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| Processing AV video signal |
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| Benta:
OK, to be more detailed: 1: AC couple the video signal. 2: place a quality analog switch (eg, DG419B) between the AC coupled CVBS signal and ground (or some reference voltage depending on the voltage shift you need). 3: control the analog switch from the CSOUT output from the LM1881. This will clamp your sync pulses to ground/reference and thus DC shift your CVBS signal. You'll need a video buffer after this circuit, eg, LM6171. Also, you'll probably need to increase impedance before the switch, I don't know your video source. |
| syntax333:
I tried to explain in figure. Basically,A signal obtained from HDMI to AV converter is fed to Bias tee circuit. In bias tee I am shifting the signal at a certain DC level. After that in order to send the AV signal to AV to HDMI converter I have to get the original signal without the DC shift. That is why I am trying to get the original signal because I will feed the signal to AV to HDMI converter. |
| Benta:
--- Quote from: soldar on December 22, 2018, 04:29:03 pm ---I don't understand. Why do you want to reconstruct the original signal? Why don't you just use the original signal? --- End quote --- Bias tee is a normal way of combining RF or video signals with DC, for instance to remotely supply an antenna amp with power through the coax. DC shifting CVBS signals is done all the time, in a VCR or TV perhaps 20 times in the complete circuit. Nothing special about this. |
| Benta:
--- Quote from: syntax333 on December 22, 2018, 04:49:49 pm ---I tried to explain in figure. Basically,A signal obtained from HDMI to AV converter is fed to Bias tee circuit. In bias tee I am shifting the signal at a certain DC level. After that in order to send the AV signal to AV to HDMI converter I have to get the original signal without the DC shift. That is why I am trying to get the original signal because I will feed the signal to AV to HDMI converter. --- End quote --- Syntax333, are you sure that the CVBS-to-HDMI converter isn't AC coupled already? That would make this whole thing unnecessary. |
| syntax333:
:palm: good point. I will check that first. |
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