British Telecommunications Public Limited Company

British Telecommunications Corporation

Michael Erling Nilsson

Stephen Clifford Appleby

Rory Stewart Turnbull

Ian Barry Crabtree

Yousif Humeida

David G Morrison

Patrick J Mulroy

Timothy Sean Stevens

Mohammed Ghanbari

Timothy Ralph Jebb

Paul Farrow

Matthew D Walker

Ian Parke

Roberto Alvarez Arevalo

Timothy Stevens

David O Beaumont

Ivan Roper

Richard J Jacobs

Brahim Allan

Yousif Humedia

Mohammed Granbari

Tomasz Lyko

Nicholas Race

Matthew Broadbent

Christopher Mark Reason

Matthew David Walker

Richard James Jacobs

Stephen Clifford Aplleby

Patrick Joseph Mulroy

Described is a method of media content delivery, where measurements of network delivery rates are used to determine at which bit rate to request each content segment. The aim is to ensure continuous play-out of good quality segments, without relying on a large buffer, so that end-to-end delay is kept low. The historical network delivery rate is measured on two or more timescales, such as a short-term delivery rate and a long-term delivery rate, and these are used to decide when to request a higher bit rate segment than the previous segment, and when to request a lower bit rate segment than the previous segment.

Adaptive bit rate streaming

The invention provides a method of media content delivery, where the time taken to deliver each chunk of content is measured, from which the stability or consistency of delivery times are calculated. The amount of data buffered at the user's device awaiting decoding and play-back can then be adjusted (such as by playing out the content slower or quicker), in order to achieve a good compromise between continuous play-out and low end-to-end delay, taking into consideration the current network characteristics.

Low latency content delivery

A method of delivering a video sequence in a network, the sequence including a plurality of temporal segments encoded at a plurality of qualities, the method including storing a dataset indicating the relative size of segments of the video stream; computing in dependence on that dataset a time schedule for delivery of the segments, the time schedule indicating a target delivery time for each segment sufficient to deliver all the segments in the sequence in time for decoding and being independent of the encoded quality of each segment; for each segment: setting one or more transmission parameters for the segment in dependence on the target delivery time for the segment and the relative size of the segment; and delivering the segment over the network using the one or more transmission parameters.

Transmission parameter control for segment delivery

In examples of the present invention, during delivery of content, the round trip times for each delivered data packet are measured and the congestion window used for delivery is adjusted accordingly. The congestion window is set to a relatively high value when the round trip times are relatively low, and set to a relatively low value when the round trip times are relatively high.

Congestion response

Examples of the present invention provide a method of delivering media, such as a video sequence, to a client device from a server, taking into account the relative importance of different portions of the video sequence. The sequence is divided into temporal segments, with each segment encoded at a plurality of bitrates (and hence qualities). A viewer importance parameter is assigned to each segment, indicating the relative importance of that segment, with the information stored in a manifest file or similar. The client receives this segment and viewer importance data in a manifest file. As soon as the client is aware of a future segment marked as having higher viewer importance than the next segment for download, the client initiates the download of this further segment by making a request (e.g. HTTP request), while making a concurrent request for the delivery of the next segment.

Viewer importance adaptive bit rate delivery

A method of determining the bandwidth of a link carrying a plurality of data streams between a plurality of sources and a plurality of destinations in a network, the method including sending data packets from a first data stream over the link from one source to one destination at a first transmission rate, and measuring an associated first packet loss rate; sending further data packets from the first data stream over the link from the one source to the one destination at a second transmission rate, and measuring an associated second packet loss rate; and determining the bandwidth of the link in dependence on the first and second packet loss rates and the first and second transmission rates.

Determining the bandwidth of a communication link

A method of delivering media content over a network, the media content including a plurality of temporal segments, wherein each temporal segment comprises a plurality of data packets, the method including: selecting an initial size of a first congestion window; delivering the plurality of data packets of a first segment using the first congestion window, the initial size of the first congestion window being used to control the size of the first congestion window for the duration of the first segment delivery; measuring the packet loss during the delivery of the first segment; determining an initial size of a second congestion window in dependence on the measured packet loss for the first segment; and delivering a second segment using the second congestion window, the initial size of the second congestion window being used to control the size of the second congestion window for the duration of the second segment delivery.

