How to implement audio input and output on Raspberry Pi

The following answer does not answer the question. Actually, I'm quite curious about this matter.

If you think about it, the audio output can be through the 3.5 port or through HDMI. But there is no way to input audio. It seems that there is no mouth for this recording. The one next to it is the AV output port.

The stupidest way I came up with was to connect a USB sound card. You can record.

I have a USB recording device on my camera head. This is doable. I also checked online and found that others use it this way. Use the USB microphone on the camera.