What is dual stream? How to configure the main code stream and sub-code stream
Explain the function and typical configuration of dual streams, and explain the optimization method when multi-channel mobile phone preview is stuck and remote access bandwidth is insufficient.
What is dual stream
The camera outputs two streams of different parameters to the same picture at the same time:
- Main stream: High resolution and high bit rate, used for local recording and viewing of key images.
- Sub-stream: low resolution, low bit rate, used for multi-screen preview, mobile phone remote access and bandwidth-limited scenarios.
Some models also have third code stream (lower code rate), which is specially designed for mobile terminals or intelligent analysis.
Typical configuration reference
| Purpose | Resolution | Bit rate | Frame rate |
|---|---|---|---|
| Main stream (recording) | Same as the camera’s native resolution (such as 2560×1440) | 4～6 Mbps | 25fps |
| Substream (multi-picture preview) | 640×480 or 704×576 | 0.5～1 Mbps | 15～25fps |
| Third stream (mobile phone) | 320×240 | 0.2～0.5 Mbps | 10～15fps |
Why you need it
- Reduce client pressure: Simultaneous preview of 16 4K main streams requires extremely high-performance clients and networks, and sub-streams can be easily implemented.
- Saving remote bandwidth: It is almost impossible to watch the main stream smoothly in a 4G mobile phone environment, but sub-streams are feasible.
- Reduce decoding pressure: When NVR and splicing screen are installed on the wall, sub-stream can significantly reduce the chip load.
- Intelligent analysis independent stream acquisition: The analysis server only needs to obtain the sub-stream, which does not affect the recording quality of the main stream.
Common troubleshooting
- Multi-screen freeze: Check whether the client misuses the main stream preview and switches to the sub-stream.
- Black screen in mobile phone preview: The third stream is not enabled on some models and needs to be enabled on the camera side.
- Blurred playback: The playback takes the main stream. If it is also blurry, it means that the bit rate of the main stream is set too low.
- Remote access is slow:In addition to substreaming, you can reduce the frame rate, enable P2P, or configure port mapping to optimize the link.
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