[DVDnav-discuss] question regarding data coming from libdvdnav

[Nico Sabbi]

On Friday 21 November 2008 11:37:31 Sergey 'Jin' Bostandzhyan wrote:
> On Fri, Nov 21, 2008 at 10:04:18AM +0100, Nico Sabbi wrote:
> > > I can only say the time that the player is printing on the TV,
> > > as I mentioned in one of the previous posts I tried playing the
> > > stream twice. The first time it crashed after about 34 seconds
> > > (0:0:34), the second time it crashed after about 57 seconds
> > > (0:0:57).
> >
> > uhm, non-deterministic
>
> Unfortunately not...
>
> > > The last theory that I have is, that maybe it is simply "too
> > > much" for the player in terms of the overall datarate?
> >
> > I doubt it, but I still have to check this possibility.
> > If you run mencoder -of mpeg with a low muxrate you can
> > see what's the actual needed datarate
>
> mencoder did not work out for me for some reason, I generated a
> bitrate histogram using avidemux2:
> http://www.deadlock.dhs.org/jin/libdvdnav/histogram.jpeg
>
> That's probably not exactly what you were asking?

it's good enough. I see max bitrate 8200, but over what window?
It may be a problematic datarate for some player

>
> I tried:
>
> mencoder -of mpeg -oac copy -ovc copy -mpegopts muxrate=1800 -o
> /tmp/out.mpg libdvdnav.mpg
>
> I am not sure if that is correct but the output I get is:
> PACKET SIZE: 2048 bytes, deltascr: 245760
> videocodec: framecopy (720x576 24bpp fourcc=10000002)
> audiocodec: framecopy (format=2001 chans=2 rate=48000 bits=16
> B/s=96000 sample-1) Limiting audio preload to 0.4s.
> Increasing audio density to 4.
> Writing header...

1800 is far too low: muxrate is ~total bitrate + some small
overhead (~5%), of course the bitrates may present spikes,
thus the muxrate must be calculated based on the spikes

>
> And then mencoder simply hangs. The output file stays at 2048 bytes
> and I need to kill -9 mencoder to get out of this. Using MEncoder
> 1.0rc2-4.1.2.
>
> > > Btw, this leads me to another question, libdvdnav has a
> > > function called dvdnav_audio_language_select(), what exactly is
> > > it good for? This does not alter the incoming data anyway,
> > > right?
> >
> > it only alters the language selection in the DVD VM (its internal
> > state-keeping code) not in the application (infact this leads to
> > a lot of mess in -at least- mplayer)
>
> I am not using this in my code, just to be sure I commented it out
> in menus.c and reripped the mpeg - both versions of the mpeg are
> the same so I guess that was not making any difference in this
> case.
>
> I'll try keeping only one video and one audio stream and playing it
> with the DSM when I get home tonight.
>
> Kind regards,
> Jin

good luck