CAS is really a nightmarish format that really should not exist. Many of the CoCo/Dragon emulators patch the ROMs to emulate the cassette, resulting in a format that cannot be directly mapped to a waveform, but ends up in practice requires either partaking in the same hacks, or some processing step to essentially simulate the result of patching the ROMs.

At least this is what I remember when I first started working on the CoCo stuff two decades ago.