[mythtv-users] Transcoding and deinterlacing, and other transcode issues

[Brad Templeton]

On Tue, Jun 13, 2006 at 07:47:27PM -0400, Robert Tsai wrote:
> On Tue, Jun 13, 2006 at 04:20:38PM -0700, Brad Templeton wrote:
> > c) I notice that once a recording is old, it vanishes from the
> > 'record' table where the 'transcoder' field would have been set for
> > it.  The 'recorded' table does not remember this, so if you
> > transcode an old recording you are going to get the system default.
> 
> The 'recorded' table also has a 'transcoder' field to let you
> transcode something after the fact (if for example auto-transcode is
> not enabled for a recording schedule). Maybe you are running some
> (very?) old version of MythTV?
> 
> But yes, I don't think there is any UI to manipulate this value once
> something has already been recorded.

That's right.   If you go to a recording, try to edit the recording
schedule, you will find, on the old recordings, that things like
the storage rules and transcode setting are grayed out.  You can
change the "do not record" to record the instance, and they will not
be grayed out, and you can set a transcording profile, however, as soon
as you save the settings the information is lost.

That's not a transcoder issue, but an issue with the lack of UI to
set this.

One can transcode with user jobs, or by hand, as I have done in
the past, but the point is to make it work more easily inside
mythtv, and to have a recording with indexes and the cutlist handled
properly etc.   (User jobs calling mythtranscode or nuvexport might
be able to do some of that.)

As for multiple profiles.   I tried editing the 'low' profile to
be a lossess one, and it didn't seem to work.  Creating my own lossless
profile and setting it on a recent recording was able to work.

As for the number of profiles an HD user needs, here are the ones I
think could be handy:


        a) Transocde 1080i to 720 lines, for people with 720 line TVs
        for whom storing the extra megapixel is of limited value.
            Goal: Reduce size, but lose no quality you would see on
            your TV.   De-interlace the 1080i of course before
            resizing.

        b) Transcode both 1080i and 720p to 1280x720 recordings at lower
            bitrates for long-term disk space saving.    Traditional
            transocding purpose, for which one may wish high, medium
            and low qualities.     For people with 1080 line TVs, they
            would possibly want different targets for 1080i than for
            720p.   1280x540 and 960x540 are common targets for
            "near HD" in a small filesize.

        c) Basic mpeg-4 encoding at about half the size of MP2 but
            similar quality.

        d) "Streaming" quality transcodes of SDTV that fit within
            your upstream bandwidth (384K or 512K for example.)

            Think of the slingbox, which is hardware which does this
            live.   Many PCs are also capapble of doing it live.

            The slingbox is used to watch video at your home in a
            remote location.   Handy when somewhere else to be able
            to pull up a video on your myth box and stream it.  Requires
            transcode, and stream.   But if pre-transcode is available,
            you can just scp it over and start watching it while it
            transfers with a short delay.

Other people commonly want profiles for offline storage.  This adds
to what people want, though I don't want it.