be avoided. Also advantageously such tagging can pre-empt a quality monitoring system taking corrective action which might diminish or negate the effect of the content modification, for example if the modification resulted in reduced volume then a network system that might otherwise introduce automatic volume gain control would know not to do so based on such tagging. At a lower level of detail, the tagging may be performed using QoS Packet Tagging (IEEE 802. Iq tagging) or within messaging headers for example SMIL in the case of MMS.

Advantages of the Invention

It will be appreciated that the invention achieves much reduced messaging for communication of content management information. The invention advantageously avoids need to send out such notifications for the individual content items which have reached or are about to reach their validity limit (start of grace period). For example, compared to a conventional implementation with 3,000,000 subscribers, two warning notifications per expiry, two SMS messages per notification and an average validity period of two (30-day) months, the invention saves 200,000 SMS messages per day.

It also will be appreciated that content management systems sending out notifications typically do so during scheduled intervals only, which may often be at off-peak time, whereas advantageously the invention allows the communication of content management information in real time.

Instead of receiving a single notification message (which can easily be ignored) or a large number of notification messages (which is highly irritating and may cause the customer to never buy a ring tone again), he is continuously reminded in a friendly and humorous way each time the content is used.

Content modification of the invention does not require much management overhead, unlike prior art which requires extra network resources to inform that the subscription is about to terminate/has terminated/prompts to get them to renew same, all of which can be expensive in terms of for example network signalling/resources if for example done via SMS.

Alternatives

The invention is not limited to the embodiments described but may be varied in construction and detail. For example, the content communication method of the invention may be implemented by a network other than a mobile network. Examples are TV broadcast systems, Internet service providers, or fixed telephone service providers or any other Digital Rights Managed type of content with an expiration, such as:

- Ring tones

- Wall papers and other general imagery - Games (e.g., reduce the frame rate or the maximum reaction speed in an interactive gaming environment)

- Video on Demand

- Full-download audio Content via the Internet or other communication channels (e.g. iTunes type services) - YouTube™-type services

- Video Clips - Multi-media, combinations of different types of media (For example MMS which can include combinations of media such as audio, image, video, text etc.)

- SMIL-based multimedia content.

In the case of video ringback tones and movies the content modification options are even more extensive, as not only the audio channel but also the video channel can be adapted. This would for example enable the deterioration to a 50 's style TV format by removing colour, introducing old cinema style flickering, old style television Moire patterns and any other appropriate creative transformation. Even still images could be deteriorated this way.

Where the original content is not merely audio, a variation of the algorithm used for Fig. 2 step 9 may be used, in which: Oi is the played content, origContent is the original content,

NoiseAmount is the proportion of the original content to be modified, Scratch is the modification content that is used to modify the original content. Thus, the mixing algorithm specified is not only applicable to audio information but equally can be used to add (visual) noise to image information (by applying the algorithm to the RGB values of selected pixels) or video information (by applying the algorithm to the RGB values of pixels in the sequence of video images). Also, it will be appreciated that alternative mixing processes can be used. The description above includes a process in which a chosen proportion is added to every sample, and an example (FPGA) in which modification content is only added to some of the samples. It is also possible that, whichever sample-level mixing technique is used, a certain portion of the original content may be excluded from modification. ^•

An alternative approach to content degradation is for example the degradation of content by removing specific frequency ranges. For example, where the original content has an audio frequency range of 20Hz-20kHz, it can be aged artificially by using a band-pass filter with a lower frequency and a higher frequency determined by the amount the content is over the content validity period. The frequency range of the content thus is reduced artificially to for example 300Hz-3kHz using a digital implementation of for example a Butterworth or Chebyshev bandpass filter where the coefficients are adapted with the amount the content is over the content validity period.

In an alternative embodiment, a subscriber may have subscribed to a cartoon service to receive a daily cartoon on his mobile phone. When the validity period of his subscription ends, the invention applies artificial aging to the cartoon image based on the amount of grace period already expired. An embodiment of this algorithm is the reduction of color information by applying the following formula to each pixel RGB value: Rnew⁼ (1 -NoiseAmount*R_old)+NoiseAmount*((R_old.+Goid+Boid)/3) G_new ⁼ (l-NoiseAmount*G_old)+NoiseAmount*((R_old+G_old+Boid)/3) B_new= (1 -NoiseAmount*B_oi_d)+NoiseAmount*((R_old+G_oi_d+B_old)/3) where NoiseAmount is the proportion of the original content to be modified. As a result of this, the image will fade to gray shades only when it becomes older, indicating with each cartoon sent to the subscriber that his subscription has expired.

A variation of this technique is to perform colour shifting by translating the RGB values to HSB values, shifting the_. H component in proportion to the amount of grace period already expired, optionally reducing the S component in proportion to the amount of grace period already expired, and then translating back to RGB values as specified in ht1p://en.wildpedia.org/wiki/HSV_colour_space.

The content storage can be any facility that accepts a unique identifier and is able to efficiently return the content relating to the specific identifier. In general, it will be appreciated that other techniques for content modification could be used, such as those known in the image processing field.

