Configuring video compression

Compression rate settings

The image is compressed to reduce the size of the video stream. Video isn't compressed when it is displayed on the video surveillance monitor of the server.

An increase in compression rate leads to video degradation. Axxon PSIM compresses video right after it is digitized by the video capture card before recording and/or transmitting it via the network to the Remote Workstations.

Set the video compression rate for each camera individually.

Axxon PSIM uses the Quality setting for the compression rate parameter, which is reverse to the compression rate.

In most cases, the default Quality setting is sufficient.

To change the video compression rate, do the following:

1. Go to the Hardware tab in the System settings window.
2. Select the Camera object created before in the objects tree, which corresponds to the adjusted camera.
3. Go to the Basic settings tab on the settings panel of the Camera object.
   

4. To improve the video quality, move the Recording quality slider to the max position. To reduce the size of the video stream from the camera, move the Recording quality slider to the min.

   Note

   Use the video area to estimate video quality enhancement or degradation.
5. Click the Apply button.

Key frame rate settings

Axxon PSIM uses the Motion Wavelet algorithm for video processing and compression. Processed by this algorithm, the video is the sequence of key and delta frames. A key frame is a full frame of an image. A delta frame (differential frame) is an image containing only pixel blocks that differ from the previous key frame.

Motion Wavelet algorithm guarantees consistency of video quality regardless of key frame rate. With an increase in motion intensity in a frame, the size of the delta frame increases, and the quality of video remains unchanged. With very intense motion (more than 70% of the frame is engaged), the setting of key frame rate is ignored, and every frame is processed as a key frame. 

Axxon PSIM sets the optimal frame rate value by default: every eight frame is processed as a key frame. If there are no special requirements for video size and quality, we recommend keeping the default key frame rate.

To change the key frame rate, do the following:

1. Go to the Hardware tab in the System settings window.
2. Select the Camera object created before in the objects tree, which corresponds to the adjusted camera.
3. Go to the Advanced settings tab on the settings panel of the Camera object.
   
4. Specify the required value of key frame rate in the Key frames interval field.
5. Click the Apply button.

Setting the key frame rate is complete.

Setting the delta frame creation criterion

Axxon PSIM uses the Motion Wavelet algorithm for video processing and compression.

Processed by this algorithm, the video is the sequence of key and delta frames. A key frame is a full frame of an image. A delta frame (differential frame) is an image containing only pixel blocks that differ from the previous key frame. You can compare the pixel blocks of a key frame to the frame that follows the key one by comparing the average brightness of these blocks. If the difference in brightness exceeds a preset value, the block is considered to have fixed motion and becomes a part of a delta frame. Otherwise, the block is considered to have no motion, and it isn't included in the delta frame.

Legitimate values of pixel block brightness are in the range from 0 to 225. The block becomes a part of the delta frame, by default, if the difference between its average brightness in the current frame and in the previous key frame exceeds seven units. Increasing the value of this parameter allows reducing the size of the delta frame and, hence, the size of the video stream, by reducing the number of pixel blocks in the delta frame. Note that blocks with useful motion data now are more likely to be excluded from the processed video, which consequently leads to video degradation. Reducing the value of the parameter that sets the criterion for including blocks in a delta frame allows improving the video quality by increasing its size.

The optimal value of the parameter that sets the criterion for including blocks in a delta frame is determined by the brightness gradient of the video background and moving objects in a frame. You can increase the parameter value with a high gradient and decrease the parameter value with a low gradient.

To change the value of the parameter that sets the criterion for including blocks of pixels in delta frames, do the following:

1. Go to the Hardware tab in the System settings window.
2. Select the Camera object created before in the objects tree, which corresponds to the adjusted camera.
3. Go to the Advanced settings tab on the settings panel of the Camera object.
4. In the Estimate motion field, specify the value of the parameter that sets the criterion for including blocks of pixels in delta frames.
5. Click the Apply button.

Setting the delta frame generation criterion is complete.