Efectivamente youtube no te vale. Prueba aquí:

2D Demo Trailers (HD)

En concreto:
DTS HD-Master Audio Sound Check 5.1 (Lossless)
DTS HD-Master Audio Sound Check 7.1 (Lossless)
Dolby Digital Plus Channel Check (Lossless)
Dolby TrueHD Channel Check (Lossless)