[FFmpeg-user] Record N RTSP frames and average into 1 jpg? In a loop?

Carl Zwanzig cpz at tuunq.com
Mon Jul 10 20:32:57 EEST 2023

On 7/9/2023 3:46 AM, David Bernat wrote:
> As for EE solutions, all you really need is to pass the AC current through
> a full-wave rectifier before the LEDs.

Not exactly, an LED is a "negative resistance" device- the higher the 
current the lower it's resistance. They need some kind of a current limiter 
so as not to self destruct. This can be as simple as a resistor or as 
complex as an externally-controlled PWM supply (for dimming). Consumer LED 
lamps have some sort of constant-current regulator to maintain near constant 
output with variations in line voltage. This could include a high-frequency 
power supply in the higher-quality lights.

> By the way, it has been a while, but I*think*  back of the envelop
> calculation allows this:
> US AC current: 60 Hz.
> Half-Wave Rectification: 30 Hz.

Half-wave rectifying gets you 60 half cycles, full gets 120 (it "folds" the 
halves from one polarity to the other).

As I mentioned before, try some different LED lights to see if they still 
show the problem, then you'll know where to put the effort. Or try a 
different camera. Or try to pull stills from the camera instead of motion video.

In the end, no matter how much processing is done, it's still 
garbage-in/garbage-out, post-processing can't make up for missing information.



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