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

[D Richard Felker III]

On Wed, Apr 09, 2003 at 08:16:42PM -0400, Christopher Caldwell wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Greetings,
> 
> 3 questions, perhaps related:
> 
> 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.

> 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.)

> 3:  When playing .avi files that are being recorded,
>   I cannot skip around because the indices haven't
>   been built yet.  That is:
>        streamer -o afile.avi -F stereo &
>        mplayer -idx afile.avi -quiet
>   allows me to see the file coming in, but I can't
>   "rewind" it or skip around when viewing it.
>   Am I confused?  Is this unfixable without
>   postprocessing the file prior to running mplayer
>   on it?
> 
>   It should at least be possible to skip around
>   in places that have been previously seen, as
>   the indices could be in memory, no?

Try -forceidx, perhaps. You should be able to seek up to the part that
was recorded when mplayer started. Beyond that, you can't seek.

Rich