[linux-dvb] Re: Software playback (again)

[Dave Chapman <dave@dchapman.com>]

On Tuesday 04 September 2001 11:09 pm, you wrote:
> Hi,
>
> > The following _should_ work in theory, but doesn't in practice:
> >
> > dumprtp | ts2ps APID VPID | mplayer -
> >
> > This gives very "jumpy" playback and lots of "libmpeg2" errors.
>
> jumpy picture is ok, as mplayer has no input media caching code yet.
> you may try TOOLS/cache.c, piping data through it. it was made for
> playback over nfs/samba network, but should work for such pipes too.
> there is also new code TOOLS/cache2.c, it will be integrated to mplayer,
> but it needs some structural chanegs in steraming layer first.

I've tried both cache and cache2.  cache "works", but makes no difference, 
and cache2 doesn't seem to output any data.  I've only tried them quickly 
though.

I had more luck with "buffer".  This removes the "libmpeg2" errors, and I get 
almost perfect replay.  However, there are still jumps every second or two.

This is using the commandline "buffer -p 90".

>
> but libmpeg2 errors are strange, it happens only if video stream is
> damaged! maybe my mpeg demuxer is broken, and it doesn't handle the case if
> read() actually reads less bytes than requested. i'll check this.
> (btw it worked with http streaming of mpeg files)

The exact error is:

@@@ libmpeg2 returned from sig11... (bad file?) @@@

I am also getting the message "Your system is too SLOW to play this!".

This is only when I am not using any buffers in my pipestream.  Using a 
buffer fixes both of these errors.

>
> > Has anyone actually managed to get a software player to perform good
> > quality, _synchronised_ playback?
>
> you can correct a-v desync with + - keys in mplayer (0.1s steps), or -delay
> commandline option. it shouldn't happen except when your soundcard driver
> reports buffer status (ioctl GET_ODELAY) wrong.

I should RTFM :-)  There always seems a constant "error" on my system, so I 
would guess that this is the problem.

> I made my own ts2ps converter some months ago, and it was planned to
> include into mplayer, but i forget. I'll recheck and integrate.

That would be very useful.  How do you handle identifying the audio and video 
streams?  Do you require a PAT/PMT in the TS, do you detect them 
automatically from the stream (i.e. detect the first video and audio streams 
in the stream), or does the user have to specify them?  Ideally, it would be 
nice if you could support all three, but always give the user the chance to 
specify them manually.

MPlayer is now getting very close to a working "off the shelf" solution for 
DVB software playback.  

Thanks,

Dave.


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