[MPlayer-dev-eng] video pipes

Thomas Comiotto comiotto at rcfmedia.ch
Tue Mar 23 00:03:42 CET 2004


I'm trying to put together a small video broadcasting solution with mplayer as 
playlist-based player and pdp as realtime video mixing component. Therefore I 
need a way to pipe a/v from mplayer to pd. I am well aware that currently 
there's no standardized solution to this problem (except of the 
vloopback-hack or buying one capture card per channel and routing a/v via 
hardware ports - unfortunately I can't afford that) but nevertheless I need 
to come up with a solution. Before I start hacking on an output filter that 
fits my needs I wanted to ask you to run your checks on what I possibly would 
come up with - maybe there's a solution that I didn't think about yet or what 
I plan to do is just plain bullshit, you never know...

Disclaimer: I am _very_ new to video programming, but basically have rather 
decent programming skills.

Hacks (video):
PDP can read raw video data from a FIFO pipe. Currently the supported formats 
V12 yuv data : [type bitmap/yv12/320x240]
rgb data : [type bitmap/rgb/320x240]

I ran a quick test with mplayer's -vo yuv4mpeg filter and the named pipe 
approach sort of works, but besides a jittering audio channel because of 
having mplayer waiting for pdp to pull the last frame of the stack before 
pushing the next one to the stack I loose mplayer's seeking/transport 
functionality when using this -vo filter. Of course we still want to be able 
to do basic transport functions in the player. Is there a way of using 
multiple output filters simultanously, feeding a pipe in the background while 
still displaying an x-window and do seeking and the like?

What alternatives to the named pipe approach or possibly streaming locally via 
udp/rtp (too expensive) do I have? Does anyone of you have some deeper 
insights in what the status of exchanging video data between *nix apps is at 
the moment?

There seems to be no jack output module for mplayer available. Is anyone 
working on that or would this also have to be done for piping the audio data 
to pd?

I hope someone can give me some hints on solving this one...

Best regards,

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