[mythtv-users] Cutting commercials without expensive transcoding
Ray Olszewski
ray at comarre.com
Fri Mar 12 13:26:52 EST 2004
At 09:31 AM 3/12/2004 -0800, Chris Petersen wrote:
> > I use avidemux2. I allows me to cut commercials and
> > transcode from 3500/4400 vbr to 2200 for SVCD and it
> > only takes approx. 48 minutes for a 1/2 hour show
I've only skimmed this thread, but I think some responses in it are missing
the point of the original question. Let me use a separate example to try to
illustrate.
If I capture video directly as DivX (using vcr/avifile, or mplayer, or
whatever), I can use VirtualDub to edit out commercials. If I am willing to
accept the small imperfections that go with "keyframe editing", I can run
VirtualDub in "Direct Stream Copy" mode. So I can delete commercials by
hand, then process a file, all VERY quickly. Processing a 2-hour source
file takes me about 5 minutes (plus the editing time, which varies a lot
depending on how many commercial breaks are present, but is generally in
the 2-10 minute range).
Compared to this speed, "approx. 48 minutes for a 1/2 hour show" is a long
time, not an "only". That sort of time is, I'm sure, what the original
poster meant by "expensive". The speed advantage I get occurs because the
only processing needed is to keep the audio and video in sync (that is, get
things right at the container level), not to recode either the audio or the
video itself.
Keyframe editing is not perfect ... small snippets of commercials remain
after editing ... but I find it "good enough", given the speed benefit it
offers. I think the original poster is looking for some similar capability
in Myth ... the ability to clip out short bits ... most of the commercials,
for example ... without having to recode what remains.
The problem with providing this sort of quick-edit capability for Myth is
codecs. The internal encoding format used by Myth is non-standard, so an
outside application like VD can't handle it. The original poster has a
PVR250 and wanted to treat MPEG2 this way ... this should be doable in
principle, but in fact I don't know of any actual software (I've only
looked for Open Source/free software) that will do it ... I'm guessing due
to patent issues, but I really do not know why no one offers the ability to
keyframe edit MPEG2.
I did find a reference to a shareware (Windows) product called MPEG2VCR.
Its description say the following:
"No re-encoding when editing DVD-compliant MPEG2 captures from the latest
USB/DVD capture boxes. When using these sources to create a movie for DVD
burning, you will not have to wait for many hours while your movie is
re-encoded. Instead, your edited video will be written back to disk as fast
as any disk-to-disk copy operation."
See http://www.womble.com/products.htm for more details. But a $US 70, it
is not a cheap solution.
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