[mythtv-users] How much space should transcoding HDTV to mpeg4 save?

devsk funtoos at yahoo.com
Mon Jan 22 22:31:04 UTC 2007


> Is there a way to load mplayer video filters to perform ivtc?

I only did the minimal stuff to make it work with some good encoding options and the parameters that nuvexport already uses. The options I selected are for high quality after experimenting with 4-5 movies and various combinations of options. I think ivtc video filters support can be added but that would need to go to generic mencoder.pm, rather than just x264 module. It will also require configuration option to make it a visible option to the end user of nuvexport. More changes than I can make. But we can file a ticket for xris to provide this support.

please append your request to the ticket at : http://svn.mythtv.org/trac/ticket/2976

-devsk


----- Original Message ----
From: Steven Adeff <adeffs.mythtv at gmail.com>
To: Discussion about mythtv <mythtv-users at mythtv.org>
Sent: Monday, January 22, 2007 1:53:50 PM
Subject: Re: [mythtv-users] How much space should transcoding HDTV to mpeg4 save?

On 1/22/07, Billy Macdonald <billymacdonald at gmail.com> wrote:
> On 1/21/07, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
> > On 1/19/07, ryan patterson <ryan.goat at gmail.com> wrote:
> > > On 1/19/07, Phill Edwards <philledwards at gmail.com> wrote:
> > > > > So I'm
> > > > > not too interested in down sampling the resolution of my recordings.
> > > >
> > > > Then you're not really going to downsize the size of the files very much,
> > > > then.
> > >
> > > Transcoding to a more efficient codec should allow smaller file sizes at the
> > > same quality.  MPEG-4 is capable of achieving equal quality with a lower
> > > bitrate compared to mpeg-2.
> >
> > Regular mpeg4(aka xvid)  for HDTV size doesn't have this advantage,
> > which is where h264 comes in, but you would have to do the encode
> > manually with mencoder (x264).
> >
>
> Also, a 1080i stream that you deinterlace to 1920x1080 will need more
> bandwidth now that it is a progressive format in order to look good,
> at least that is what I've discovered in my limited amount of
> transcoding so far.
>
> I'm still tweaking my HD transcoding settings.  Any plans to
> incorporate the improved HD encoding codecs in mythtranscode?

If you run an IVTC filter on the 1080i to get to 1080p you should
actually save space since you'll be dropping frames (30fps->24fps)

On 1/22/07, devsk <funtoos at yahoo.com> wrote:
> > but you would have to do the encode manually with mencoder (x264).
>
> I went ahead and wrote a module for mencoder x264 for nuvexport. Its pretty
> easy to extend nuvexport (hats off to its author for making it so easy to
> extend it).
>
> Put the attached X264.pm file in
> /usr/share/nuvexport/export/mencoder/.
> Apply this simple patch to /usr/bin/nuvexport by hand (just add the two
> lines marked with '+' in the right place):
>
> # diff -u /usr/bin/nuvexport.orig /usr/bin/nuvexport
> --- /usr/bin/nuvexport.orig     2007-01-19 18:10:06.000000000 -0800
> +++ /usr/bin/nuvexport  2007-01-21 21:06:41.000000000 -0800
> @@ -73,6 +73,7 @@
>              or die "You need mencoder in order to use nuvexport in
> --mencoder mode\n";
>      # ffmpeg - seems to work better and is the default
>          require export::mencoder::XviD;
> +        require export::mencoder::X264;
>      }
>
>  # Load the other export modules
> @@ -103,6 +104,7 @@
>      }
>      elsif ($export_prog eq 'mencoder') {
>          push @Exporters, export::mencoder::XviD->new;
> +        push @Exporters, export::mencoder::X264->new;
>      }
>      push @Exporters, export::NUV_SQL->new;
>
> Add this to your .nuxexportrc:
>
> <mencoder::X264>
>     multipass = yes
>     vbr       = yes
>     a_bitrate = 128   # Audio bitrate of 128 kbps
>     v_bitrate = 1800   # Remember, quantisation overrides video bitrate
>     width     = 640   # Height adjusts automatically to width, according to
> aspect ratio
>     height    = auto
> </mencoder::X264>
>
> adjust to taste. And off you go with the best looking video compression
> ever.
>
> -devsk

cool, the mplayer documentation has a lot of good info on the x264
options. Is there a way to load mplayer video filters to perform ivtc?

-- 
Steve
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