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

[John P Poet]

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.


John
-- 
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