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What Are Mainstream And Substream? How to Calculate Monitoring Storage Quickly?

What is the difference between substream and mainstream? Why is the monitoring always stuck? How to calculate the monitoring hard drive capacity quickly? In this article, we will look at relevant content together.

Ⅰ. The difference between substream and mainstream

Hikvision was the first to propose the concept of mainstream and substream, the aim was to solve the problem of reducing the bit rate to satisfy the fluency of remote preview without affecting the dual-stream technology of local recording under bad network conditions. After one video enters the NVR, it can encode main stream and sub-stream. The resolution of the mainstream is higher than that of the substream. Mainstream is used for recording while substream is used for network transmission.

This is called dual-stream technology. The purpose is to solve the quality problems of local storage and network transmission of monitoring video.


Dual-stream can achieve two different bandwidth stream requirements for local and remote transmission. The mainstream can be used for local transmission to obtain clearer storage video. The substrate can be used for remote transmission to obtain smooth images and recordings due to bandwidth limitations.

The recorder can encode mainstream and substream when one video is entered. The mainstream is used for local recording while the substream is used for network transmission. The default is the local access of the recorder, and the mainstream is displayed automatically. The automatic substream display can be achieved by remote access. Therefore, if there is stuck when you are monitoring access remotely, you can try to reduce the substream to solve the problem.

In general, the mainstream is larger with higher definition and higher bandwidth. The substream reduces the image format under the image environment of the mainstream, and it has a lower resolution and smaller bandwidth than that of the mainstream. In general, the mainstream is used for storage and the substream is used for network transmission. The mainstream is stored locally while the sub-stream is suitable for image transmission on low-bandwidth networks.

The purpose is to improve the smoothness of the network browsing without changing the local video effect when using the substream to preview under bad network conditions by reducing the bit rate of the substream.

Based on the above theory, we can understand why people are always asking such questions: Why is the video monitoring image blurred using substream?

Why does the network camera drag the screen with the mainstream? However, it is fine with the substream?

The mainstream has the highest pixel resolution mode while the substream has a low pixel and low-resolution mode.

The mainstream has the high image quality and high bandwidth requirements. There are solutions to problems such as drag screen, stuck screen, and bad connection:

1. You can use the substream with low image quality to improve the smoothness of picture transmission.

2. You can lower the frame rate and resolution of the code stream in the setting to reduce bandwidth requirements.

3. You can increase network bandwidth to meet high-quality transmission requirements.

Ⅱ. How to quickly calculate the daily storage capacity of the camera?

We have already known the difference between the mainstream and the substream. Therefore, how to calculate the daily storage capacity of the camera? This is a frequently asked question. We will draw a summary and find an easy method.

The camera code stream or the bandwidth of the monitoring video stream is divided into mainstream and substream. The mainstream is used for storage, and the substream is generally used for preview. Therefore, the video that everyone sees during playback has higher quality than that seen during the preview. Also, the bit rate varies with different resolutions/frame rates and picture effects.

Different coding and compression algorithms lead to different H.264 and H.265 bitstreams. The current mainstream encoding is H.265, which can save nearly half of the transmission bandwidth and storage usage compared with H.264.

1. Hard disk capacity

Hard disk capacity refers to the storage space of the hard disk. In general, there are 1T/2T/3T/4T/6T, 1T=1024G, 1G=1024M. It should be noted that the actual capacity of the hard disk for video storage is 90% of the total capacity with a capacity factor of 0.9. Why?

This is because the standard of hard disk manufacturers is decimal with 1G=1000MB=1000000K while the system uses binary with 1G=1024MB=1048576KB.

2. Calculation method

Video storage size = Mainstream (M) ÷ 8 × 3600 (seconds) × 24 (hours) × number of monitoring channels × number of recording days

Assuming that the HD header of a project is 1080P in H.265 format (the mainstream is about 3M), 50 channels, and stored for 90 days, the calculation formula is as follows:

3M (mainstream) ÷ 8 × 3600 (seconds) × 24 (hours) × 50 (monitoring channels) × 90 (recording days) ≈ 145800000MB

Converted to T: 145800000MB÷1024÷1024≈139T. If the actual capacity of the hard disk is 90%, it is 139T÷0.9=154.4T, which means you need a total of 154T hard disk to meet the storage requirements, and you can prepare 160T.


Mainstream ÷ 8, the monitoring code stream is measured in bits.

There are various calculators for direct calculation now. However, it is better to be able to quickly estimate in daily projects.


监控硬盘容量计算:Monitoring hard disk capacity calculation



1路:1 Route

码率:Code rate

(1) 960P refers to the resolution of 1280×960, which is equivalent to 1.3 million pixels:

H.265 storage is about 22G per day (1G per hour).

(2) 1080p refers to the resolution of 1920 × 1080 pixels, which is equivalent to 2 million pixels:

H.265 storage is about 32G per day (1.3G per hour).

(3) 3mp refers to a resolution of 2048*1536 pixels, which is equivalent to 3 million pixels:

H.265 storage is about 45G per day (1.9G per hour).

4mp, 5mp, and 8mp correspond to 4 million, 5 million, and 8 million pixels. You can check the table above.

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