Videonet - news, blogs and analysis for the pay-tv industry

• 21-Oct-2009 by Philip Hunter
• Adaptive Rate Streaming adds consistency to web TV
• IP Television

The recent Ukraine v England football match raised awareness of the Internet video quality issue even if it proved a disappointing sporting spectacle for away fans who paid £5 for the privilege. The event was streamed exclusively by Perform, which wisely restricted viewing to the first 1 million subscribers in order to avoid overloading the UK’s Internet infrastructure. Fortunately perhaps only about half the allocation was taken up, but this still represented the UK’s largest live sports streaming audience, and put some ISP backhaul networks under strain, leaving some viewers disappointed by the quality.

Nevertheless Perform has done a good job overcoming one Internet video quality issue, the latency involved when streaming over long distances between continents. This leaves the other big issue, which is the impact of multi-hop distribution over a shared Internet infrastructure that allocates bandwidth on a best effort basis, often inefficiently. Even if your own ISP supposedly delivers a healthy 8 Mbps of access bandwidth, you will rarely if ever be able to stream video at anything near that rate at present.

So even though Internet video quality has been improving, it is still inconsistent and unfit for delivering paid for services, except for once off sporting events where consumers have no choice. Varying bandwidth still often leads to delay starting streaming, along with stuttering playback, freezing frames, and unpleasant audio artefacts.

But there is promise of a substantial leap forward in Internet video quality over the next year, even without any spurt of network infrastructure construction. There is growing momentum behind the Adaptive Streaming Protocol (ASP), which looks like providing a standard way of optimising video transmission within the web environment.

ASP is based on the premise that most video transmission techniques fail to make good use of the aggregate capacity available within the web. ASP pumps content out from servers in parallel streams, each at different bit rates and formats, catering for varying network conditions and client abilities. Each parallel stream is in turn segmented into logical chunks with synchronised start and end times, each of which can take different paths through the network. At the receiving end, client devices then request the appropriate chunks of content to reassemble the best stream they are capable of receiving according to available bandwidth and display capability. The advantage of this is that the client is in charge of events, responding itself to changing network conditions rather than finding out about a sudden drop in bandwidth only when it is too late to prevent artefacts such as buffering delays.

This approach based on smaller chunks allows the distributed nature of the web to be exploited, making best use of the capacity available. It turns a weakness into a strength, rather like MIMO does for wireless transmission by transmitting data over different radio paths and reconstructing it at the receiving devices.

There are other advantages too, following from the use of the Internet HTTP protocol as the underlying transport mechanism.  Firstly many content delivery networks have already chosen HTTP for their infrastructure and so can deploy ARS more cheaply, without incurring the extra cost of supporting protocols such as RTSP (Real Time Streaming Protocol) and RTMP (Real Time Streaming Protocol) that on the face of it better optimised for real time data like video. The point here is that ASP on top of HTTP does the same job. In fact ASP does a better job when bandwidth is fluctuating during the course of a viewing session, as it often does over the Internet and particularly mobile connections, according to Bob Kulakowski, CTO of Verimatrix, which has adopted ASP alongside its VCAS content access system.

“While RTSP and RTMP have the same ability to sample the available bandwidth at the start of a streaming session and make choices of bitrates at that time, these are non- adaptive protocols and typically cannot change rates in a dynamic fashion as the quality of a delivery network fluctuates during a session,” said Kulakowski “You have to remember that the mobile delivery channel, for example, may fluctuate wildly even when moving around a home WiFi setup - and when you leave the home should be capable of switching to the use of 3G networks without hiccup. If the streaming approach does not deal with such issues, the typical consumer experience is unfortunately prone to rebuffering, stuttering playback, audio squawking etc., which are hard to tolerate from a user’s point of view.”

Furthermore, again by virtue of HTTP being ubiquitous across the Internet, ASP is well placed to reach all devices capable of receiving OTT content, Kulakowski added. “HTTP protocols are transparently able to traverse firewalls and broadband routers, extending the in-home video delivery network beyond the STB to PCs and other CE devices,” he said. As Kulakowski also pointed out, this tends to favour IPTV operators, given their use of IP infrastructure from the outset. “With some inherent advantages of network structure and modern, IP-based content
security technologies, IPTV service providers may be in a superior position to more
easily take advantage of this new paradigm.”

Above all perhaps, HTTP is a unicast protocol, supporting one-to-one delivery and as such is well placed to deliver future personalised services. But for this to work there has to be a robust mechanism for content protection and rights enforcement. A significant development therefore was the solution jointly developed by Verimatrix and encoder vendor Envivio to create a unified headend delivering protected SD and HD content via ASP. Announced at this year’s IBC in Amsterdam, this combines the Verimatrix VCAS with Envivio’s 4Caster three screens encoder/transcoder. “This provides a secure convergence point for OTT and IPTV services,” said Kulakowski. “This will enable operators to enhance ARPU, subscriber loyalty and broaden their customer base beyond the limits of a managed network.”

Another argument for ASP is its growing industry momentum, with Apple and Microsoft already on board, and with Adobe incorporating it within the next version of its Flash player release, which will mean it will become a defacto standard for Internet video. But for the final perhaps most compelling word, we should turn to Liz Gannes, editor of NewTeeVee, who has been following ASP particularly closely. “I would say that the advantage of adaptive bitrate streaming is it provides a highly accessible experience for the user,” said Gannes. “The high quality is derived not just from how good the picture looks, but how it doesn't stutter or buffer, regardless of the watcher's environment. That's a vast improvement on systems that cannot adjust between bitrates dynamically, and means that online video can reach a much broader audience as well as provide a reliable experience that's worthy of monetizing.”

In other words it is no good having great average quality if the consistency is lacking.

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