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

[John P Poet]

On Wed, Feb 18, 2009 at 2:23 PM, Mark Buechler <mark.buechler at gmail.com> wrote:
> 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.

If you tried it in Myth, and had the polltimeout patch applied, then
that is probably why it "worked".  The polltimeout patch recovers from
the HD-PVR hanging up.

If it was not in Myth, then please tell me the order of commands you
issued.  The HD-PVR is sensitive to the order in which it is told to
do things.  Maybe I have not found the right sequence to make that
work.  Or, maybe it is a timing issue.  It is possible that issuing
two commands too close together will cause the second command to be
ignored.

John
-- 
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