GB2469030A

GB2469030A - Buffering content to a predetermined threshold in an IPTV set top box

Info

Publication number: GB2469030A
Application number: GB0905403A
Authority: GB
Inventors: Christopher Lloyd; Craig Baxendale
Original assignee: MGT PLC
Current assignee: MGT PLC
Priority date: 2009-03-30
Filing date: 2009-03-30
Publication date: 2010-10-06
Also published as: GB0905403D0

Abstract

A set top box or other television device adapted to receive content over an Internet Protocol (IP) network connection; store the received content temporarily in a buffer until a pre-determined buffer fill threshold is reached and play out the received content when the threshold is reached whilst continuing to fill the buffer until play out is completed. For use in an IPTV set-top box.

Description

IPTV Set Top Box

Field of the Invention

The present invention relates to a method and apparatus for increasing IPTV Quality Of Service (Q0S) by minimising video or audio asset freezing while consuming (viewing or listening to) over a public internet using internet protocol television for video or audio on demand.

Background of the Invention

IPTV is defined as multimedia services such as television/video/audio/text/graph:cs/data delivered over IP based networks managed to provide the required level of quality of service and experience, security, interactivity and reliabiUty. IPTV is the delivery of a stream of content over a network using internet protocol, typically using a broadband connection. For residential users, IPTV is often provided in conjunction with video on demand (VOD). VOD systems stream video content to a user's set top box (STB) allowing viewing or download to a device for storage and viewing at any time. IPTV is typically supplied by a service provider using a closed network infrastructure rather than over the public internet.

IPTV live streaming and VOD services are becoming increasingly popular. However, service delivery can sometimes be of low quality. For example, the user may experience freezing of the video content whilst viewing.

Summary of the Invention

According to the present invention there is provided a set top box or other television device adapted to receive streamed content over an IP network connection, for example S.'... video content; store the received content temporarily in a buffer until a pre-determined buffer fill threshold is reached and play out the received content when the threshold is * reached whilst continuing to fill the buffer until play out or delivery of the content is completed. *.

By continuously adding data to the buffer after the threshold is reached and play out has started, fluctuations in the delivery of the content caused by, for example, fluctuations in * the broadband bandwidth, can be compensated for. This means that the quality of service delivery is improved.

The buffer may be configured to fill at a pre-determined rate that is a function of the video file bit rate. The function may be a multiple of the file bit rate, for example 2.5 times the bit rate.

During playback of the content, the buffer fills at a speed determined by the difference between the encoded bit rate of the content and the data delivery rate. The delivery rate will be the lower of the available network speed or maximum server delivery rate.

When play out of the content is paused, for example by the user, the buffer will continue to fill, although now it can do so at the full rate of the data delivery rate.

The system is operable to recognise when the buffer is emptying so rapidly that freezing or glitching will occur by actively monitoring the amount of buffered content available.

This can be done, for example, by defining a second buffer fill threshold below which service quality may be compromised.

When the system recognises that a problem is about to occur, it pauses the asset playing for a pre-determined time to allow the buffer to fill sufficiently that playback can continue without the risk of freezing. During this operation, the user is informed what is happening by means of an on-screen message. The system will override this buffering behaviour when it identifies that the buffer threshold has been breached near the end of playback of the content since it recognises that no further data is available to buffer.

During Fast Forward operations, the buffer will empty in proportion to the Fast Forward speed as the position in the asset moves through the associated position in the buffer.

When the Fast Forward operation takes the position in the asset beyond the point at * ***** * which it is contained in the buffer, the buffer will empty and only start to fill again once : *, the Fast Forward operation has ceased. S... * 30

Brief Description of the Drawings

*::::* Various aspects of the invention will now be described by way of example only and with reference to the accompanying drawings, of which: Figure 1 shows an IPTV STB advanced buffer system overview (with HIGH Watermark); Figure 2 shows ari PTV STB advanced buffer system overview (with LOW Watermark); Figure 3 shows the advanced buffer under Normal Video Playback; Figure 4 shows the advanced buffer under periods of reduced available bandwidth and Figure 5 shows the advanced buffer with pause during playback.

Detailed Description of the Drawinq

Figures 1 and 2 show a television system that has a display or screen for displaying content, such as video content, and an internet protocol television (IPTV) set top box (STB) that can be connected over the public internet via a broadband connection to, for example, a video streaming server and/or a content delivery network. This type of arrangement is well known in the art and so will not be described in detail.

