Jock Mirow, Radiant Technologies’ Director of Live Streaming, outlines the differences between RTMP and HLS.
In the battle for the definitive streaming codec & delivery methodology, a return to the simple things may win the day.
As the streaming market evolves into a game-changer for the Media & Entertainment industry, the background technology battle rages in the CDNs and servers that are powering this transformation. We’ve shifted from dependence upon terrestrial delivery limitations into a fully digital ecosystem that (like all digital products) continues to evolve organically whether we like it or not.
Real Media, Windows Media, and Flash Video – all fallen by the wayside in the quest for superior delivery to the consumer – for reasons as varied as their delivery methods. Then RTMP (Real Time Media Protocol) appeared out of the ashes with a relatively dependable server-to-player path that allowed for feature-length film delivery in a fairly dependable fashion – at least dependable enough to begin charging subscriptions and pre-rolling ads in players.
But while RTMP was speedy and dependable (to a point) there were issues: the entire chain of delivery had to have pretty healthy bandwidth AND the ability to handle a unique delivery protocol. Bad news – your destination could not depend upon a browser, it had to have a player that could decode RTMP and it required port 1935 to be open to receive data. This means it was often blocked by firewalls. Intentional or not, this could cause unpredictable results and bad end-user experiences – especially in corporate environments.
The solution was simple and evolved from a previous technology – the m3u8 playlist. For years audiophiles has been stringing together MP3s using the m3u8 file specification – which simply said: play this MP3 then play the next MP3. So the natural evolution was: play this MP4 then play the next MP4 (video). The problem was, MP4s were often feature length, unlike 3-5 audio files. So the natural solution was to take video and break them into chunks of standardized video: namely MPEG. MPEG & MPEG2 have been used by DVD discs for years, mainly in the. TS form of video segmentation. If you take a look at the contents of a DVD from a file perspective, you find things like intro.ts, feature.ts, and bonus.ts – all of which are discrete video segments that the DVD menu can call individually.
These aforementioned TS segments were often large and unwieldy – so HLS sliced these large files into smaller “chunks” – easily delivered by simple progressive download over HTTP. Thus the new HLS (HTTP Live Streaming) was born. Note: HDS (HTTP Dynamic Streaming) was similar in delivery concept – but was mainly used for Flash delivery from Adobe, and thus doesn’t command much of a market share. HLS was originally developed by Apple but has since become an open standard.
Next: What Makes HLS So Special?
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