[vlc-devel] [patch] dshow: Don't enforce "preferred" media type upon device

Paul Sokolovsky pmiscml at gmail.com
Thu Jan 12 05:29:29 CET 2006

Hello vlc-devel,

  I own a Compro VideoMate Action Ultra TV Tuner, and trying to
capture from it using VLC's DirectShow input plugin gives me a blue
screen with kernel fault (VLC 0.8.4a and few version before).

  I traced this to dshow plugin's unconditionally enforcing so called
"preferred" (for VLC) media type upon the device. By unconditional I
mean that code blindly adds I420 type to the list of media types supported by
the device. Then it sorts the list by priority, and as I420 is the
most preferred format, this likely finishes with VLC requesting media
type never supported by the device. For some broky drivers this is fatal.

  I couldn't easily trace origin of that code (it appears to be
reformated in one of commits), but there's already workaround for the
behavior described above, employed for devices providing
MEDIATYPE_Stream data. Corresponding commit log is:

r9097 | gbazin | 2004-11-01 15:10:14 +0200 (Пн, 01 ноя 2004) | 1 line

* modules/access/dshow/dshow.cpp: don't add a prefered media type when dealing with pins which handle MEDIATYPE_Stream (for some reason the WinTV PVR doesn't really like this).

  Well, I'm a witness that not just MEDIATYPE_Stream devices dislike
this, but MEDIATYPE_Video/Audio too. So, instead of adding another
workaround, I propose to remove that code.

  The patch against SVN trunk is attached.

Thank you,

Not on the list, please cc: me.

Best regards,
 Paul                          mailto:pmiscml at gmail.com
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