This article is an adjunct to a previous post on Live HD Streaming – “So You Want to Webcast in HD – Why?”
It is important for event managers to know the pros and cons of Streaming High Definition Video Live, if they are to provide a seamless user experience to their online audience.
Although most traditional on-demand HD-quality streaming systems like YouTube use elaborate buffering techniques that reduce significant latencies, their advanced techniques and algorithms are not easily (or cost-effectlievly) adaptable for real-time live-streaming environments.
Three of the main design parameters for HD live streaming are:
- The video quality (mostly determined by the resolution of each video frame, the number of bits allocated for each of the three transmitted colors, the number of frames per second, and the compression technique used)
- The available transmission bandwidth
- The end-to-end delay.
Due to the massive amount of data required to transmit multiple video streams simultaneously, achieving low latency and keeping the bandwidth low are contradictory requirements.
Other problems in streaming HD live video are Packet losses and transmission errors. Because errors in one video frame may propagate to subsequent frames when certain compression algorithms are used, small transmission errors may result in significant picture quality degradation over a period of time. Also, many live streaming systems do not recover packet
losses in order to reduce end-to-end delay.
Increasing broadband penetration and faster devices make high-quality viewing experiences possible, but network latency issues and heavy traffic loads can often result in disappointing video streaming performance, with frequent pauses for re-buffering – not to mention the increasing number of viewers using mobile devices on cellular networks creates its own set of challenges.
Its also very important to consider playback.
If you are streaming to a consumer or even business audience, it’s more than likely that not everyone will have enough bandwidth to view the HD video without pauses and disruption – and this is especially important if your viewers are paying for it.
Given that, you should plan on doing two streams – one 720p and another at 480p or even 360p – so that the viewer with low download bandwidth can still watch the video. This, of course, means you need additional upload bandwidth for the two streams from the event venue.
Also, there is the choice of having the viewer manually choose between two different streams or using adaptive or dynamic streaming that is supported by many CDN’s (Content Delivery Networks). In this latter case, the user just watches the stream and the technology detects their download speed and choose the correct stream – an ideal solution that however, increases cost and bandwidth requirements.
As you can see, HD video streaming is a somewhat complicated process to implement. But once you get it all setup, you really can create a very nice user experience with 720p going to viewers with enough bandwidth and lower resolution/bitrate streams automatically going to users with lower bandwidth.