[mythtv-users] Export to MPG without re-compressing

[Joseph Fry]

On Fri, Oct 1, 2010 at 7:34 PM, Damian <myth at surr.co.uk> wrote:

>  Hello all,
>
> Can someone tell me if there's a way to export TV recordings to MPG (or any
> other standard format) without re-compressing? I have several recordings
> that I'd like to take off of my system and archive away. I don't want to
> re-compress them to do this though. I'd like to keep the quality as high as
> possible.
>
>
What you are looking for is "lossless" transcoding.  It is possible only if
you are not changing the video compression algorithm used.  IOW, if you want
to change container formats.  So the nuppelvideo (.nuv) files could be
transcoded to an MPEG2 MKV, MPV, AVI, etc. losslessly so long as the NUV
contains MPEG2 data.  Lossless transcoding is typically very fast.



> If I can also use cut points to get rid of commercials and footage before
> and after the programs begin, that would be great. But my guess is that I
> can't do that without re-compressing.
>
>
You can perform lossless transcoding with cutlists to remove unwanted
content but not recompress the video.


> Can I export the files to MPG?
>
>
.mpg is a container format (
http://en.wikipedia.org/wiki/Comparison_of_container_formats), much like
nuppelvideo, AVI, and many others.  If the actual video stream is in encoded
in a .mgp compatible video codec, then it is possible to do a lossless
transcode and just change the container format as described above.

Most capture cards produce one of only 2 or 3 formats these days.  In the
us, mpeg2 is the OTA broadcast format, while in the UK they use h.264 (MPEG4
AVC).  So I would wager that your video is already in a "standard format",
it is just in a not so commonly used container format.

Read up on transcoding with mythtv, paying particular attention to doing
lossless transcodes with cutlists.  There are several ways to do it,
including automatically as a post-recording job.
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