Sometimes Error 91 is confused with other common HCNetSDK.dll issues. Knowing the difference helps in rapid troubleshooting: Error Code Common Fix Reconnecting not supported Disable "Auto-change Stream" Error 5 Max connections reached Reboot device or log out other users Error 302 Device not connected/disabled Check network cables and IP Ping status Error 1602 Failed to initialize Run iVMS-4200 as Administrator Technical Summary
If the error occurs specifically during playback or when viewing multiple screens:
The software may be trying to switch automatically between Main Stream (high quality) and Sub Stream (lower quality) based on window size, but the camera or NVR doesn't support that specific command. hcnetsdk.dll 91
According to use-IP LTD , exceeding decoding capabilities is a prime suspect for stream-related failures. Reducing the bitrate can free up the "resources" the SDK needs to maintain the connection. 4. Update Firmware and Software
The most frequent cause is the software trying to manage bandwidth by switching streams. You can disable this in iVMS-4200: Go to -> System Configuration . Select the Image tab. Look for the option Auto-change Stream Type and uncheck it. Sometimes Error 91 is confused with other common HCNetSDK
Understanding and Resolving Error Code hcnetsdk.dll 91 The error code hcnetsdk.dll 91 is a common issue encountered by users of Hikvision security systems, specifically when using management software like iVMS-4200. This error typically displays a message such as "Reconnecting it is not supported by the device" or "The device does not support the operation." It essentially means that the software is attempting a task—often related to live viewing or stream switching—that the hardware or current configuration cannot execute. What Causes the hcnetsdk.dll 91 Error?
Visit the Hikvision Support Center to find the latest firmware for your specific model. Reducing the bitrate can free up the "resources"
If you are trying to view too many high-resolution cameras at once, the NVR or PC might run out of decoding resources, triggering a generic 91 error.