[mythtv-users] Help needed - initial setup questions RE: SA3250 and firewire

David Madsen david.madsen at gmail.com
Tue Jun 14 23:13:39 UTC 2005

> My questions:
> 1. I have a Scientific Atlanta SA3250 with enabled
> firewire ports.  Is mythTV support for automatic
> recording of HD and SD channels through the firewire
> port completely nailed down, or is it still
> experimental or buggy ?

I also have a SA3250 that I use for recording, and from my experience
they setup still has much to be desired from a stability standpoint. 
This isn't MythTV's fault per say since that side of things works
reliably.  The problems I run into is that occasionally the cable box
will get "confused" and for some reason will think that channels that
do not have any copy protection flags set are "copy once" material and
will refuse to broadcast it over the firewire bus.

Unrelated to the first issue, the cable box also seems to be touchy
about how the plugs are handled.  To get my box to reliably broadcast
the video stream I had to manually increment the n_p2p_connections in
the oPCR on the cable box so that it would toggle between 1 and 2 when
MythTV began recording instead of 0 and 1.  It seeems that when the
box tries to start and stop the stream (the 0 and 1 case) it doesn't
always start back up when Myth tries to start recording.  The odd
thing is that in the prior releases of libraw1394 with the old
isochronous API this quirk was not present.  It only happens when
using the newer (and better) API.

If there are any experts in the house that have seen and solved either
of these problems I'd love to know!  I have exhausted my ideas on how
to fix these quirks.

> 2. Since I don't get analog only channels through the
> firewire port, will mythTV support both a firewire
> input (for the digital SD and HD channels) and a
> Hauppage PVR-350 for the analog channels ?  If so,
> will I have to run two seperate guides, or can you
> tell it "this tuner only gets these channels, and this
> tuner only gets those channels" ?

I do this currently with my setup since my cable company broadcasts
the basic channels over analog as well.  I have found it best to
create two lineups with your zap2it login, each with the correct
channels for each individual tuner.  Then when setting up the tuners
in Myth you can point each tuner to the correct zap2it lineup.

> 3. I think my SA3250 will have more than one firewire
> port - can I plug two of them into my server and
> record two simultanous SD shows ?  With my PVR-350,
> that would be 3 total tuners, right ?

Your assumption here is incorrect.  There are 2 firewire ports on the
cable box, but there is not 2 tuners in the box to use individually. 
The 2nd port can be used to connect other 1394 devices onto the same
bus, but not to record a 2nd show from the same cable box.  In my case
I have my PC plugged into one port, and the other connects to the
firewire input on my TV.

> 4. Since I will not be using my mythTV system to watch
> video or playback in any way, is there any drawback to
> running mythTV on this system under freeBSD ?  I
> figure since file I/O is essentially all I am doing,
> that there wont be any drawbacks or loss of
> functionality by using freebsd instead of linux.

I can't personally speak to this since I don't have experience trying
to run MythTV on freeBSD.

> 5. Will mythTV + SA3250 + working firewire allow me to
> change channels over firewire when recording off of
> it?  I really want to not do the lame IR dongle hack

You will not be able to change channels on the SA3250 over the
firewire bus.  This box does not currently have any support for doing
like the Motorola ones do.  You will have to do the IR Blaster route. 
I built a simple blaster and have had success changing channels, but
occasionally the box drops some numbers causing my recordings to fail
since the box is not tuned to the correct channel when this happens. 
If any IR Blaster experts have any ideas on how to improve the
reliability of these things I'd love to hear your ideas. :)

I hope this info will be of use to you as you plan your setup!

--Dave Madsen

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