Is the Raspberry Pi capable to pass audio from an input to an output, visualizing along the way?

Question

I'm looking to place a Raspberry Pi in between an audio input and speakers, visualizing LEDs along the way.

My first question is simple: Is the Raspberry Pi capable of taking an audio input and passing it through the Pi to output it without lag? (3.5mm jack -> USB Soundcard -> Raspberry Pi -> USB Speakers or 3.5mm out if needed.) The lack of latency is important as it will need to sync with video. Is this possible?

Second question is a little more complicated. Is the Raspberry Pi (any version) powerful enough to analyse the audio input and visualize the audio in realtime, (via LEDs) to then output the audio without any latency? If the answer is no, is the latency caused by passing the audio through the board, or is it because of the visualization? If so, I could always just split the audio going to the speakers and the audio going to the Pi, thus negating the need for an output from the Pi.

Answer 1

You don't need to pass audio through the Pi. You just need to "tap off" the audio into the Pi to generate the visual you are looking for. What you can do is use an op-amp to follow the audio signal and buffer it into the audio input of the the Pi.

As far as latency goes, there will always be some latency associated with digital signal processing. I don't think it will be hugely noticeable if the code is lightweight enough. 10-20 milliseconds I think is achievable.