[mythtv-users] Re: HDTV, Myth, HD-2000, HD-3000, questions galore (and hopefully answers from the smart people... )

[Blammo [doh]]

Great list of questions. Hopefully we can get some answers to these,
and I"ll happily collate them into the master.

-blam



On Mon, 24 Jan 2005 15:04:24 -0600, Paul Leppert <phlepper at gmail.com> wrote:
> Blammo,
> 
> How about questions related to HDTV setup in mythtv?
> 
> - How are HDTV channels set up? Using zap2it and an HDTV lineup
> resulted in a mix of NTSC and ATSC channels with incorrect freqid for
> the digital channels (e.g., in Chicago, Channel 7 (ABC) is actually
> broadcasting on 52).  How is this set up via mythtv?
> 
> - How are HDTV subchannels set up?  Again, based on above, ABC is
> multicasting on 52.  In mythtv, are the channels specified as freqid
> 52-1, 52-2?  or some other format?  How should these multi-channels be
> set up for names (mythtv channel input won't allow '.' (7.1, 7.2,
> etc.) or '-' (7-1, 7-2).  Do these channels need to be renumbered
> (e.g., 900, 901)?  For me, I cannot seem to get any other subchannel
> other than the first regardless of what I put in the freqid field in
> mythweb (using an HD-3000).
> - Based on http://thegeorges.us/mythtv instructions, the mythconverg
> database needs to be tweaked to set channel format to ATSC (assuming a
> default of NTSC).  Is this necessary?  What are the correct commands
> for setting this up?
> - If your mythtv setup receives OTA NTSC and ATSC, is there any reason
> to keep the NTSC channels within mythtv?  If so, how should these be
> set up (similar issues as above since you now have two (or more)
> channel 7's)?  Is there a priority scheme within mythtv to make sure
> it records a show off the ATSC stream before choosing the same show on
> the NTSC stream?
> - Does transcoding need to be set up in mythtv for HD channels (my
> understanding of the HD stream is that it contains all subchannels.
> Does mythtv filter out the "extra" subchannels or do you need to use
> the transcoding mechanism to reduce the file sizes?)  I have no idea
> how any of this works in mythtv.
> 
> And questions for performance:
> 
> - What components of the mythtv / computer setup impact performance of
> HDTV (e.g., at a given hardware level, what is the CPU usage for
> recording?  what is it for playback, what is it for both)?
> - Related to above, what is the impact of multiple HDTV captures
> (e.g., two HD-3000 cards) on the processing requirements of the PC?
> Anybody here yet?  Anybody have an idea of what it takes
> processing-wise for HDTV PIP with two cards?
> - What can be done to improve performance (how is resolution reduced?
> Is there any impact (or even capability) of recording at lower
> resolution than 720p or 1080i/p? Is there an easy way to playback at
> different resolutions (via mythtv rather than different modelines).
> - If a modeline is set up for a particular monitor at a particular
> resolution, does that automatically reduce the processing of an HDTV
> stream (in other words, if I'm playing a 720p ATSC stream (1280x720)
> back on a monitor at 480p (704x480), have I somehow reduced the
> processing impact, or is the mythtv box still handling the full
> processing impact and all that is happening is a reduction in quality
> on the output)?
> - For playback, what is the processing impact for different
> resolutions (playing back a 720p stream at 1280 x 720, 1024 x 576, 800
> x 450)?
> - For those trying to get the best performance (at the tradeoff of
> quality), what is the best way to play back HDTV?  Reducing playback
> resolution?  Transcoding to reduced resolution? etc. etc.
> - What about audio?  Are there general rules about digital audio and
> performance or is this generally "not an issue" based on using a 5.1
> sound card (e.g., SB Audigy)?
> - What is XvMC and how does / will that help with the processing
> requirements of HDTV playback?  Are there particular video cards this
> will / will not work with?  Anyone have real world examples of
> processing improvements (e.g., CPU usage) with XvMC and without?
> 
> And a general question:
> 
> - Is there a way to tell within mythtv what format the ATSC is being
> broadcast (720p, 1081i, etc.)?
> 
> Wish I had more answers than questions, but as I get up the learning
> curve (and I receive my new, faster CPU), I should be able to
> contribute some real-world experience with my HD-3000 (and PVR-250 if
> I can ever get them working together).
> 
> Thanks,
> Paul
> --
> I hear and I forget. I see and I remember. I do and I understand.  --  Confucius
>