Claims

1. . A method for managing content in a communication network having subscriber devices, the method comprising the steps of:

monitoring usage of the original content according to said content usage criteria to determine when the validity limit approaches or has passed; and

2. A method as claimed in claim 1, comprising the step of dynamically modifying the original content in real time to provide the modified content to be played.

3. A method as claimed in claim 2, wherein a mixing process mixes the original content with modification content in real time.

4. A method as claimed in claim 3, wherein the mixing process comprises initially determining an original content identifier and content usage data, subsequently retrieving the original content using said identifier, and performing the mixing according to the usage data. A method as claimed in either of claims 3 or 4, wherein the mixing process implements the following steps to determine the extent of content modification required:

if content is 'valid' no degradation is performed, if the content is 'in grace period': calculate usage as a percentage of maximum allowed grace usage modification Amount = ( 'content usage' / 'max grace period' ) * 100 if the content 'expired' or 'not found': play standard default content to caller.

A method as claimed in any of claims 3 to 5, wherein the mixing process implements the following steps to mix the original content with the modification content: origContent_i + NoiseAmount x Scratch_;

O₁ =

1 + NoiseAmount where, Oi is the played content, origContent is the original content,

A method as claimed in claim 1, wherein the modified content is pre-modified, and is selected in real time.

A method as claimed in any preceding claim, wherein the original content is a ringback tone, and a player of the network plays a modified ringback tone to a caller.

A method as claimed in claim 8, wherein the modified ringback tone is played by a player on a network server.

10. A method as claimed in any preceding claim, wherein a tag or a content envelope is provided for the modified content, indicating on a standardised basis the extent or nature of content modification.

11. A method. as claimed in claim 10, wherein the modified content is in an MMS message and the degree of modification is indicated in an SMIL wrapper, to be applied by an MMS client of the network.

12. A method as claimed in either of claims 10 or 11, comprising the step of at least one intermediate communication network element routing the modified content and avoiding taking any QoS action because it automatically recognises the tag.

13. A method as claimed in any of claims 1 to 7, wherein the content is a ring tone, and a subscriber device of the network plays the modified content;

14. A method as claimed in any preceding claim, comprising the further step of a server downloading the original content to a subscriber device together with the content usage criteria, and the subscriber device performs the steps of monitoring said content usage and playing modified content.

15. A method as claimed in any preceding claim, wherein the content is modified by a dedicated hardware device.

16. A method as claimed in claim 15, wherein said device comprises a comparator for comparing a threshold level representing usage of the content with a randomly-generated number for every sample of original content, and a summing block for adding . a sample of modification content to the original content sample if the threshold is exceeded.

17. A method as claimed in claim 16, wherein the original content is a ring tone and the dedicated device is on a subscriber device.

18. A method as claimed in claim 17, wherein the dedicated device is an FPGA.

19. A method as claimed in any preceding claim, comprising the further step of determining a channel type and playing the modified content according to said channel type.

20. A method as claimed in any preceding claim, wherein the modified content is artificially aged.

21. A method as claimed in any preceding claim, wherein the modified content includes artefacts such as noise, hum, rattle, scratches, spoken text, advertisements, or logos.

22. A method as claimed in any preceding claim, wherein the original content is modified by volume change.

23. A method as claimed in any ^"preceding claim, wherein the original content is modified by brightness change.

24. A method as claimed in any preceding claim, wherein the original content is modified by contrast change.

25. A method as claimed in any preceding claim, wherein the original content is modified by colour reduction.

26. A method as claimed in any of claims 23 to 25, wherein the modification is implemented according to the following algorithm for R, G, and B pixels:

G_new= (l-NoiseAmount*Go₁d)+NoiseAmount*((R_old+G₀id+Boid)/3)

(1 -NoiseAmount*B_old)+NoiseAmount^:I:((R_oi_d+G_o1d+B₀i_d)/3) where NoiseAmount is the proportion of the original content to be modified.

27. A method as claimed in any preceding claim, wherein the original content is modified by colour shifts.

28. A method as claimed in any preceding claim, wherein the original content is modified by audio frequency shifting or filtering.

29. A method as claimed in any preceding claim, wherein the original content is modified by limiting its duration.

30. A method as claimed in any preceding claim, wherein the original content is modified by reducing video frame rate.

31. A method as claimed in any preceding claim, wherein the original content is modified by reducing audio sample rate.

32. A method as claimed in any preceding claim, wherein the original content is modified by removing audible frequency ranges.

33. A method as claimed in claim 32, wherein the original content is modified by passing it through a band-pass filter.

34. A method as claimed in any preceding claim, wherein the original content comprises wallpaper or other images.

35. A method as claimed in any of claims 1 to 33, wherein Hie original content comprises a game.

36. A method as claimed in any of claims 1 to 33, wherein the original content comprises music.

37. A method as claimed in any of claims 1 to 33, wherein the original content comprises a video clip.

38. A method as claimed in any of claims 1 to 33, wherein the original content comprises a movie.

39. A method as claimed in any preceding claim, wherein the original content comprises multimedia content, consisting of two or more of audio, image, video, and text.

40. A content server or group of servers comprising means for implementing the steps of a method of any preceding claim.

41. A mobile device comprising means for performing the steps of the method of any of claims 1 to 39.

42. A computer program product comprising software code for performing operations of a method of any of claims 1 to 39 when executing on a digital processor.