When viewing a 'live' stream for a monitor ZoneMinder will grab an image from the buffer and encode it into JPEG format before sending it. This option specifies what image quality should be used to encode these images. A higher number means better quality but less compression so will take longer to view over a slow connection. By contrast a low number means quicker to view images but at the price of lower quality images. This option does not apply when viewing events or still images as these are usually just read from disk and so will be encoded at the quality specified by the previous options.