First things first, here's the H900's specification table:
|Supported video formats||NTSC, PAL, SECAM|
|Video controller||All-in-One Conexant CX23418 10-bits hardware MPEG-2 encoder with
3D adaptive comb filter for NTSC and video/audio broadcasting decoder.
|3D Y/C separation||Supports NTSC video signal 3D Y/C separation|
|Resolutions||720*480(full D1) / 640*480 / 640*288 / 640*240 / 352*480(Half D1) /
352*288 / 352*240(SIF) / 320*240 / 240*180 / 240*176 / 176*144 / 160*120
|Video compression||ISO/IEC 13818-2 (MPEG-2)
ISO/IEC 11172-2 (MPEG-1)
|Stereo format||North America and Taiwan (BTSC and SAP) Japan (EIAJ)
Europe (NICAM and A2/Dual-FM) FM(stereo) radio
|Audio ADCs||16-bit ADC converter|
|Sample rates||32KHz / 44.1KHz / 48KHz|
|External||TV cable/antenna input
FM Radio Input
9-pin Mini-DIN Connector (S-video, Composite video input,
Stereo audio input/output )
|Internal||Power switch connector (2-pin x 2, white )
enable/disable power up jumper
A digital television broadcast is already in the form of a digital video stream when it hits your aerial. However, unsurprisingly, an analogue signal isn't, so the analogue signal must be decoded and then encoded into a digital stream for the PC to make use of. The encoding can be done in software, but in the case of the Compro H900, the on-board Conexant chip deals with turning the analogue signal into a digital MPEG-2 stream, saving the CPU the hassle.
The usability of an analogue TV tuner is at risk due to the analogue broadcast turn-off in a few years' time. That said, a few years in PC terms is a lifetime, so the two real limiting factors on such a TV tuner are image quality and channel choice, really.
Still, cast your eyes towards the bottom of the spec. table and you'll see internal connections for the 'power switch'. Interesting, eh? We'll get to those shortly.