The Turbo 4 Hybrid DVR K series has multiple models and across different platforms and chipsets. It also has similar firmware development of other recording product lines, DVR K series has also introduced the GUI4.0 to ensure the series to be compatible with the newest technology available. The new database architecture is also brought into the DVR firmware v4.0 to be future-proof and for a better recording search experience. 

Throughout the different firmware version development, the series has also been experienced a few obstacles, This knowledgebase will explain in detail the recording and playback issue DVR has been encountered and also provide solutions to ensure the system will work properly moving forward.

Device List 


All DVR K series platforms. 

Platform: K71, K72, K51, K52, K72A

For a complete Model and Platform matching list, please see attached sheet.

Affected Firmware Version: 

v4.20.000 build 190619

v4.20.000 build 190430

v4.20.000 build 191114

All versions above support the Database Rebuild function at the local & web GUI


Playback issue after GUI4.0

    -Local Playback is slow and unresponsive

    -No recording indicator within the calendar or missing a big chunk of the period with recording. 

    -When playback video, the video either jump to a different timestamp or plays back wrong channels 

    -Channel is under a continuous recording schedule but the recording display bar is not solid throughout

Recording still missing after database rebuild - Recording Data may have been overwritten falsely due to a Database issue. 

    -Recording data is searchable but unable to playback or playback blank video.

    -Multiple channels are still missing recording after performing the Database Rebuild successfully. 


Playback issue after GUI4.0

Database Recording Data Structure was developed from B-Tree data structure to MySql database structure when introducing the GUI4.0. It is intended to improve the better playback searching mechanism and to support a bigger data structure in the future. When writing the data to the database, system firmware has falsely indexed the data block, in a result causes the system not able to search the correct data recorded.

Recording still missing after database rebuild 

Due to the database issue, the system may have then falsely overwritten the data because of wrong indexing/pointer in the memory block. 


K series DVR firmware is based on DVR chipset platform. In order to properly apply to the correct firmware to the particular model, please refer to the firmware matching chart above. DVR will not accept the firmware upgrade if the version was designated for another platform.

DVR-K72_ML_STD_V4.20.002 Build 210705

DVR-K71_USA-ML_STD_V4.20.002 Build 210705
K72ADS-7204HQHI-K1(/P) Hardware B
DVR-K72A_ML_STD_V4.20.002 Build 210705
DZ_K52_ML_STD_V4.20.002 Build 210705
DZ_K51_ML_STD_V4.20.002 Build 210705


1. Upgrade the DVR according to the chart above. 

2. Reconfirming Channel's Recording Schedule 

    - Confirm the channel's recording schedule is enabled. 

    - Check if the channel is on the correct recording schedule.

3. Storage Setting

     - If the Storage setting is in Group Mode instead of Quota mode, make sure the channel is assigned to the HDD group. 

Note: After DVR has been upgraded to the latest version. Older recording data may appear completely unsearchable. This is a clear sign of DVR had a database issue on the previous firmware version.  Please perform the database rebuild from the steps below to retrieve all the recordings.


4. Perform Database Rebuild (repair) locally. 

   - Some versions above support Database Rebuild via web access - K51 and K72

   - Perform Database Rebuild regardless if the system is having any database issue symptom. 

   - Database Rebuild process is average ~30 to 60min per TB. The process may still vary depends on recording data.

   - After Database Rebuild - Check log to confirm Database Rebuild has went thru properly. 

       - If Database Rebuild Started and Stopped log has been log only within few mins. Database rebuild may not

         has been completed properly. It is STRONGLY recommended to reperform the Database Rebuild.

       - To check log > System > Log > Information > Database Rebuild Started and Stopped. 

       - If the log option is not available - access system via SSH can also obtain similar results. 

5. Recording Data is still missing after database rebuild process. 

    If the data has not been recorded or has been overwritten, Database rebuild process is not able retrieve those lost 

    data. Have the system upgraded to the latest available firmware version above to prevent any future data lost is

    strongly recommended for ALL application. 

Note: Please do advise all customers to upgrade all DVR K series firmware to prevent any possible future recording data loss.