[linux-dvb] Re: Slowmotion with ioctl on /dev/video and a cat on /dev/dvr ?

[Marcus O.C. Metzler <mocm@convergence.de>]

Marion Krahn writes:
 > "Marcus O.C. Metzler" schrieb:
 > > 
 > > Marion Krahn writes:
 > >  > Hello,
 > >  > I have a problem with the Linux DVB-API.
 > >  > I write a TS on device /dev/ost/dvr, so this stream will be played. Is
 > >  > it possible to see this TS in slowmotion by making a ioctl
 > >  > VIDEO_SLOWMOTION on /dev/ost/video ? If not, what can I do to see the
 > >  > stream in slowmotion (only with the Linux DVB-API!)?
 > > 
 > > You can't get slow motion through /dev/ost/dvr. This device assumes
 > > that it gets the data from a realtime source like a webcast or a
 > > satellite transponder. Thats why can set filters on that incoming
 > > stream just like it came from satellite. If you want slow motion you
 > > have to feed your data as a multiplexed PS/PES into /dev/ost/video or
 > > as separate PES into /dev/ost/video and /dev/ost/audio.
 > 
 > How can I do this? My intention is to record a TS Stream to the harddisk
 > (maybe with cat /dev/ost/dvr > /... or something) and than play it and
 > see several parts in slow motion. I do not have a big machine, so I
 > guess, it is impossible for me to change in realtime a TS in PS/PES data
 > without dropping frames, or is it not so problematic as I think?
 > 

You don't need much speed for that. The PES packets are already in the
TS you just have to strip the TS headers and put the PES together. I
have done that in ntuxplayer. Just call "ntuxplayer -i TS_STREAM -n
-a APID -v VPID  <filename>" and it will playback the file using APID
and VPID as audio and video PID, respectively. The -n option tells the
player tu use /dev/ost/video instead of /dev/ost/dvr, that is why I
also have to use the -a and -v option, because I can't use the section
filters of /dev/ost/dvr in that case and I don't have my own filters
implemented in ntuxplayer, yet. Anyway, you can now use slow motion
and fast forward. It plays back well on a Celeron 300, so there
shouldn't be any problems.

Marcus

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Dr. Marcus Metzler                             
mocm@netcologne.de                     http://www.metzlerbros.de
mocm@convergence.de                    http://www.convergence.de

Convergence Integrated Media GmbH          
Rosenthaler Str. 51                   
D-10178 Berlin                             
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