Managing congestion response during content delivery

In examples of the present invention, delivery of a segment of content is done using an initial congestion window, preferably chosen to give a delivery rate that ensures timely delivery of that segment. However, under high levels of packet loss, the delivery rate may not be sufficient. Hence, at any stage during delivery of a segment, the actual delivery rate is measured, and used, together with the previous congestion window size, the amount of content segment data still to be delivered, and the time left for delivery, to calculate an updated congestion window. The remainder of the segment is then delivered using this revised congestion window.

Congestion response for timely media delivery

Described are methods of delivering media, such as a video sequence, to a client device from a server, taking into account the relative importance of different portions of the video sequence. The sequence is divided into temporal segments, with each segment encoded at a plurality of bitrates (and hence qualities). A viewer importance parameter is assigned to each segment, indicating the relative importance of that segment, with the information stored in a manifest file or similar. The client receives this segment and viewer importance data in a manifest file. The bit rate of each segment selected for download is dependent on the relative importance of that segment and future segments. The selected segment is then delivered to the client device from the server. Thus, segments having a higher viewer importance will be delivered with a higher encoded bitrate than segments having a lower viewer importance.

Examples of the present invention provide a method of converting a multicast stream into unicast segments. In particular, sequence identifiers are generated based on a clock reference field in the transport stream packets that make up the multicast stream. Every time a new sequence identifier is calculated, a new unicast segment is generated and assigned with the new sequence identifier. Transport stream packets are placed into the new segment until a packet is processed that causes a new sequence identifier to be generated, at which point another new segment is generated and packets placed into that segment. In an improved method, random access indicators in the transports stream packets are used to further constrain when a new segment is generated, to ensure that new segments are coincident with a packet having a random access indicator. This improvement makes random access easier back and forth between and within a stream.

Multicast to unicast conversion

The invention presents a method of providing feedback for receipt of a multicast video stream. The feedback mechanism allows the number of clients receiving over multicast to be determined, which can then be used to manage multicast delivery, including switching decisions between multicast and unicast. Video content is delivered over a multicast stream from a content server to a plurality of client devices. The client devices are each configured to respond at regular intervals whilst receiving the multicast video stream by transmitting an HTTP HEAD request message to the content server. The HTTP HEAD request refers to metadata relating to a manifest file associated with the video stream. The number of client devices receiving the multicast video stream is determined based on the number of HEAD requests received at the content server. The multicast video delivery can then be managed accordingly, and can also take into account the number of unicast clients that are requesting the corresponding unicast stream to the multicast stream.

Multicast streaming

Examples of the present invention present a method of controlling content delivery in a network. A global quality of experience measure, QoE, is calculated based on the packet loss rate in the network. As packet loss rate varies as a result of congestion conditions in the network, so will QoE. A server delivering content over the network will attempt to reach QoEfor the content in its respective session. Those sessions with a quality of experience, QoE, less than QoEwill have its packet dispatch rate increased, and those with a QoE higher than QoEwill reduce its packet dispatch rate, subject to any delivery deadlines associated with the session. If the delivery deadlines of the sessions can be met without exceeding QoE, then all sessions will end up achieving QoE. Since QoEis only a function of packet loss rate that all sessions miming over the same shared network agree upon, all sessions should converge on the same QoE.

Deadline driven content delivery

A method for providing equitable media streaming between an HTTP server and a number of receivers via shared network. The streaming data is processed to split the data across a number of sub-streams. Each sub-stream contains non-contiguous data. A receiver requesting the streaming media establishes a number of TCP sessions, one for each sub-stream and the received sub-stream data is reassembled at the receiver so that the streaming media can be presented.

Content delivery

A client device receives streamed encoded content data, such as encoded video data, which has been encoded at a constant perceptual quality. Several different versions of the content are available to be streamed to the device, at different perceptual quality levels. In order to decide which quality level to request from a content server at intervals the device calculates the delivery rates that would be required for each level of quality. The calculation of the delivery levels is made in dependence on whether the actual delivery rate that has been received so far is greater than or less than a constant bit rate delivery schedule that decreases monotonically but which guarantees to deliver the encoded data in a timely manner such that no buffer underflow and interruption of reproduction takes place. The monotonically decreasing bit rate schedule is defined by one or more 'critical points', which are the points at which the bit rates are decreased, and correspond to the points where the delivery schedule is just equal to the decoding schedule of the encoded data. At such points there would be no encoded data in a buffer at the client. If the delivery rate has been greater than the constant bit rate schedule for a quality then the delivery rate required going forward for a particular quality level can be calculated from the critical point information, and no more complicated calculation is required.

Growing community of inventors

Ipswich, United Kingdom

Michael Erling Nilsson