[mythtv-commits] Ticket #4891: Enabling VBI for a broader array of drivers and hardware
MythTV
mythtv at cvs.mythtv.org
Fri Mar 7 23:45:34 UTC 2008
#4891: Enabling VBI for a broader array of drivers and hardware
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Reporter: starz909 at yahoo.com | Owner: ijr
Type: defect | Status: new
Priority: minor | Milestone: 0.21
Component: mythtv | Version: 0.21-fixes
Severity: low | Mlocked: 0
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Hello everyone,
Currently, the ability to view closed captioning in channels or recordings
is highly dependent on the drivers for the recording hardware. With
software encoders, this isn't a problem because mythtv offers a dialog box
to specify the location of the vbi device node. With hardware encoders,
even the common Hauppauge encoders, mythtv relies on the drivers being
able to insert vbi data into the mpeg stream, where mythtv will find the
data and display it, if the user requests it.
Unfortunately though, few hardware drivers do this well, and some
developers choose not to add this feature to their driver code. The
popular ivtv driver only does this well for some hardware, and, for
example, a developer of v4l's blackbird driver, Michael Krufky, has
decided not to implement this feature in the blackbird drivers.
Why? Because the driver, and other similar drivers like ivtv, create a
dedicated vbi device node as well, which gives the computer access to the
vbi data streaming from the hardware. In Krufky's and my own opinion,
this would be a more convenient and stable means of acquiring vbi data for
broadcasts.
http://lists.zerezo.com/video4linux/msg20539.html
If mythtv claims it supports decoding CC, which it must since there are
menus that allow it to be enabled and configured, then I think it would be
more efficient for mythtv to give the user the option of specifying where
the vbi data is to be captured -- the mpeg stream, or a dedicated device
node.
I was considering an option that is placed in the mythtv-setup menu, under
configuring a new hardware encoder card, and when enabled, lets the user
specify a location for a vbi device node, and perhaps a slider or box to
input a delay or buffer number if the vbi device node is not synched
properly with the mpeg node.
I'm not sure how this external vbi data will be recorded with the video
nuv file; whether the vbi data should be a separate file linked somehow to
the video file, either with the same name or through the database, or if
the vbi data should be inside the nuv file, in which case, I'm not sure if
a lossless transcoding process will be necessary.
I consider this a workaround or bug fix, and not a feature request,
because mythtv is supposed to already decode cc; this is just a means of
letting it work for a wider range of devices whose drivers do not, and
perhaps will not support slicing vbi data into their mpeg stream - but do
provide a functional vbi device node.
Thank you for your patience and for considering this request,
Sam
PS. Unfortunately, I do not have programming skills sufficient for this
kind of modification, so I cannot propose a patch, but I am willing to
help with testing on my free time.
--
Ticket URL: <http://svn.mythtv.org/trac/ticket/4891>
MythTV <http://svn.mythtv.org/trac>
MythTV
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