It’s the second week of the Beijing 2008 Olympics and though the press coverage of the NBC Olympics website has been more than thorough, one thing that hasn’t been fully explained is – what exactly are you watching when exploring the different parts of the NBCO video player – and what kind of quality should you expect anyway?
Let’s begin by explaining the 2 video player user interfaces and the plugins that power each.
The NBC Olympics video player is available in 2 flavors: Standard and Enhanced. The Standard player UI is what you get when you first launch the video player. The Enhanced player UI is what you get when you click on the “Enhanced” button in the lower right corner of the Standard player.
The Standard player has a video rectangle of size 592×336 (roughly a 16:9 aspect ratio) and can be experienced with either WMP or Silverlight plugins. As explained in earlier posts, if you are running Windows OS + Internet Explorer or Firefox browser + WMP9 or better (ideally WMP11), you can choose to use the WMP plugin instead of the Silverlight plugin to view video by choosing “Watch without Plugin” when prompted to install Silverlight. The video streams available in the Standard player are identical regardless of whether you’re using WMP or Silverlight. The bitrate of those streams never exceeds 650 kbps in the Standard player.
The Enhanced player is only available to those who have installed the Silverlight plugin. It provides a more interactive experience and features a larger video window, as well as higher resolution and higher bitrate video streams (for some content). The video rectangle is 848×480 (also roughly 16:9 aspect ratio).
Video and Audio Codecs
All video on the NBC Olympics website is encoded as VC-1 Advanced Profile in CBR mode at various bitrates (described below).
All audio is encoded as WMA 10 Professional audio at 48 kbps, 44.1 kHz, stereo. The special Low Bitrate (LBR) mode of the WMA Professional codec offers improved fidelity over the more commonly used WMA Standard codec and is comparable with HE-AAC quality.
The content is generally divided into 2 categories: Live/Rewind and Highlights/Encore.
Live video (and its archived counterpart Rewind) is encoded on site in Beijing, then beamed back to New York and distributed to homes via CDNs. It comes in 2 bitrates and sizes:
- 592×336 at 600 kbps
- 320×176 at 300 kbps
The reason why higher bitrates aren’t offered for Live streams is because NBC’s link from Beijing to New York has a fixed bandwidth and needs to be able to sustain many simultaneous live streams (1 Mbps per event, and there can be as many as 30 events happening at the same time). In addition, delivering more than 1 Mbps of video around the world without losing packets all over the place or running into last-mile bottlenecks – is still incredibly difficult even in 2008.
Highlights/Encore video is content produced and encoded by NBC in New York. It typically features highlights, previews, recaps, interviews – so generally anything that’s not a full rewind of an event. It comes in 4 bitrates:
- 320×176 at 350 kbps
- 424×240 at 600 kbps
- 592×336 at 1050 kbps
- 848×480 at 1450 kbps
As mentioned above, the higher bitrates are only available in the Silverlight-exclusive Enhanced player interface. The Standard player is only able to consume the first 2 lower-bitrate streams.
In addition to all the bitrates and resolutions mentioned above, all content is available for thumbnail-sized Picture-In-Picture viewing. PiP video is always encoded as 128×96 at 50 kbps and half the source framerate.
This means that the minimum bandwidth needed to view the highest quality video + PiP is 1550 kbps (1450 video + 48 audio + 50 PiP) in perfect conditions. In reality, you probably need at least 100 kbps overhead on top of that in order to compensate for Internet unreliability.
Much of the press coverage of the NBC Olympics website has referred to the video content as being ”HD quality.” The definition of “HD” for television has always been pretty clear: you need at least 1280×720 to call something “HD.” Unfortunately, the definition of HD video on the web has been far more ambiguous. It’s the YouTube effect. Once you get used to watching 320×240 poorly compressed video for so long, anything above that suddenly starts looking like Digital Cinema. :) Whether or not you choose to think of 848×480 video as HD is up to you. I personally wouldn’t, but then again – it’s my job to be nitpicky about video quality.
Finally, there’s the actual delivery of the content. Two basic methods of streaming are used on the NBC Olympics website.
All Live video – regardless of which plugin is consuming it – is streamed via WMS HTTP streaming protocol from Windows Server 2008 servers running Windows Media Services. The same streaming method is also used for all delivery to the WMP plugin. If you’re using the WMP plugin, you always get the WMS stream, regardless of content type.
As mentioned before, the Silverlight-powered Enhanced player has several features that make it a superior experience to the Standard player and WMP plugin. One of them is its ability to seamlessly switch between streams of different bitrates and resolutions during playback to dynamically match the user’s bandwidth and CPU power. This feature, often referred to generically as Adaptive Streaming, is something that Microsoft developed for NBC based on Silverlight 2′s MediaStreamSource interface. NBC’s website does not utilize the Move Networks adaptive streaming technology, as has been widely rumored. Silverlight 2 supports hooks to multiple adaptive streaming approaches, including Move’s - but in this particular case Microsoft provided the solution.
The easiest way to recognize that you’re watching an adaptively streamed video while in the Enhanced player is by seeking to another point in the video. If the player is using adaptive streaming, you will see the video start up very quickly without a buffering notification and the resolution will briefly drop. After a few seconds the blurry video will get sharper, and then sharper again… and then sharper again, your bandwidth allowing, of course.
Summary – Setting expectations
Here’s the best quality you can expect for NBC Olympics video, as well as minimum requirements:
- Live/Rewind content:
- Either plugin: 592×336 at 650 kbps
- Highlights/Encore content:
- WMP plugin: 424×240 at 650 kbps
- Silverlight plugin and Enhanced player: 848×480 at 1500 kbps