[mythtv-users] Occasional 376 B recordings from Ceton card

Ronald Frazier ron at ronfrazier.net
Tue Oct 18 11:11:06 UTC 2011

On Sun, Oct 16, 2011 at 2:15 AM, Erik Jensen
<eriksjunk at laurelwoodart.com> wrote:
> I am running 0.24-fixes with the latest Ceton patch, and I am getting
> occasional 376 byte recordings. Sometimes it only causes me to miss
> the one recording, but other times the backend completely stops
> working until I notice and restart it, causing it to miss several
> recordings. During the time it is non-responsive, there is constant
> activity on the recording drive. Any ideas what the problem could be?

Are you positive this is a channel that works and is marked Copy
Freely? Can you view this channel with myth using livetv? Or how about
when feeding the video directly into mplayer using the instructions on
ceton's website:

Assuming the channel is otherwise fine, 376 bytes is exactly the size
of 2 mpeg-ts packets. I'm guessing those packets are a PAT and a PMT.
It sounds like the Ceton card is feeding enough data for myth to get
the PAT/PMT but nothing more. I'm thinking it's a case of the channel
being CCI restricted. My cable provider doesn't actually restrict
anything in the package I subscribe to, so I have no idea how the card
behaves when that happens, but it seems like a likely scenario. Even
if the channel is normally viewable, it could be a case of a temporary
CCI restriction on the channel. Although CCI flags are typically set
on a per-channel basis, they can in theory change from program to
program. I don't know of any providers that do that, but it's
possible. Another possibility is that the CCI flags are temporarily
disappearing, and a CGMS flag is going into effect in it's absence. I
know I've seen this happen a few times, and I've no idea why. When
running my CCI scanner tool, it would come across a channel marked
with Copy Generation Management System - Analog: "One Copy" (0x02),
but then when I'd recheck the channel a minute later, it would by back
to Copy Control Information: "Copy Free" (00).

If you can't figure out anything, you could try emailing me the 376
byte recording and I can take a peek at it. Also try sending me a copy
of the myth backend log (please strip it down so that it only covers a
couple minutes before and after the recording was scheduled to start).
However, in order for this log to be useful to me, mythbackend will
need to be running with the "-v general,important,channel,record"

Ron Frazier

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