[mythtv-users] OT: A question on the HD-PVR and non-HD content

[Mark Buechler]

Hi

On Wed, Feb 18, 2009 at 3:56 PM, John P Poet <jppoet at gmail.com> wrote:

> On Wed, Feb 18, 2009 at 12:46 PM, Mark Buechler <mark.buechler at gmail.com>
> wrote:
> > Hi
> >
> > On Wed, Feb 18, 2009 at 2:01 PM, John P Poet <jppoet at gmail.com> wrote:
> >>
> >> On Wed, Feb 18, 2009 at 11:20 AM, Matt Emmott <memmott at gmail.com>
> wrote:
> >> > This is independent of the current state of Myth, VDPAU, H.264, trunk,
> >> > etc
> >> > etc, but I think this list would be the most knowledgeable on the
> >> > subject:
> >> >
> >> > I plan on getting an HD-PVR sooner than later. I plan on the
> >> > component-out
> >> > going from my STB to the HD-PVR, and the usb from the HD-PVR going to
> >> > the
> >> > Myth box. My question, or questions now that I think about it are: Is
> >> > this
> >> > box HD-only, or can I use it to tune SD content as well? Second, will
> it
> >> > automatically adjust between 720i/p and 1080i/p?
> >> >
> >> > The reason I ask is, I'd like the HD-PVR and STB connection to be my
> >> > primary
> >> > tuner, and function like my old Tivo + STB - It would "just work". I'm
> >> > hoping that the box could automatically adjust between SD / HD and
> HD's
> >> > different resolutions and record appropriately. I don't mind if SD
> comes
> >> > across in some kind of an H.264-esque wrapper, so long as it, again,
> >> > "just
> >> > works".
> >> >
> >> > Hope this isn't too far off topic but thus far I haven't been able to
> >> > get a
> >> > straight answer. Thanks in advance.
> >>
> >> The wiki talks about this stuff, but here is a summary:
> >>
> >> The HD-PVR understands 480i, 480p, 720p and 1080i.  It always encodes
> >> to H.264, and it will do it at whatever resolution the input is.
> >>
> >> For recording, Myth checks what resolution the HD-PVR is reporting and
> >> will tell the HD-PVR to use a user-defined bitrate based on that
> >> resolution.  So, 480i can be configured to use a much lower bitrate
> >> than 1080i, since the extra bits will not help the picture quality.
> >>
> >> LiveTV is the exception.  It takes the HD-PVR a couple of seconds to
> >> sync to a new input resoution.  Myth doesn't want to wait that long,
> >> and ends up giving up on the HD-PVR.  So, for LiveTV, Myth will ignore
> >> the input resolution and always select the maximum user-defined
> >> bitrate.  It still takes several seconds to change channels, but it is
> >> "quick enough" that Myth will not give up on the process.
> >>
> >> http://www.mythtv.org/wiki/HDPVR
> >>
> >>
> >> John
> >> --
> >
> > John, concerning bitrate, can MythTV's frontend support bitrate changes
> on
> > the fly? Would it make sense to just start recording at the highest then
> > once the resolution is known, change the bitrate to the appropriate?
>
> No.  Unfortunately, any change to the bitrate causes the HD-PVR to
> stop streaming.
>
>
Hmm, I thought I had changed bitrates on the fly before though and the
HD-PVR/driver handled it fine.. I'm probably mistaken.

- Mark.
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