[mythtv-users] Capture card luminance bandwidth (BT8xx
Gert van der Knokke
gertk at xs4all.nl
Sat Dec 4 15:44:55 UTC 2004
Cory Papenfuss wrote:
> I had heard that the TV cards need a pretty strong signal. I'd
> believe it given the RF-toxic environment inside a PC's case. Good to
Since the tuner modules used on the capture cards are the same as used
in any TV or VCR it should not behave different.
However you mentioned RF-toxic environment *inside* the PC-case, it is
even worse: A PC is never shielded 100% (holes everywhere) so even
outside the case there are RF signals which can interfere with your
cable or antenna signal. Most of these problems are due to the very poor
quality coax which is out on the market (esp. in ready made cables). By
using double shielded coax (e.g. Hirschmann KOKA) and full-metal
connectors you will find that the picture captured by your card is much
better. Also make sure that your PC is properly grounded.
On the topic of the number of lines captured: I can't imagine how a
capture card can capture fewer lines than there are transmitted. What
does it do ? Repeat the prevous line ? Is the card capturing a complete
frame (which seems logical for the MPEG2 encoder to process) or just one
line at the time ?
If it is capturing a completer frame all lines should be present, nicely
'clocked' in by the Horizontal Sync pulse.
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