[mythtv-users] Transcoding HD-PVR Recordings

Nick Rout nick.rout at gmail.com
Tue Sep 21 03:40:10 UTC 2010


On Tue, Sep 21, 2010 at 2:33 PM, Bob Sully <rcs at malibyte.net> wrote:

> > Date: Mon, 20 Sep 2010 15:39:33 -0400
> > From: Doug Vaughan <r.d.vaughan at rogers.com>
> > Subject: Re: [mythtv-users] Transcoding HD-PVR Recordings
> >
> > John and Kirk,
> >      I regularly edit and transcode HDPVR recordings. There are some
> > restrictions which may not suit you but here is what I do.
> >
> > 1) I locked my STB to 1280x720p output. This keeps the recording size
> > down but allows me to reliably use a video editor.
> > 2) I use a compiled version of Avidemux 2.4 as I found at least the
> > Ubuntu packaged version could not handle the audio AC3 tracks. Avidemux
> > has not worked for me with 1920x1080i HDPVR recordings. I have reliably
> > edited up to 8Gb files if the 1280x720p restriction is adheared to.
> > Although I rarely record more than 6Gb HDPVR file.
> > 3) I edit the HDPVR recording as needed then save as an avi with copy
> > audio and copy video settings.
> > 4) I run a ffmpeg copying the audio and video tracks to change the
> > container from avi to mkv. This also sets a seek table that reliably
> > works with the MythTV internal player.
> > 5) If you want to transcode the mkv file use HandBrake either the GUI or
> > the CLI. I have several presets for various sizes of transcoded video.
> > Handbrake already has iPod presets that you can use. I transcode the
> > output to mkv files. If you want to use the cli then you can cut and
> > paste their iPod presets from the GUI. That was my starting point when
> > building my customized presets.
> > 6) Occasionally the audio can be out of sync which I correct with a
> > feature of MKV File Creator GUI. MKV File Creator will not accept the
> > HDPVR recordings directly you need to at least change their container
> > type with a ffmpeg copy.
> >
> > As I can write python and bash scripts, outside of the manual editing or
> > audio resync, the whole process has been automated. I even initiate the
> > process as a right click script in Nautilus. The transcoding occurs as
> > an overnight cron job.
> >
> > This would not be what everyone would want but has worked well for my
> > needs almost two years now.
> >
> > Doug
>
> Doug:
>
> This is exactly what I do, with pretty good results.  I do a two-pass
> ffmpeg to transcode the HD-PVR file to an .avi, then use avidemux to cut
> out the commercials.  Two questions:
>
> (1) No matter how I tweak the HD-PVR settings (right now set to 11M bit
> rate), usually a 1-hr raw HD-PVR recording runs about 1.7GB in size (also
> at 720p from the STB).  The quality seems VERY good, however.  I would
> think that if the bitrate was low that the quality would be poor, but this
> isn't the case - but the file sizes imply that it it IS low.  How are you
> tweaking your HD-PVR settings?  Mine are set at boot time via the settings
> in the wiki.
>
> (2) Step 4:  Can you give us the syntax of your ffmpeg command to convert
> your .avi file from avidemux into a .mkv?  I have noticed occasionally
> that the audio will be out of sync on playback until I hit the back- or
> forward-arrow key, then it's fully in-sync for the remainder of the
> playback.
>

Step 4: I believe mkvmerge should be able to do this too.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mythtv.org/pipermail/mythtv-users/attachments/20100921/12c9e29e/attachment.htm>


More information about the mythtv-users mailing list