The online video delivery experience
When delivering video online, there are generally two different ways to do it. Progressive download HTTP or Streaming. You might assume that all of the video is streaming, but you’ll be surprised to learn that most of it isn’t.
So what are these two methods? How do they differ? What are the advantages and disadvantages of both? Why would you want to use one method over another?
progressive download
All web servers have progressive download capability. This is simply the method of delivering a video file over HTTP to a browser. This is similar to someone downloading a file from your website. In fact, video is delivered in the same way as an image, CSS, JS, PDF, or any other file on your website.
The real difference is that media players can start showing the video while it is downloading. For example, an FLV file delivered via HTTP progressive download will start playing in your Flash Player as soon as the browser receives a bit of information. The same is true for Windows Media files. QuickTime will wait until the entire file is downloaded before playing it, unless the QuickTime player on the PC/Mac is set to progressive playback. So be careful when posting QuickTime videos.
It’s pretty obvious when a video is delivered via HTTP progressive download. Usually, you will see the small status bar grow as the video downloads. You will not be able to move the scroll button past the amount that has already been downloaded. This makes it impossible to jump to the end of the video before that part has downloaded. If you have a slow web server or limited bandwidth or the end user has a slow internet connection, then the end user may notice buffering.
Buffering occurs when the download cannot get ahead of the video. The video will pause while more is downloaded. If you pause the video and allow a large part to download, you can watch without interruption. In any case, this is a bad end-user experience, this is when I would consider using a CDN.
There is a technology called Psuedo or Seek streaming. This method used TCP/IP range requests to allow the user to jump to any part of the video and the player will make a file range request to download that part. This method is generally only for FLV videos and requires special services or custom Flash servers and players to work.
When a video is delivered over HTTP, it is actually downloaded to the end user’s computer. This is good and bad. It’s good because if the person views the video again, it’s already cached on their computer. It’s bad because it makes it extremely easy for someone to steal your content.
Finally, if someone only views the first minute of your video but doesn’t stop the download, the browser will download the entire file and you’ll pay for delivery of the file even if the person didn’t watch the entire file.
Transmitting video
Video streaming requires access to a streaming media server. Some servers are Flash Media Server, Wowza Media Server, Windows Media Server, Darwin Media Server (QuickTime), Real Media Server. These servers usually require a license and can cost several thousand dollars.
Some well-known streaming protocols are RTMP, RTSP, and MMS.
When a video is streamed, it is sent via the UDP protocol to a player in the end user count. The user will have the ability to fast forward or rewind the video. The video is not downloaded to the end user’s computer, so the content is less likely to be stolen. Also, if the user only watches 5 minutes of a 30-minute video, then they only pay for the 5-minute delivery, not the entire video.
The biggest disadvantage of streaming over progressive download is that if the user watches the same video over and over again, they will pay for delivery each time. Videos are also streamed at whatever bit rate they are encoded at. Keep this in mind when creating HD quality videos. 8 Mbps video might sound and look great, but most homes can’t sustain an 8 Mbps connection. If you have really high bitrate video, consider sending it over HTTP.
Most web hosting providers or content delivery networks (CDNs) will have streaming media servers available for you to use. Historically, Flash video was more expensive to deliver than other forms. Recently, prices have been compressed and you’ll find that it costs about the same to deliver Flash or Windows Media files. In the past, I would have said if your video is over 10 minutes long, send it via Stream and less progressive. Since prices have gone down, I would consider streaming videos of any length, as streaming usually starts playing faster than progressive.
If you’re looking to use a service like CDN or Cloud Computing and they say you can stream your videos, confirm with their tech support that they’re using a streaming server and not just offering bandwidth.
If you are serving Flash video, then you should be serving it over the RTMP or RTMPE protocol for streaming and http for progressive. Windows Media uses MMS or RTSP. Quicktime and Real Media use RTSP.
I hope you find this article of interest? This is a good guide to help you decide whether to use streaming video or HTTP progressive download.
Major content delivery networks that support streaming
* Leaderlight networks
* EdgeCast networks
* DC Networks
*Level 3
* akamai
