Parece que esta questão foi respondida em [email protected]. A resposta:
TVout is in reference to Composite, S-Video, and (I think) Component outputs.
HDMI video is fully support on nv50-era GPUs. HDMI audio may be a bit spotty depending on which GPU you have. (lspci -nn -d 10de: should give you the info). Pre-GT215 GPUs have to get audio input via SPDIF from the sound card, and nouveau doesn't quite configure that properly - it might work, it might not. For GT215+ GPUs, HDMI audio should work fine.