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

Josef Wolf jw at
Sat Oct 29 00:42:36 CEST 2005


[ 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?

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?

Thanks in advance!

[1] Using 100BaseT is no option, since this is for the dbox2, which
    is limited to 10BaseT by hardware.

[2] I have seen bitrates of up to 5400 TS-packets per second. This gives
    about 1015200 cps, which is obviously too much for a 10BaseT network

No software patents in Europe -- http://nosoftwarepatents.com
-- Josef Wolf -- jw at raven.inka.de --

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