On Sunday, Jan 19, 2003, at 15:06 Europe/London, Andrew Stevens wrote:
This is not always going to work as DVB allows higher peak bitrates than DVD.
Fortunately digital TV in the UK complies to DVD's 720x572 PAL resolution standard and bit rates tend to average around 4mbit for the best quality channels. I saw 7mbit as a peak once but that's still ok for DVD. We don't have HDTV in the UK, much to the chagrin of some enthusiasts and the balance tends to lean towards more channels at the expense of picture quality (or having cleverer video codecs at the "stream head"). The only real compatibility issue between broadcast MPEG2 and DVD is that a broadcast transport stream allows the aspect ratio to change on any I-frame boundary, something DVD doesn't allow within an individual disk title. This is not an insurmountable problem though.
Chuckle... if only it were so simple Half the code-complexity in mplexThe trouble is that the PC software uses an ordinary clock timer to start and stop the recording, like a normal VHS VCR, so there is usually extra unwanted video at the start and end. The mplex tool lets you chop unwanted material off the end with the -l option but I can't find a way to have the multiplexed output start from <n> seconds into the streams being muxed. The fact that mplex can segment the input streams into multiple standalone muxed files (e.g. for splitting across CDs) demonstrates that the principle is possible.
relates managing run-in / run-out correctly for (S)VCD and and it gets a lot
of help from the *encoder* which helpfully places end-of-sequence markers to
indicate where a clean split can take place.
Anyway, what is possible is that you can cleanly split at *closed* GOPs (one
where the initial frames do not refer to the previous GOP. It would not be
hard to modify mplex to spot the nearest closed GOP to a specified start-time
and start multiplexing from there. I'll see what I can do over the next
couple of days.
Thanks very much indeed. In return I shall point you towards my own contribution to the free software community, an app which lets you backup to DV camcorders. There's already something similar for Linux on sourceforge but this is for MacOS X (my platform) in case that suits you at all. Check out: http://www.versiontracker.com/dyn/moreinfo/macosx/17840 if interested.
Aside: if you can send me the commands you're using for splitting your DVBThe PVR s/w runs on PCs only but it records to a format which seems to
files (VDR .vdr's?) I can check it all works myself.
be referred to as "PVA". A free PC tool called PVAStrumento lets you
demux this, and it stores the results on my Mac's hard drive. It also fixes
any errors which occurred while the transport stream was being received.
I then do "mplex -V -f 8 -o output.mpg input.mpv input.mpa" then use
dvdauthor tools ifogen and tocgen to create the VIDEO_TS. That's it.
If there's a Unix tool which can replace PVAStrumento that would be
even better since the PVR s/w could then record straight over the wire
to the Mac (which has a useful 80GB hard drive) and spare me the
"Uncle Bill" experience. :-) It would let me script the process too...
Andrew
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