Included in the STB is a buffer. This is a reserved area of storage, in memory or on a drive, where potential video content can be built up and stored ready for use under conditions of service interruption through, for example, extreme usage contention or reduction in service. The buffer size may be allocated, typically in multiples of bytes, from the internal STB memory (RAM); the internal SIB hard drive and an externally connected drive through a connection, such as a USB (not shown).

Defined within the buffer are two watermarks. The first sets the buffer fill level at which play out of a video starts. This will be referred to as the high watermark. The second is used to identify when quality of service may be compromised, for example when the buffer is emptying because contention is too great and glitching is about to start. The second watermark should be set at a level equal or less than the first to prevent their behaviours from interfering. This will be referred to as the low watermark. The maximum buffer size is the maximum capacity of the buffer.

The buffer may be configured to fill at a pre-determined rate that is a function of the * ** video file bit rate. The function may be a multiple of the file bit rate, for example 2.5 times the bit rate. During playback of the content, the buffer fills at a speed determined * by the difference between the encoded bit rate of the content and the data delivery rate.

The delivery rate will be the lower of the available network speed or maximum server **** delivery rate.

In use, an encoded video asset is streamed or requested using video on demand (VOD) to the IPTV STB over the public internet via a broadband connection for play out on the screen. This could be directly from the video streaming server or content delivery network. The first few seconds of an encoded file is delivered at the maximum rate the server can provide. The buffer in the SIB fills at the speed of the available broadband bandwidth until it reaches the first buffer watermark at which stage the video starts playing out, as shown in Figure 3.

After the first buffer watermark is reached, the buffer continues to flU at the incoming data rate (which is, in some cases, the maximum available bandwidth) minus the playing bit rate (because the video is using this quantity of data per second), while the video continues to play out, until the buffer is full. At this stage, the incoming rate is reduced to match the playing bit rate. This continues until the entire content has been received, at which stage there is no further incoming data available.

The buffer fills at the maximum rate the server can provide; limited only by the actual broadband speed of the consumer's internet connection. Various examples of the relationship between the encode rate of the received file, the broadband speed, the server delivery rate and the buffer fill rate are given below:

Example 1

File encode = 1.25 Mbps Actual broadband line speed 4 Mbps Maximum server data delivery rate= 3 Mbps Rate the buffer is being filled = 1.75Mbps (= Max Server rate -File encode) In this example, there will be an initial burst of data at the maximum rate the server can provide to fill the first, high watermark in order to start playing the asset as quickly as possible. This drops to 3 Mbps (as determined by the maximum server data delivery rate) -the buffer now fills at 1.75Mbps. Once the buffer is full, the data rate drops to the * : third and final value of the 1.25 Mbps -the file bit rate. S S.

Example 2 *..

* File encode 1.25 Mbps Actual broadband line speed = 8 Mbps S...

Maximum server data delivery rate = 2 Mbps Rate the buffer is being filled = 0.75 Mbps (= Max Server rate -File encode)

Example 3

File encode = 1.25 Mbps Actual broadband line speed = 8 Mbps Maximum server data delivery rate = 10 Mbps Rate the buffer is being filled = 6.75 Mbps ( Broadband line speed -File encode) Fluctuations in the broadband speed are a significant source of quality of service problems in the dehvery of VOD. Where available broadband speed exceeds the video file encode bit rate, the buffer fills as fast as the stream connection allows. If the actual broadband speed falls below the encoded size of the video asset, as shown in Figure 4, play out continues uninterrupted using the content in the buffer. This continues until the broadband speed is restored above the encoded size of the video asset or the buffer reaches the low watermark that indicates that freezing or glitching of the content is about to occur.

When the low watermark is reached the content playing is immediately paused, a suitable indication is presented to the user, and the buffer is allowed to fill sufficiently for smooth playback. However, the system is adapted to override this buffering behaviour when it identifies that the buffer threshold has been breached near the end of playback of the content since it recognises that no further data is available to buffer.

If the buffer is sufficiently large and it is filled to capacity during a period of high broadband speed availability then it could conceivably contain the entire asset and play out to completion even if the connection is completely lost.

The buffer arrangement can accommodate the use of user-controlled functions, such as pause, and fast forward. Figure 5 illustrates the situation where the video playing out is paused by a user. In this case, while the video is paused, the full amount of the incoming bandwidth is used to fill the buffer. When play out is resumed, the buffer fills at * ** S..

