Video Segment Pacing

Introduction

Video segments (or chunks) can be measured by their size in bytes, their length in seconds, and by their pace - the bitrate at which they are played. This Best Practice is concerned with measuring the time and pacing of your video segments.

Background

A segment can vary in time, length, and pacing. In Adaptive Bitrate (ABR) streaming, the length of a video segment is typically between 2 and 10 seconds.

The user's multimedia player can take advantage of ABR if it has the capability to switch among the different bitrate segments—locating the segments that correspond best to the bandwidth on the user’s computer.

The Issue

Determining the pacing of your stream so that it is fast enough to display your video segments smoothly, without being so fast that it drains the buffer and causes stalls, is challenging.

The buffer holds several minutes of video, and the player is trying to achieve the highest bitrate possible without running the buffer too low.

That means the goal is not to ensure the buffer is always full, but rather to prevent the buffer from becoming totally drained.

You need to figure out that balance.

Best Practice Recommendation

The Video Optimizer can measure the pacing of video segments in a video stream, in order to help you determine the most efficient timing.

It is a good idea to review the pacing of video segments when streaming, compare the alternatives, determine the best pace, and implement. If the buffer is always full it probably means the streaming pace is too slow. You should increase the bit rate when the buffer occupancy average is high and decrease it when the buffer occupancy falls too low.

Using the Video Optimizer, and selecting the Video View under Options in the View drop down menu, and then reviewing your trace in Diagnostic tab can help you see how the segments are arriving, and determine the best pacing for your video.

Video and other types of rich media are on the rise in mobile apps and in the future we plan on offering more guidance on streaming and other video technology in our Mobile Development Best Practices recommendations.