As jexx says, you can't take an analogue (red or black jack) or digital (orange jack) output and connect to a video input (yellow jack) and expect anything sensible to come out.
If what you mean is can I connect a CD player to the audio DVD inputs, then yes. By audio, I mean the stereo analogue or the digital output of the CD player which could go into the receiver where it is marked DVD or CD or whatever. The limitation is with a turntable which has different gain requirements. All other sources have the same 'line level' outputs.
Some processors also allow you to show video from one source while hearing audio from another source. This is handy if you have a quality tuner and want to use the output from that when watching a TV simulcast. However, not all receivers will do this! You'd have to check your receiver manual for this.