Tuesday, October 04, 2016

Internet Video Heading For A Traffic Jam


Stuck on the M1 in traffic, rows of cars to my left, to my right, in front of me and behind me, bumper to bumper and going nowhere, a Virgin Rail train sped past on its electric line at 125Mps. It was a salutory metaphor for the latest aberrant evolutionary step in video technology. Forget VHS over Betamax, the issue is HLS over RTMP.

Now, at a time when the BBC seems to be struggling in delivering its streams and Netflix went black for three hours, the technology underpining IPTV isnow not a nice to have in place of broadcast, cable or satellite, it's an essential technical component of TV delivery,mbe oming more important by the day.

The trouble is, everyone has bet the future on the jammed motorway, not the railway. 

To understand this I'm goin to have to explain a bit about the technology.

In the early days of the internet, video files were large and connections were poor. Getting one to fit onto the other was a problem. The internet works by breaking data into packets and then transferring these individually using something called hypertext transfer protocol - you'll recognize this as the http at the beginning of web addresses. Http is a protocol that slices up the file at the nding end (the server) and reassembles it at the receiving end (client or browser). This works well for stuff that's not time sensitive and it's why images generally take longer to appear than text on a web page.

But it doesn't work well for video. 

So, a bunch of guys who broke away from Microsoft created Real Time Streaming Protocol and the educational interactive software developer Macromedia simultaneously developed Real Time Messaging Protocol, both of which developed a more 'broadcast' orientated way of delivering content. There were issues, such as the use of special ports which could be blocked by firewalls, but these two protocols were rapidly adopted in technology such as Real Networks and Adobe Flash and for many years became standard for streaming live over the internet.

Amongst the many advantages of these protocols are latency (the delay in getting the picture to you is low), efficiency, reliability and security. Quickly added to this was incumbency, and as Flash became a standard multimedia component for web browsing, RTMP seemed to have won the day.

The downside is that they were both proprietary, so a licence was payable for every use. Worse still, Apple did not own either protocol, so the company sought an alternative.

They struck upon the wheeze of using an audio playlist format (.m3u8) to segment the video file and then to have it transported as multiple small broadcast video files (MPEG-2.TS) over http and then it is reassembled in the browser. With the advent of the iPhone and iPad this became the only way of delivering live video to these devices and the cast was set.

It should be added that HLS does have the advantage of supporting the ubiquitous, but, oh, proprietary again, H.264 codec.

As with VHS, the inferior technology has, in many ways, won the day for commercial not technical reasons.

As I write most major content delivery networks (CDNs) are quietly dropping RTMP in favour of HLS since this can leverage non-proprietary technology (ie plain old file caching) for delivering video and does not require paying a fortune to the likes of Adobe (who acquired Macromedia).

Perhaps ironically, HLS is still not set as an approved standard in any way, and the CDNs are anyway paying licences to companies such as Wowza, who provide the transcoding and segmenting capabilities

RIP RTMP and RTSP. Thank you for your decades of loyal service. I can't help thinking that you were Concorde in an EasyJet world.



https://en.wikipedia.org/wiki/HTTP_Live_Streaming
https://en.wikipedia.org/wiki/Real-Time_Messaging_Protocol
https://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol