Direct answer
Use the substream for multi-camera grids and routine checks; open the main stream only when detail is needed or when recording policy requires it. Verify both paths and label them clearly.
Why this happens
A grid that decodes every camera’s highest-resolution stream can waste bandwidth, heat the viewing device and increase startup time. The substream exists to reduce that load, but may be too soft for identification or evidence.
Treat the URL, credentials, address family and RTP transport as separate variables that can fail independently.
A controlled test
Measure bitrate, resolution, frame rate, codec and startup time for both profiles on the actual camera.
Change one variable at a time. Keep the camera model, firmware, endpoint and account recorded; then test network reachability, protocol response, media transport and decoding as separate layers.
Use a dedicated view-only account and a trusted local diagnostic tool. Redact credentials, private addresses and identifying data before sharing output.
Diagnostic sequence
| Check | Action | Evidence of progress |
|---|---|---|
| Grid | Load the substream in every normal tile. | All cameras remain responsive at expected scale. |
| Detail | Open the main stream on demand. | Fine detail is available without burdening the whole grid. |
| Codec | Prefer a broadly supported codec for the substream. | Every target device decodes it. |
| Labels | Name profiles by purpose, not vendor numbers alone. | Operators choose the intended stream consistently. |
Evidence to keep
Keep a small profile table per camera. It turns “high” and “low” into measurable resolution, bitrate, codec and use-case choices.
Boundary and safety note
A substream is not automatically secure or reliable; it uses the same account and network trust boundaries as the main stream.
For remote viewing, use a managed VPN instead of exposing RTSP or camera administration ports directly to the public internet.
SmartRTSP
SmartRTSP is a camera-focused RTSP and ONVIF viewer for Apple devices, Windows and Android. It fits direct viewing, discovery and multi-camera checks; keep a dedicated NVR or VMS when continuous recording, evidence export or centralized enterprise controls are required.
Frequently asked questions
Does the substream reduce camera image quality?
It is intentionally lower in bitrate or resolution, but the main stream can remain unchanged.
Should an NVR record the substream?
That depends on the retention and detail requirement; many systems record the main stream while viewers display the substream.
Can main and substreams use different codecs?
Many cameras allow it, which can make H.264 useful for compatibility while H.265 is retained for recording.
Primary references
- IETF RFC 7826 — Real-Time Streaming Protocol 2.0
- ONVIF — Profile T for advanced video streaming
- SmartRTSP — official platform and product information
Related SmartRTSP guide
Open related guideChoose a high-detail main stream for inspection and a lower-bitrate substream for grids, remote links and constrained devices.