[pvrusb2] Intermittent video stream damage

[Carsten Meier]

Am Sun, 14 Dec 2008 13:40:40 -0600 (CST)
schrieb Mike Isely <isely at isely.net>:

> However the symptoms you are describing don't quite match that.  I
> never saw messages about "damaged" data :-( For what it's worth, the
> pvrusb2 driver passes the byte stream through unmolested from the
> hardware, and that area of code is completely within the pvrub2
> driver and has been stable for several years now.  The only time the
> driver does anything with the data is right at stream startup - it
> throws away bytes from the driver until it sees a valid marker for a
> packet header.  Some PVR-USB2 devices have had a tendency to spew
> garbage before valid data right at startup, probably the result of an
> uninitialized video buffer, and this could confuse some apps like
> xawtv.
> 
> I suppose if something were causing capture issues upstream of the
> mpeg encoder, like loss of video sync, then the encoder could get
> confused and start spewing bad frames.  I saw the other reply from
> Carsten suggesting the problem cleared for him after moving to a
> different V4l-DVB core version.  You're running a 29xxx device,
> right?  That means the video capture chip in the saa7115 which is
> less common these days. The cx25840 seems to be what recent devices
> (including the 24xxx model) use for video capture.  So breakage in
> the saa7115 chip-level driver in V4L-DVB might have gone unnoticed
> for a while :-(
> 
>   -Mike
> 

This is not an mplayer issue. It happens in MythTV which always
writes the stream to disk first. My device is a 24xxx (as told by the
white sticker). However, after updating the v4l-core this error didn't
occur any more. The loss of video sync is also very unlikely to be the
cause. The device is connected to analog-cable TV and reception
conditions are perfect. I'll try to supply a bad stream if it
should happen again.

Regards,
Carsten