[mythtv-users] Capture card luminance bandwidth (BT8xx and PVR-250)

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 
> know.
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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