[mythtv] [mythtv-users] HD/SD Transcoding setup

Brad Templeton brad+mydev at templetons.com
Sat May 27 17:24:39 UTC 2006

On Sat, May 27, 2006 at 12:23:54PM -0400, Jeremy Silber wrote:
> The fundamental problem with this approach is that the user has to
> manually specify which transcoding profile they want based on the
> source content type... which means you have to have separate recording
> profiles for the same show occurring on different channels, and you
> have to know which channels are in 720p, 1080i, etc.  I think a better
> solution would be either:
> 1. mythtranscode realizes what format a recording is in, and can use
> this information to choose which transcode profile to use (for
> example, you could have a "perfect", "high quality", and "low quality"
> transcode profile from each source format.
> 2. allow transcoding based on the channel that was recorded, not just
> the show that was recorded.  Assuming that individual channels are
> always in the same format, this accomplishes the same thing as #1.
> Failing this, it would be nice if there was some way inside MythTV to
> see the format for each recording (an little 1080i/720p/480i/whatever
> icon in the "All Recordings" and "Delete Recordings" screen, perhaps.)
> -Jeremy

Well sure.  In fact if you go back in the archives you'll see me
wanting this and a lot more.   But there's what we can do today easily
and what will take more coding.

It is hard to come up with a general solution though.  There are
several purposes for transcoding...

a) I mean to play this on a smaller res screen  (which can mean
    the home myth TV system, or a laptop)

b) I just want the space saving that mp2 -> mp4 gives me at a similar
   quality.    I'm not willing to reduce quality.

c) I want to save disk space -- with varying tastes about how much,
   and alas, not the same for all resolutions.    Ie. a person may want
   their SDTV recordings to fit in 800mb/hour, and their HD ones to fit
   in 1.5gb/hour.    An ideal system might well try to let the user
   set a value, and have the system figure how to get to it by a
   combination of resolution reduction and mpeg4 quality reduction.

d) I want to stream -- like a Slingbox.   In this case I want fast
   transcoding, I want it starting the moment the recording starts,
   and I want it capped at a number that fits in my outgoing bandwidth.

Hard to come up with a design to meet all those different goals
especially since you might want multiple ones.

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