Analog or serial digital video input with automatic video switch
View Patent ↗An instrument has a single video input port for receiving either analog or serial digital video signals coupled to both an analog and a serial digital video input path. The outputs of the analog and serial digital video input paths are provided as respective inputs to a video switch, the output of which is then provided to the instrument for further processing. Information from the serial digital video input path, which may include clock recovery lock, carrier detect and/or video standard, is provided to a decision module that generates a select signal for the video switch. As an example, if “lock” is present, then the output from the serial digital video input path is selected automatically for output by the video switch, otherwise the output from the analog video input path is selected automatically. The automatic selection for the switch may be manually overridden. A text display is provided to indicate which video input path the instrument is processing according to the output from the video switch, as well as information about the video signal at the video input port.
1. A video test and measurement instrument comprising:
means for coupling a common video input port to an input of an analog video input path and an input of a digital video input path, each video input path having a separate output;
means for automatically switching between the separate outputs in response to information derived from the digital video input to provide an output video signal corresponding to the video format of a video signal applied to the common video input port.
2. The instrument as recited in claim 1 wherein the automatically switching means comprises:
a video switch having respective inputs coupled one to each of the separate outputs, having a select input and having an output to provide the output video signal; and
a decision module for generating a select signal as a function of the information, the select signal being applied to the select input in order to switch the output between the separate outputs according to the video format of the video signal.
3. A method of automatically switching between analog and digital video input paths in a video test and measurement instrument comprising the steps of:
coupling an input of the analog video input path to a video input port;
coupling an input of the digital video input path to the video input port;
coupling inputs of a video switch to respective outputs of the analog and digital video input paths; and
generating a select signal for the video switch as a function of information derived from the digital video input path to select which video input path is coupled to an output of the video switch for further processing by the video test and measurement instrument.
4. The method as recited in claim 3 further comprising the step of providing a text message on a display of the video test and measurement instrument indicative of which video input path is selected for output by the video switch.
5. The method as recited in claim 4 wherein the test message includes information about a video signal coupled to the video input port.
6. An apparatus for processing a video signal applied to an input port of a test and measurement instrument comprising:
an analog buffer having an input coupled to the input port and having an output to form an analog video input path;
a digital video receiver having an input coupled to the input port and having an output to form a digital video input path;
a video switch having inputs coupled to the respective outputs of the analog and digital video input paths; and
a decision module having as inputs information from the digital video receiver and having an output coupled to a select input of the video switch, the decision module generating a select signal at its output as a function of the information to select which video input path output is provided at the output of the video switch.
7. The apparatus as recited in claim 6 wherein the information includes one or more of a lock signal, a carrier detect signal and a video standard signal.
8. The apparatus as recited in claim 7 wherein the decision module generates the select signal as a function of the lock signal.
9. The apparatus as recited in claim 7 wherein the decision module generates the select signal as a function of the carrier detect signal.
10. The apparatus as recited in claim 7 wherein the decision module generates the select signal as a function of the lock and carrier detect signals.
11. The apparatus as recited in claim 7 wherein the decision module generates the select signal as a function of the video standard and lock signals.