[nSLUG] mplayer FYI: undocumented option to -tv

Mike mspencer at tallships.ca
Tue Nov 28 19:19:52 AST 2006


Of interest only to mplayer users:

Nobody has asked about this.  I was about to do so, after much
grovelling and googling, when I finally stumbled over the answer by
guesswork.

Some TV capture cards have more than one input plug -- composite,
S-video and/or (I don't know the technical name) "Television".

With all suitable drivers running and working, mplayer detects all
three possible inputs and chooses whatever it sees as the "first"
one. If the input you're using is one of the others, mplayer sends a
stream of meaningless data to the display.

The mplayer docs don't mention this and there is no documented way to
specify or force the choice of one of the inputs, although the startup
messages to stdout catalog the available inputs and report which
of them mplayer is choosing.

Fix is to use an undocumented option to the -tv switch:

  mplayer tv:// -tv driver=v4l:input=n:other:options:here -other_switches
                               |||||||
  -----------------------------+++++++


where n is an integer determined by reading the startup messages
provided by mplayer.

In my case, running mplayer without the input= option to -tv resulted in:

      Playing tv://.
      TV detected! ;-)
      Selected driver: v4l
       name: Video 4 Linux input
       author: Alex Beregszaszi
       comment: under development
      Selected device: bttv video
       Capabilites: capture tuner overlay clipping frameram scales
       Device type: 235
       Supported sizes: 48x32 => 768x480
>>>>   Inputs: 3
        0: Television: tuner audio tv camera  (tuner:1, norm:ntsc)
        1: Composite1: audio camera  (tuner:0, norm:ntsc)
        2: S-Video: audio camera  (tuner:0, norm:ntsc)
>>>>  Using input 'Television'

But my input was composite so all I was getting was pixel garbage or a
blank TV window.  Adding the input=1 option to the -tv switch fixed it
right up.

Ho-hum.

FWIW,
- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^



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