Mailing List Archive

Strange issues with MPEG channels on QAM
I've got an HDHomeRun connected to Comcast (QAM-256), which I use to
record both my local ATSC stations and some of my favorite basic cable
channels. The problem is that on the non-ATSC channels the front end
seems to barf on occasion, resulting in black screens, a black & grey
screen with audio (left 1/3 or so is solid gray, right 2/3 solid black),
randomly morphing program lengths (an hour program might show up as 0:55
or 1:08), and seemingly random commercial skipping.

The problem areas seem to occur where Comcast has inserted local
advertisements in the stream. When they occur Myth seems to lose sync
with the stream. When this happens the front end spits out thousands of
lines like this:

[mpeg2video @ 0x108ba24]get_buffer() failed (stride changed)

Sometimes it recovers, sometimes it aborts back to the recording screen,
and on occasion it just crashes.

Has anyone else seen this? I checked Google and Trac and couldn't find
any other mention of this. I'm running SVN 12770 but this has been
happening ever since I started recording these channels many many SVN
revisions ago.

--
Joshua M Thompson <funaho@jurai.org>

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Re: Strange issues with MPEG channels on QAM [ In reply to ]
On Sun, 2007-02-11 at 01:51 -0500, Joshua M Thompson wrote:
> The problem areas seem to occur where Comcast has inserted local
> advertisements in the stream. When they occur Myth seems to lose sync
> with the stream. When this happens the front end spits out thousands of
> lines like this:
>
> [mpeg2video @ 0x108ba24]get_buffer() failed (stride changed)
>
> Sometimes it recovers, sometimes it aborts back to the recording screen,
> and on occasion it just crashes.
>
> Has anyone else seen this? I checked Google and Trac and couldn't find
> any other mention of this. I'm running SVN 12770 but this has been
> happening ever since I started recording these channels many many SVN
> revisions ago.

I've seen this. It happened in a strangely encoded movie
I recorded a few weeks ago. And it happened when switching
from the cable company add back to the network stream.

I kept the recording, but I haven't had a chance to look at
it yet. My guess is that there is an aspect ratio or resolution
change we don't handle for some reason.

-- Daniel

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Re: Strange issues with MPEG channels on QAM [ In reply to ]
On 2/12/07, Daniel Kristjansson <danielk@cuymedia.net> wrote:
> On Sun, 2007-02-11 at 01:51 -0500, Joshua M Thompson wrote:
> > The problem areas seem to occur where Comcast has inserted local
> > advertisements in the stream. When they occur Myth seems to lose sync
> > with the stream. When this happens the front end spits out thousands of
> > lines like this:
> >
> > [mpeg2video @ 0x108ba24]get_buffer() failed (stride changed)
> >
> > Sometimes it recovers, sometimes it aborts back to the recording screen,
> > and on occasion it just crashes.
> >
> > Has anyone else seen this? I checked Google and Trac and couldn't find
> > any other mention of this. I'm running SVN 12770 but this has been
> > happening ever since I started recording these channels many many SVN
> > revisions ago.
>
> I've seen this. It happened in a strangely encoded movie
> I recorded a few weeks ago. And it happened when switching
> from the cable company add back to the network stream.
>
> I kept the recording, but I haven't had a chance to look at
> it yet. My guess is that there is an aspect ratio or resolution
> change we don't handle for some reason.

I hate to revive such an old thread but I couldn't find a more recent
one referencing this problem. I just started seeing this problem on
comcast as well, also around some commercial breaks. My recordings
are off of a HDTV5500 card though not the HDHomeRun. It causes the
frontend to crash during playback, it looks like the same errors are
get generated on the backend during commflagging but it doesn't cause
the commflag to crash. What would be helpful for troubleshooting
this?
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Re: Strange issues with MPEG channels on QAM [ In reply to ]
On Mon, 2007-07-09 at 07:38 -0700, Asher wrote:
> On 2/12/07, Daniel Kristjansson <danielk@cuymedia.net> wrote:
> > On Sun, 2007-02-11 at 01:51 -0500, Joshua M Thompson wrote:
> > > The problem areas seem to occur where Comcast has inserted local
> > > advertisements in the stream. When they occur Myth seems to lose sync
> > > with the stream. When this happens the front end spits out thousands of
> > > lines like this:
> > >
> > > [mpeg2video @ 0x108ba24]get_buffer() failed (stride changed)
> > >
> > > Sometimes it recovers, sometimes it aborts back to the recording screen,
> > > and on occasion it just crashes.
> > >

> I just started seeing this problem on
> comcast as well, also around some commercial breaks. My recordings
> are off of a HDTV5500 card though not the HDHomeRun. It causes the
> frontend to crash during playback, it looks like the same errors are
> get generated on the backend during commflagging but it doesn't cause
> the commflag to crash. What would be helpful for troubleshooting
> this?

If you can reproduce the crash with the latest SVN trunk,
please create a backtrace using the instructions in the
MythTV documentation. Then create a new ticket with the
problem description and attach the backtrace to the ticket,
we may a small sample of the video as well, so please don't
delete it.

-- Daniel

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Re: Strange issues with MPEG channels on QAM [ In reply to ]
On 7/9/07, Daniel Kristjansson <danielk@cuymedia.net> wrote:
> On Mon, 2007-07-09 at 07:38 -0700, Asher wrote:
> > On 2/12/07, Daniel Kristjansson <danielk@cuymedia.net> wrote:
> > > On Sun, 2007-02-11 at 01:51 -0500, Joshua M Thompson wrote:
> > > > The problem areas seem to occur where Comcast has inserted local
> > > > advertisements in the stream. When they occur Myth seems to lose sync
> > > > with the stream. When this happens the front end spits out thousands of
> > > > lines like this:
> > > >
> > > > [mpeg2video @ 0x108ba24]get_buffer() failed (stride changed)
> > > >
> > > > Sometimes it recovers, sometimes it aborts back to the recording screen,
> > > > and on occasion it just crashes.
> > > >
>
> > I just started seeing this problem on
> > comcast as well, also around some commercial breaks. My recordings
> > are off of a HDTV5500 card though not the HDHomeRun. It causes the
> > frontend to crash during playback, it looks like the same errors are
> > get generated on the backend during commflagging but it doesn't cause
> > the commflag to crash. What would be helpful for troubleshooting
> > this?
>
> If you can reproduce the crash with the latest SVN trunk,
> please create a backtrace using the instructions in the
> MythTV documentation. Then create a new ticket with the
> problem description and attach the backtrace to the ticket,
> we may a small sample of the video as well, so please don't
> delete it.
>
> -- Daniel

Yep this is all with the latest svn trunk (as well as the -vid branch)
I will try to generate a good backtrace and open a ticket. I've had
problems generating useful backtraces before so let me know if it is
incomplete
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Re: Strange issues with MPEG channels on QAM [ In reply to ]
On 7/9/07, Daniel Kristjansson <danielk@cuymedia.net> wrote:
> If you can reproduce the crash with the latest SVN trunk,
> please create a backtrace using the instructions in the
> MythTV documentation. Then create a new ticket with the
> problem description and attach the backtrace to the ticket,
> we may a small sample of the video as well, so please don't
> delete it.

I created a ticket for it: http://svn.mythtv.org/trac/ticket/3710

I have the -v all log but it is too large to attach would a different
log be more helpful -v playback ?
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