The 12-bit format that's used for video isn't linear PCM, is it? I seem to recall (from the old Video8 format, which used that approach for its digital audio tracks) that it's a logarithmically scaled system with four bits of exponent and eight bits of mantissa, surrounded by an analog compander.
If so, then for normal consumer video purposes it's certainly adequate, but it has no pretensions to being a true high-fidelity medium, and critical listening would occasionally reveal its flaws.
--best regards