While this topic may appear too ‘techie-geekie’ for you to spend time on, you need to take this seriously, for it directly impacts on what your viewing audience experiences – and the eventual success of your live event webcast.
The Quality of live streamed (or any) video depends on two important variables, which we, as Live Streaming professionals must take into consideration, in order to deliver the best possible viewing experience…
Resolution and Bitrate
While these two terms may seem way too technical, they directly impact on what your viewing audience would appreciate – which is why you, as the event manager, should pay close attention to these two terms, which are not as complicated as you might think…
Resolution:
This is simply the size of the video on your monitor screen. The most common sizes today, measured in pixels, are:
- 426 pixels wide x 240 pixels high (240p) – typically used for mobile screens
- 640 x 360 (360p) – the old standard SD, which was actually 640 X 480 pixels
- 854 x 480 (480p) – the current Standard Definition, or SD
- 1280 x 720 (720p) Regular High Definition, or HD
- 1920 x 1080 (1080p) – Full HD
(Note: while even larger resolutions are available, they are generally not used for live streaming as most viewers’ Internet connections could not handle them).
The larger the video, the better the end user’s viewing experience, as it will fill more of their screen – however, the higher resolutions require more ‘bandwidth’ to stream smoothly both for the webcaster doing the streaming and also the viewer who is watching the video.
For example, If a viewer has a slow, WiFi Internet connection, they will not be able to enjoy a Full HD or even a regular HD stream, without the video stuttering, buffering and freezing. Full HD streams will only be good for viewers having a really fast Internet connection, which is measured in what is known as Mbps or ‘Megabits per second’ (more on that term later).
The second variable affecting video quality is Bitrate:
Bitrates are defined as the amount of data (bits) being streamed per second – measured in Bits/second, Kilobits/second or Megabits/second. These days only the last two are applicable as the first is redundant due to the faster Internet connections available today.
1 Kilobit/second = 1000 bits/second
1 Megabit/second = 1000 Kilobits/second
And here is a rule of thumb – the higher the resolution, the higher the bitrate (i.e. data transfer/second) needs to be, for the video to look good. While an HD or Full HD could theoretically be streamed at low bitrates, it would just end up looking terrible.
Here are some recommended values for bitrates as applied to resolutions:
- 240p: 300 – 400 kbps
- 360p: 600 – 800 kbps
- 480p: 800 kbps – 1.5 Mbps
- 720p: 2 – 4 Mbps
- 1080p: 4 – 8 Mbps
Note: Audio bitrates are also important, but much less so than video bitrates, since the data sizes of audio packets are infinitely smaller than video. For streams at 240p video resolution, we recommend using 64 kbps as your audio bitrate. At 360p or 480p, increase the audio bitrate to 96 kbps. At 720p and above, you can use 128 or 192 kbps.
Now why, you may ask, is it necessary for you as an event manager to know all this seemingly techie stuff?
Simple – if you want your viewing audience to have a good QoE (Quality of Experience), you need to know everyone’s Internet speed as well as the streaming venue’s Internet speed.
While it is easy to know the Internet Upload speed of your venue, it is virtually impossible to know every viewer’s connection speeds as they can vary from extremely fast to intolerably slow!
Users with a super-fast Internet connection would certainly enjoy a Full HD stream (1080p at 6 Mbps) but the guys with slow connections would gripe and complain and probably log off the webcast in frustration! Conversely, putting out a single, low resolution stream at low bitrates, could be viewed by all your audience, but the QoE would be severly lacking for those with a fast Internet connection.
So what is the solution?
The Solution is a ‘Multi-bitrate’ Broadcast.
This is where your webcaster would be sending out multiple streams simultaneously. For example…
- 240p at 400 Kbps (for mobile devices)
- 480p at 800 Kbps (for slower connections)
- 720p at 2 Mbps (for regular connections)
- 1080p at 4 Mbps (for high speed connections)
Assuming the venue has enough bandwidth to support a total Mbps of all four streams (which in this case would add up to 7.2 Mbps X 2 = 14.5 Mbps) which most hotels and conference rooms typically do, you would be catering to the needs of all your viewers, without the inevitable frustrations of a single stream webcast.
But how, you may ask would the viewer’s browser and video player know to select which stream speed? Surely they cannot view all 4 speeds simultaneously!
This is where an Adaptive Video Player springs into action! Old video players could only handle one stream at a time. Modern Adaptive Video Players on the other hand, have the technology to detect the viewer’s local connection speed on the fly and select the correct stream out of the four, to match the viewer’s exact requirements.
So if you, as the event manager, truly care for your audience’s QoE, you would be:
- Inquiring as to how your webcaster intends to stream the video.
- How much bandwidth your event venue can offer for streaming.
At MediaStreams Communications, we routinely stream live video using Multi-bitrate Streaming, assuming the venue can handle the outgoing bandwidth – which they usually do.
Call us at 604.970.5055 or visit our website to send us an email, for more information on how we will ensure the success of your Live Event Webcast.