Measurement was just a guess as to the exact amount of delay. I have an A/V receiver that can toggle A/V sync lag to sync A/V depending on source output, so I tried to use my best judgement of the input lag based on that experience.
I actually found the solution after changing some Rpi config settings. To anyone else looking for a solution to slight input lag (was killing my ability to play emulators), with a Raspberry Pi 2 B model, I set the video_hard_sync to “true” and the frame rate delay to 10 (option right under the video_hard_sync option in retroarch.cfg, directory is /opt/retropie/configs/all if I remember correctly).
It should be noted that this config change didn’t exactly solve my issue – with a medium overclock at 900 Mhz and with each overclock beyond, I was getting increasing input lag. At no overclock (700 Mhz) I was lag free, but performance suffered. The final solution to the input lag issue was the config changes listed above AND overclocking to 800 Mhz. Those settings combined made for a basically perfect no lag input…making platformers/etc very playable on an LCD TV.
So it seems to come down to a combination of what type of TV you have along with overclocking and Raspberry Pi config settings as well.
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