Introduction
Many IP video solution providers claim to have products that offer multi-streaming. In this article, we will explain briefly what multi-stream is, methods of multi-streaming, and its advantages.
To start with, let’s understand what multi-streaming is. Multi-streaming denotes the ability of a video server to provide two or more types of video streams, with different properties, to different users and/or applications.
In most cases, multi-video streams can be differentiated based on any of the following properties:
- Compression type (H.264, MPEG4, MotionJPEG)
- Resolution
- Frame rate
Methods of Multi-streaming
Multi-streaming by Compression Type
A common method to provide multi-streaming facility is to provide streams that make use of different video compression types. IP video devices that incorporate such a method generally stream H.264 and MPEG-4 video separately.
Multi-streaming by Resolution
At times, it may be ideal for the IP video device to stream video at two different resolutions. The lower-resolution stream is usually useful for applications over the internet or mobile devices that are only capable of handling such streams, because of bandwidth constraints. However, sacrificing resolution is generally considered the last option for the purpose of video surveillance.
Dual Stream by Frame Rate
Reducing the frame rate is perhaps the easiest way to reduce the bit rate of a video stream. While the motion is not as fluid as full-frame video, no details are lost. For professional video surveillance, video quality and resolution are valued over frame rate.
Why Multi-stream
The purpose of multi-streaming is to provide video streams to multiple downloading applications and/or devices at different bit rates. As bandwidth of an existing network environment is rarely unlimited, it is important to monitor and constrain the amount of traffic each streaming device uses. Also, multi-streaming can be applied depending on type of network access, whether it’s streaming video over a local LAN or across the internet. For example:
- Live preview at higher resolution, record at lower, and/or vice versa (for the reason of storage space optimization)
- Higher frame rate within a LAN, lower via the Internet (for the reason of bandwidth optimization)
- Certain surveillance situations using the H.264 codec, viand certain using MotionJPEG (for the reason of better compression efficiency).
To summarize, multi-streaming allows a user to define and get a video stream delivered in a different resolution, frame rate, and compression type to meet requirements of individual quality, storage constraints, bandwidth demands, codec efficiency, and CPU usage.
