[mythtv-users] Premium Content

Joe Votour joevph at yahoo.com
Tue Mar 27 22:45:35 UTC 2007

> Joe Votour wrote:
> I wonder if it would be possible for Myth to store dual versions of
> encrypted HD content, one encrypted full resolution, one downsampled to
> SD resolution.  It could determine commercial positions using the
> downsampled version, and apply the markers to the encrypted data for
> commercial skipping.  It could display the HD content at full res
> through a cable card enabled decryptor that doesn't expose the MPEG
> stream to the bus, unless the OSD needed to be displayed in which case
> it would cut the HD and show SD with the overlays (do you really need
> full HD when the overlay is showing?).
> Complicated, and uses much more storage, but it might be the only
> workable way to get commercial HD channels in a FOSS project.  A side
> benefit would be that you would automatically have SD versions for SD
> only frontends.
> Jeff.


This would not work (very well anyway).

The reason it would not work is because the MPEG-2 stream would be
different between the SD and HD versions (different bitrates and/or
different MPEG-2 encoders would mean different MPEG-2 streams).  Thus,
what is the beginning of an I-frame (for example) in the SD stream might
be the middle of a completely different frame (at a different time offset,
that is) of the HD stream.

Secondly, most MPEG-2 decoders should be good enough to handle getting
partial frames and wait for full ones, but this is CableCard after all,
and I like/trust CableLabs about as much as I can throw them.  (I worked
for a cable modem company once, and had to follow the DOCSIS
specification, as well as deal with the political BS that is CableLabs. 
It was not pretty.)

Finally, I would not be too happy with my 16:9 picture changing to 4:3
just so that the OSD can be overlaid on top of it.  Seems like a lot of
effort (and as I said earlier, you might get bad artifacting, or even a
completely different part of the show when doing it) for little return.

-- Joe

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