[mythtv] V4L2 bug ??

[Mike Isely]

On Wed, 2 Feb 2005, Shane Shrybman wrote:

> On Wed, 2005-02-02 at 14:59 -0500, Isaac Richards wrote:
> > On Wednesday 02 February 2005 11:29 am, myth wrote:
> > > V4l2 appears to be valid only for cx8800 capture cards and falls back to
> > > V4l for all other cards. I am using a BT878A capture card on a 2.6.8.1
> > > md kernel which does support v4l2 but  NuppelVideoRecorder is using
> > > this card via the V4l API rather than the V4l2 api. The V4l2 code in
> > > NuppelVideorecorder is using a slightly more efficient way of performing
> > > transfers (select).  A quick test, moving the brackets ( c code below)
> > > allows the v4l2 code to be used resulting in a significant speed increase.
> >
> > Last time I tested things, using the v4l2 api for bttv cards was significantly
> > less stable than using v4l.  Channel changes in particular seemed to kill
> > capture quite regularly.
> >
>
> Seems stable so far. :) Is there some sort of channel changing stress
> test that can be run? I am just flipping channels by hand now.
>

This *might* be entirely unrelated, but in early January there was a bug
in the code which caused the *front end* to crash on channel changing.
The bug was due to uninitialized data.  One characteristic was that if you
successfully flip channels once - if the uninitialized fields happened to
have been "uninitialized the right way" - then it was fine from that point
forward until you restarted the front end again (and thus hit the
uninitialized data again).

This is described in bug #181.

The situation discussed in this thread here doesn't very well match the
problem solved in bug #181.  But that problem was so rampant for me at the
the time that it basically rendered my mythbox useless; surely others must
have at least seen this.  So it may still be worth reviewing that bug
description in light of the discussion above.

  -Mike

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