[MPlayer-users] .wav files, speed and seeking in avi files

Christopher Caldwell caldwell_christopher at hotmail.com
Thu Apr 10 04:21:59 CEST 2003


>From: D Richard Felker III <dalias at aerifal.cx>
>Subject: Re: [MPlayer-users] .wav files, speed and > 1:  Is it possible to 
>play Microsoft .wav files
> >   from a pipe?  That is,
> >        mplayer - < somefile.wav
> >   works but
> >        (cat somefile.wav; sleep 100) | mplayer -
> >   fails, claiming that it doesn't recognize the
> >   file format.  The latter does work with other
> >   file formats (such as Vorbis, AVI files, etc)
>That's because these two commands do entirely >different things. One 
>creates a pipe, the other
>opens a (fully seekable) file on stdin.

>Try with -cache 4096 or so, or else use
>-demuxer 17 to tell mplayer it's audio so it
>doesn't have to detect.

-demuxer 17 fixes my problem (thanks!).  However,
it doesn't explain why other data types (such as
Vorbis) work.  The only thing I can think is that
the audio analysis in demux_audio.c does some sort
of seek that fails and vorbis does not.  In any
case, I have my workaround.  Again, thanks.
> > 2:  I seem to be able to set the speed of audio
> >   playback with -speed, but it has no noticable
> >   effect on the video.  Is this expected?  It
> >   would be really nice if I could set the speed
> >   interactively (and go backwards!)
>Playing most movie files backwards is not possible. (Unless you want
>to decode all the way from the last keyframe, which would mean less
>than 0.5 fps, or cache all the decoded frames in memory.)

This must be file type dependent (i.e. a problem
with avi files).  Is there a better movie protocol
to be using?  So far, avi files:

1:   Don't work when they get really big
2:   Tend to be indexed after they are completed

TiVo and Instant Replays are both able to record
and skip around (or fast forward or backward)
while recording.  Any guesses how we can get to
that point?

Thanks!  --Chris

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