[linux-dvb] Keep bitrates below 10Mbps...
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 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
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 ).
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!
 Using 100BaseT is no option, since this is for the dbox2, which
is limited to 10BaseT by hardware.
 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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