* the incoming data rate minus the playing bit rate, until the buffer is full. At this stage, the : .. incoming rate is reduced to match the playing bit rate. S... *. 30

In order to ensure streaming controls (Pause, FFD, RWD) are still available, a keep *::::* alive' connection is established with the streaming server until the completion of the video (buffer empty). If the buffer has only partially filled during high broadband speed availability and reduction in service is experienced below the encoded bit rate of the video asset, the amount of available asset will be reduced and the length of time it will continue to play out will be reduced.

The buffer can be configured as a single element of addressable memory or as a primary' and secondary' buffer, which fills during playback. The system manages the switch from the secondary buffer to the primary buffer when data is required. In this case, three attributes are set: low watermark (primary buffer value), high potential incoming data rate (a multiple of the file bit rate) and high secondary buffer.

If the buffer size is 6Mbytes and the encoded asset is 1.25Mbits/sec, then the time the buffer will run for is 6 * 8 (Mbits) I 1.25 = 38.4 seconds. Larger buffer availability means that more video asset will be available to play from the buffer during times of reduced broadband connection speed, e.g. if the buffer size is 64 Mbytes and the encoded asset is I.25Mbits/sec then 64 * 8 (Mbits) / 1.25 = 409.6 seconds = 6. minutes 49.2 seconds.

The present invention provides a simple and effective technique for minimising freezing during VOD and asset streaming. A watermark to be set for initial video play out and an SIB buffer to be set to a maximum size in excess of the bit rate of the encoded video asset and fill to capacity using available broadband speed.

A skilled person will appreciate that variations of the disclosed arrangements are possible without departing from the invention. For example, whilst the invention has been described primarily in the context of a video asset, it will be appreciated that any IP content can be delivered, for example audio/text/graphics/data. Also, it will be appreciated the the invention can be used for both Over the Top (OTT) and complete managed solutions (IPTV usually refers to the latter). Furthermore, although the buffer system of the. invention is described in the context of a SIB that is connected to a television, it could be implemented as an integral part of a television. Accordingly the above description of the specific embodiment is made by way of example only and not for the purposes of limitation. It will be clear to the skilled person that minor * ***** * modifications may be made without significant changes to the operation described. * ** * * * **** * S..

S * S *S55 S. ** * . . * S

Claims

Claims 1. A set top box or other television device adapted to receive content over an IP network connection; store the received content temporarily in a buffer until a pre-determined buffer fill threshold is reached and play out the received content when the threshold is reached whilst continuing to fill the buffer until play out is completed.
2. A set top box or other television device as claimed in claim I wherein the buffer is configured to fill at a pre-determined rate that is a function of the content bit rate.
3. A set top box or other television device as claimed in claim 2 wherein the function is a multiple of the file bit rate, for example 2.5 times the bit rate.
4. A set top box or other television device as claimed in any of the preceding claims wherein the buffer fills at a speed determined by the difference between the bit rate of the data stream and the speed of the link in the IP network.
5. A set top box or other television device as claimed in any of the preceding claims wherein the buffer continues to fill when the user pauses the content.
6. A set top box or other television device as claimed in any of the preceding claims adapted to recognise when emptying of the buffer compromises quality of the data delivery.
7. A set top box or other television device as claimed in claim 6 adapted to recognise when the buffer is emptying too quickly.* *.**. * *

: *.
8. A set top box or other television device as claimed in claim 6 or claim 7 adapted * 30 to monitor the amount of buffered content available.

**
9. A set top box or other television device as claimed in claim 8 adapted to monitor ** a second buffer fill threshold below which service quality may be compromised.
10. A set top box or other television device as claimed in any of claims 6 to 9 adapted to pause the data play out for a pre-determined time to allow the buffer to fill sufficiently that playback can continue without compromising quality of service.
11. A set top box or other television device as claimed in claim 10 adapted to inform a user of the pause in delivery.
12. A set top box or other television device as claimed in claim 11 adapted to inform a user of the pause by causing an on-screen message to be presented.
13. A set top box or other television device as claimed in any of the preceding claims wherein a fast forward facility is provided and the buffer empties in proportion to the fast forward speed.
14. A set top box or other television device as claimed in claim 13 wherein when the fast forward operation takes the position in the data beyond the point at which it is contained in the buffer, the buffer empties and only fills again when the fast forward operation has ceased. * ***S * I * I. *, I S... a *SS S...S S I, ** * I S * S