[mythtvnz] Good DVB-T USB capture device

[Pshem Kowalczyk]

Hi,


On 23 April 2010 13:41, Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:

{cut}
>
> It is extremely unlikely that a reception problem would affect TV One
> only and not all the other channels on the same multiplex.  A
> multiplex is just a stream of data packets with different ID numbers
> on them.  Recording one channel is done by selecting the packets with
> the right ID numbers out of that stream.  So any reception problems
> with a multiplex *must* affect all channels on that multiplex.  If
> your problem really is only affecting TV One, then it would likely be
> a playback problem with 720p files, and that should also affect TV2
> the same way.  The other channels on the TVNZ multiplex are 576p.
> Playback problems are often characterised by the problem happening in
> a different place in the file each time you play it.  Recording
> problems will always be seen in the same place if a file is played
> back multiple times.

It is a recording issue. I just simply wonder if it's possible that
the card only has issues with capturing 720p, but not 1080 or 576.


> An old rule of thumb comes to mind here.  When in doubt, suspect the
> cable.  Is it possible one of your aerial cable connections is
> intermittent?  So sometimes it is not getting enough signal to receive
> the TVNZ multiplex OK?

I was thinking about that, but there is somewhat disturbing regularity
to the issue - (like every 30mins or so) but again - TVNZ6 records
fine from the same tuner, during the same time.

> BTW When I heard about this "diversity" feature, I had a thought about
> how it might be done, and what I came up with is using both tuners
> tuned to the same multiplex at the same time, then have the software
> check for bad packets from one tuner and look and see if the same
> packet was good on the other tuner.  That is a standard way of doing
> diversity in communications channels, and normally results in a much
> lower error rate even when both channels are a bit iffy, as long as
> the two channels come via different paths (in this case, that would
> mean different aerials, preferably pointed at different transmitters
> if possible).  If it is done that way, then it is all software and
> there is no actual hardware diversity switch.

Thx for that explanation, it sheds some light onto the issue.

kind regards
Pshem