[mythtv-users] Analog firewire recordings end early due to 25% fewer frames

Yeechang Lee ylee at pobox.com
Wed Feb 4 04:45:43 UTC 2009

Sam Logen <starz909 at yahoo.com> says:
> Hi, not sure if others answered your issue.  I'm assuming that by
> 'analog' that you mean the analog channels under 100, and that
> you're not capturing through the a/v ports of the dct unit.

Correct. As my subject line indicates, I'm talking about FireWire as
the delivery path from the cable box to the backend in all cases,
whether involving analog channels (that is, channels delivered via
analog signals from the cable company to the cable box) or digital
(channels delivered via digital signals from company to box.)

(I feel silly, spelling this out so explicitly, but at least one
developer basically reacted to my initial message with the equivalent
after [clearly not fully] reading my original message. You know who
you are.)

> Do you have all your dct6200's up and running at once? And if so, do
> they all have the same degraded quality?

Yes and yes. As I noted, the isue exists on both boxes.

> I've learned that over time, coax connections in a house can
> degrade, so I'd have someone from your cable company come out and
> test the signal.

Signal's fine; I got it tested when a cable company technician came
out to replace my boxes right after this issue first appeared in
September 1997.

> Though if your cable company is voluntarily cutting framerates out
> of your analog channels, I suppose all you can do is file a
> complaint.

I'm 99% certain it wouldn't do any good. Although the diminished
picture quality from the removing of 25% of frames is indeed visible
via the component jacks, analog channels' picture quality is already
low enough that the difference is marginal. Besides, the company
would've cut the bandwidth on the analog channels only to gain the
necessary bandwidth for more (digital) channels; there surely isn't
any excess bandwidth to give back, if you will, to restore analog
channels' quality.

I wouldn't want my cable provider to take that road, anyway; I'd much
prefer the company get rid of analog channels completely (as it sounds
like what Comcast is doing here in the Bay area, as a contemporary
thread indicates) as the visual quality of digital channels, even the
non-HD ones, is far superior. I'd kill for Turner Classic Movies in
digital, even if still in SD. (Yes, I know there are lucky people
whose providers do carry TCM in digital format.)

> It's possible that a low signal from these channels could be
> destabilizing your firewire connection.  Do you have to re-prime it
> afterwards?

Yes; in fact, I do.

Your question got me thinking, and I'm going to start a new thread on
a related topic.

Frontend:		P4 3.0GHz, 1.5TB software RAID 5 array
Backend:		Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs:		Four high-definition over FireWire/OTA
Accessories:		47" 1080p LCD, 5.1 digital, and MX-600

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