[mythtv] Lossless MPEG2 editing!

[Nigel Pearson]

>> only been tested on DVB recorded MPEG2 streams, but it works!
>
> I can't see how, as it's completely disregarding the internal file 
> structure.

	Yes, it does strip off .nuv headers, but the
resultant file plays normally in MythTV. Incredibly.
I haven't checked for errors on stdout/stderr yet.

	It is probably a raw MPEG2 file now?


>   Neither does it actually cut to the desired frame.

	Certainly not frame accurate - only cuts to the nearest
markup (DVB sequence header?). But the edits seem to be
accurate to at least the nearest half second, maybe less.
Definitely acceptable.



>> 2) Now, I assume that a recordedmarkup entry will always correspond
>>     to a sequence header or keyframe, but I am not sure if the
>>     audio and video blocks or packets will always align to these
>>     byte offsets.
>
> Not true at _all_.  Audio is commonly very roughly aligned with video 
> data -
> this is the reason for the 'extra audio buffering' option for playback.

	OK. So something that tries to trim ads out of a file
would need to recompress the audio? Or just adjust the length
of audio packets?


>>     Given that it doesn't actually transcode, I prefer having
>>     a separate program and set of UI actions for it. Thoughts?
>
> It shouldn't be part of anything,

	:-)

>  but if it has to be, it'd be best part of mythtranscode.
> Doesn't make sense to have vastly similar functionality part
> of a separate set of options and UI actions.

	Vastly similar? Both make a file smaller,
and mythtranscode _can_ use the cutlist I guess.

	If I wanted to burn some programmes onto a DVD,
I would want to not lose quality. If I wanted to keep
something on my backend for fast access, I would want
to compress it a little.

	For me, they seem to be different activities?


	Anyway, I will accept your sage wisdom and sit on
this for a while. But I think a lot of users are dying
for a lossless cutting utility. I know I was.

--
Nigel Pearson, nigel at ind.tansu.com.au | "Reality is that which,
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Office: 8255 4222    Fax:  8255 3153  |  in it, doesn't go away."
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