14 Mar
2007
14 Mar
'07
2:02 p.m.
Ethan Dicks wrote:
Cat just, um, cats.
In the same way that dogs dog? :)
What you may see from glommed MPEGs is a blip on the
screen or a chirp
from the audio as the decoder moves across the headers embedded in the
file, but even that's not guaranteed to happen - it all depends on the
particulars of the CODEC in use. MPEG, though, is reasonably tolerant
of cruft passing though - like when there's a scratch or a speck of
dust on a DVD, so it's unlikely to throw up its hands because it finds
a few dozen bytes that don't decode to sensible video.
That's certainly been my experience - just a short glitch between the file
originals where it seems to drop a frame or two, then it just carries on. I
didn't realise that it wasn't strictly part of the MPEG spec that you
*couldn't* just cat files together and expect it to work on all players
though, so my bad :)
With all of that said, I _think_ there's tools out
there that can
identify and remove those embedded headers.
I think the mencoder app which comes with mplayer does this; I seem to recall
reading somewhere that there's an option for recoding the data stream, which
presumbly removes all the headers and writes a "correct" file. Never tried it
on the few concatenated MPEGs that I have as I didn't think there was any
need, but now perhaps I should!