Dynamic streaming in Flash Media Server 3.5 – Part 1: Overview of the new capabilities

The need for dynamic streaming

With faster-performing client hardware and users with higher bandwidth becoming the norm, the promise of high-definition (HD) video on the web is a reality. HD web video is generally considered larger video starting at 640 × 480 pixel dimensions and increasing up through 720p towards 1080p. The issues facing this trend have been around since the beginning of streaming video. Now Flash Media Server and Flash Player can handle streaming HD video in ways that greatly improve the user's experience without the need for them to do anything besides sit back and enjoy high-quality material.

One of the biggest issues facing publishers trying to stream longer duration (longer than five minutes) and higher quality video—especially HD video—is the standard fluctuations of users' Internet connections. This is a standard issue on most networks and can be exacerbated when multitaskers, wireless network fluctuations, or multiple, simultaneous users sharing a connection are involved.

The end result is a moving target for actual available bandwidth, and this can leave users continually having to rebuffer and wait for their video if the selected stream bandwidth is unsustainable on their network. Dynamic streaming detects fluctuating bandwidth and switches among streams of different bit rates in order to match the content stream to the user's bandwidth (see Figure 1).

Figure 1. Matching bandwidth changes to maintain QoS

On the other hand, some users may start the stream with low available bandwidth, and then free up more bandwidth after the start of the video. In this scenario, dynamic streaming can offer the ability to up-scale the video quality to a higher level, once again improving the user's experience.

In the past, the alternative was to perform initial or frequent bandwidth detection routines. Although better than nothing, these tests were costly in time and often didn't provide the accuracy needed due to the normal fluctuations and changes in bandwidth. Now, with the dynamic streaming capabilities and Quality of Service (QoS) information available, bandwidth detection tests have lost much of their value.

Another issue that can hinder playback, especially with large-dimension HD video and full-screen playback, can be the user's hardware performance limitations. If the CPU cannot decode the video stream fast enough, it will result in dropped frames, which can adversely affect the smoothness of the user's video display. In this case, using a lower-quality video file would enable less strain on the CPU to decode in synch and maintain performance.

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