VIN0 to HDMI latency measurement (Naon)
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IntroductionEdit
Several video applications need to acquire a video stream and to display it on an LCD panel or similar device. In some cases it is required that the latency measured between source stream and stream feeding LCD panel is within a specified time (often expressed in terms of fields).
This article describes how it has been performed the measurment of such latency on Naon platform. Texas Instruments provides documentation and software to perform similar measurements: http://processors.wiki.ti.com/index.php/Latency_Measurement_on_Capture_Encode_Decode_Display_Demo. Method suggested by TI is completely software-based. Since Linux is not an RTOS, the intrinsic error of such method might not be tolerable where the application has hard real-time latency requirements. Thus a hardware-based approach has been implemented to build ad hoc testbed as described in the following section.
TestbedEdit
The following picture shows a simplified block diagram of the testbed.
As source a NaonEVB-Lite/Naon system has been used playing an ad hoc video stream. The stream is output via HDMI port that, in turn, is connected to HDMI splitter. One of the output of the splitter feeds a LCD display that is used by the operator to monitor the whole process.