Axis Communications Q1602 Q1602 - User Manual - Page 17

AXIS Q1602 Network Camera Video and Audio • Compression. The compression level affects the image quality, bandwidth and file size of saved images; the lower the compression, the higher the image quality with higher bandwidth requirements and larger file sizes. • Rotate image. If required, the image can be rotated. • Maximum frame rate. To avoid bandwidth problems, the frame rate allowed to each viewer can be limited. • Overlay settings. See Overlay, on page 18. Click Save to apply the new settings. H.264 H.264, also known as MPEG-4 Part 10/AVC, is a video compression standard that provides high quality video streams at low bit rates. An H.264 video stream consists of different types of frames such as I-frames and P-frames. An I-frame is a complete image whereas P-frames only contain the differences from previous frames. The GOV length is the number of frames between two consecutive I-frames. Increasing the GOV length may save considerably on bandwidth requirements in some cases, but may also have an adverse affect on image quality. The Axis product supports two H.264 profiles. The Main profile provides higher compression than the Baseline profile with the same video quality, but requires more processing power to decode. The bit rate can be set as Variable Bit Rate (VBR) or Constant Bit Rate (CBR). VBR adjusts the bit rate according to the image complexity, using up more bandwidth for increased activity in the image, and less for lower image activity. CBR allows you to set a fixed Target bit rate that consumes a predictable amount of bandwidth. As the bit rate would usually need to increase for increased image activity, but in this case cannot, frame rate and image quality are affected negatively. To partly compensate for this, it is possible to prioritize either frame rate or image quality. Not setting a priority means that frame rate and image quality are equally affected. You must save your settings before they can take effect. The current bit rate can be set to appear as text overlay. To do this, select the Include text check box option under Overlay Settings and enter the modifier #b in the field. MJPEG Sometimes the image size is large due to low light or complex scenery. Adjusting the maximum frame size helps to control the bandwidth and storage used by the Motion JPEG video stream in these situations. Setting the frame size to the Default setting provides consistently good image quality at the expense of increased bandwidth and storage usage in low light. Limiting the frame size optimizes bandwidth and storage usage, but may give poor image quality. To prevent increased bandwidth and storage usage, the maximum frame size should be set to an optimal value. Stream Profiles A stream profile is a set of pre-configured stream settings including resolution, compression, frame rate and overlay settings. Stream profiles can be used: • When setting up recording using action rules, see Events, on page 30. • When setting up a continuous recording, see Continuous Recording, on page 33. • In the Live View page - select the stream profile from the Stream profile drop-down list. Four pre-programmed stream profiles are available for quick set up. Each pre-programmed profile has a descriptive name, indicating its purpose. If required, the pre-programmed stream profiles can be modified and new customized stream profiles can be created. To create a new profile or modify an existing profile, go to Setup > Video & Audio > Stream Profiles. To select a default stream profile for the Live View page, go to Setup > Live View Config. 17