[mythtv] Anyone working on direct MPEG2 encoding?
ou401cru02 at sneakemail.com
Thu Jan 1 17:40:24 EST 2004
On Thu, 1 Jan 2004 22:24:53 +0100, "Kenneth Aafl°y" said:
> Chris Petersen wrote:
> > Chris Osgood wrote:
> > > I'd like to encode directly to MPEG2 off my bttv card so
> > > that I can use the PVR350's hardware decoder for output.
> > > Now that ffmpeg supports mpeg2 encoding are there any plans
> > > to add that as a direct encoding target?
> I'm pretty sure nobody is working on this, and I would really like to
> see this as a feature, as long as the fact that (for the most part) what
> you reffer to as mpeg2 encoding, would become libavcodec supported
> encoding. This would also have the side effect (if i'm not mistaken) of
> adding (with a little effort) support for this to mythtranscode.
First off, implementation won't be trivial but not too difficult. Making
an mpeg2 compliant stream isn't hard using libavformat. libavcodec can
do the encoding. However, I can't imagine this working in real time. I
think using mpeg2enc would be a bad idea. libav* is already well
integrated in mythtv, and the ffmpeg guys have been doing a lot of work
on mpeg2 lately.
Once it is there, it would allow rtjpeg/mpeg4->mpeg2 transcoding, but it
wouldn't be helpful for the mpeg2->mpeg2 commercial-cut stuff (which is
mostly working now anyway). It may help with getting frame-exact cuts
though (though I plan to do this in a different way using gop-exact cuts)
Anyhow, I'm not aware of anyone working on it, though last time I
proposed to attempt it (knowing a lot less about MPEG2 than I do today),
there wasn't all that much interest.
Note that the quality won't be great, since real-time encoding is 1-pass
(I believe the 1st pass is used to determine how to allocate the
bandwidth, whereas the second does the encoding...and that doesn't work
well in real-time). In general incorporating a two-pass encoder won't be
easy. Better to just use one of the currently availiable tools for the
job (nuvexport comes to mind)
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