Measuring Video Quality

One way to measure video quality is to limit the number of captured frames dropped during the capture operation. When streaming capture has finished, the quality value is compared with the ratio of dropped frames to total frames. If the percentage of dropped frames is greater than the value of the wPercentDropForError member of the CAPTUREPARMSRYJ.8W structure, AVICap sends an error message to the error callback function if it is installed.

You can retrieve the current limit of dropped frames (expressed as a percentage) by using the WM_CAP_GET_SEQUENCE_SETUP1GNHJI message (or the capCaptureGetSetup1A5QZ0N macro). You can set a new limit by specifying a percentage as the value of the wPercentDropForError member of the CAPTUREPARMS structure, and then sending the updated structure to the capture window by using the WM_CAP_SET_SEQUENCE_SETUPYGBQ.R message (or the capCaptureSetSetup115V26W macro). The default value of wPercentDropForError is 10 percent.