I'm having a hard time trying to understand some basic sound engineering concepts.
Paula has four DMA-driven 8-bit PCM sample sound channels. Two sound channels are mixed into the left audio output, and the other two are mixed into the right output, producing stereo audio output. The only supported hardware sample format is signed linear 8-bit two's complement. Each sound channel has an independent frequency and a 6-bit volume control (64 levels). Internally, the audio hardware is implemented by four state machines, each having eight different states.
How can these 4 input channels be translated into the modern DSP world? The only reference I can find when trying to google some modern DACs, is that they can support > 2 output channels (5.1 sound and so on). From what I understand, today the mixing is mostly done in software, and the combined result is then fed to the CODEC/DAC. Are there any analog mixer chips with multichannel support and how would they work?