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[linux-dvb] dvbstream and transcode



Hello all,

I've been thinking about Dave Chapman's dvbstream for a while. Earlier
on this year I put a few little fixes in (things like the use of poll
system call). I didn't update the main software CVS because the fixes
were quick work-arounds and I didn't want to put the code out.

Bearing in mind that I haven't touched the code since May my guess is
that it must be pretty stable. It's probably time to commit my changes
to CVS and let the world laugh!

However, I've also been using transcode to work with the output of
dvbstream and have run into problems. I'm not the first one to have
discovered this as recent postings to the transcode-users mailing list
reveal.

Finally, I record TV using a mixture of at jobs and the -n parameter to
dvbstream. Yuck!

So, what I'm think of is a new, improved dvbstream. It would pretty much
be a re-write from scratch (let's call it 2.0) and would have a few new
features.

Tuning from tzap, to avoid all those tedious manual parameters. In other
words something like:

	dvbstream "BBC ONE"

Getting it to start at or in a specific time:

	dvbstream --at 20:55 "BBC ONE"
or	dvbstream --in 15m "BBC ONE"

Where you could say things like 1d2h3m4s for 1 day, 2 hours, 3 minutes
and 4 seconds from now.

Getting it to run for a specific time (improvement to -n):

	dvbstream --at 20:55 --for 40m "BBC ONE"

Getting it to output to a file:

	dvbstream --at 20:55 --for 40m -o "AbsFabs.ts" "BBC ONE"

Getting it to do TS to PS conversion (it does this now):

	dvbstream --at 20:55 --for 40m --ps -o "AbsFabs.mpeg" "BBC ONE"

This last brings me onto the transcode problem.

dvbstream provides us with a slice of program. This doesn't compare too
favourably with a nice, properly formatted MPEG-2 file.

So, what I was thinking was putting a ``MPEG cleaner'' into the PS
generation. In other words finding out what annoys transcode about
dvbstream output and fixing it.

Secondary to this is getting the new dvbstream to spot transmission
errors and dropped packets and omitting them. At the moment dropped data
seems to cause a TRUNCATED packet which causes an error. The reader then
has to recover and skip the next correct packet to re-sync (because the
next packet's header has already gone past). Better would be to omit the
entire packet then bit-stream synchronisation would not be lost.

Does this make sense to anyone? How many people use dvbstream rather
than a more high-level application like VDR?

Looking forward to people's responses,

Jim.
-- 
Jim Darby <jim@jimbocorp.uklinux.net>
The Jimbo Corporation

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