[linux-dvb] Keep bitrates below 10Mbps...

Manu Abraham abraham.manu at gmail.com
Sat Oct 29 08:37:12 CEST 2005


Josef Wolf wrote:

>Hello!
>
>[ I hope I am on-topic here. I have considered to post this to the
>  tuxbox-forum, but decided to post it here because it has more to
>  do with stream encodings than with the dbox2.]
>
>I'm trying to transport live streams over a 10BaseT[1] network.  With
>most channels, there is no problem.  But on some programs (most notably
>the german ARD) the bitrate is changing pretty much.  After a lot of
>investigations, i've got some assumptions:
>
>- Most of the bandwidth is consumed by the video-pid (pid 101).  This is
>  not really a surprise.  I mention this here only because I need a reason
>  to ignore the other PIDs :)
>
>- Most of the time the bitrate on the video-pid is quite low (about
>  2000..3500 TS packets per second, which gives something below 7MBps).
>  But sometimes (every 10..20 minutes) the bitrate raises dramatically[2]
>  for a couple of seconds (sometimes just one second, sometimes up to 20
>  seconds) and comes down again to the 2000..3500 range.  I really don't
>  understand what is going on here.  How come this dramatic raise without
>  increase in the motion or in picture-details?  Is this raise really
>  caused by the video stream?
>
>  
>
>- Next, I checked how much stuffing (via adaptation field) is inserted.
>  It seems to me that about 6..8% stuffing is inserted.
>
>My guess is that with recoding the TS into PS, it should be possible to
>avoid this stuffing.  In addition, the TS header (another 2%) can be
>avoided.  With a little luck, this might be sufficient to get the bitrate
>below 10MBps (check footnote [2]).
>
>Can anyone confirm or correct my assumptions or have any other idea what
>might be going wrong here?
>
>  
>

Since the TS is constituted of more than the Video ES, the bandwidth 
occupied might very well depend on other factors.
I remember Johannes once saying that the EIT rate on the German Das 
Erste is quite high.

>I would like to try this recoding (TS->PS).  Extracting PES from the TS
>is not really a probem.  But unfortunately, I could not find any
>description how PS streams are to be constructed.  Any pointers?
>  
>

You can probably, check out replex from the Metzler bros, 
http://www.metzlerbros.org/dvb




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