[mythtv-users] PVR Hardware

Paul Fielding paul at fielding.ca
Fri May 6 08:59:15 UTC 2005


----- Original Message ----- 
From: "Joe Votour" <joevph at yahoo.com>
> Pretty much every other PVR works the same way - you
> have to have some sort of buffer, if you want it to be
> smooth.  I could see a situation where the instant
> somebody presses the pause button, that it starts
> recording, but then you have two issues:
> 1. You can only go back to where you paused
> 2. There might be some display disturbance.

I agree, this would probably not be an ideal situation, probably not 
reasonable to implement.

>
> If MythTV were to keep recording constantly, then it
> would definitely have to be something that could be
> turned off.  Here's some bad things about recording
> all the time:
> 1. You're always using the tuner.  Therefore (as you
> pointed out), you can't record something else, if you
> only have one tuner (luckily, I have three).

I think it would need to be a prioritized thing - consider the tuner 
'available' even though it's still recording the loop.  If something else 
needs the tuner, then kill the loop and use the tuner for an active 
situation.   If the tuner is needed for something else then you're not going 
to be able to go back and watch TV while it's being used by something 
anyways, so losing the buffer in this situation wouldn't be a big deal. 
Then, once the tuner goes idle again, return to doing the loop.

> 2. Even more importantly, you're using the CPU.  I see
> this as an even bigger problem - no low power modes,
> because the CPU is in use, the hard drive (s) are
> recording data constantly, and also the PVR-x50 cards
> aren't exactly known for being cool.  For those people
> who are using software capture cards (or don't have
> very fast CPUs), this extra load could interfere with
> playback of DVDs or recorded shows.

This is true, CPU load could be an issue.  For this reason I would suggest 
it's a selectable feature that can be turned on or off.  If you're using a 
software encoder on a slow box, you probably don't want a constant buffer 
running.  But if I'm using hardware encoding and/or a really fast box, I'd 
rather use a bit of CPU and get my buffer back.   I'm not sure about a good 
way to deal with potential heat issues, though.  Perhaps a 'Your milage may 
vary sorta thing...?'.

>
> Also, even if you're recording all of the time, the
> ringbuffer will eventually run out of space, so you'll
> have to wrap to the beginning.

True, but being able to go back as far as the ring buffer lets you is better 
than being able to go back zero minutes because the buffer was killed.

>SNIP<
> I like the second idea (though I wouldn't dare try to
> implement it, it makes MythTV much more complicated, I
> think), and I'm deadset against the first one.  But
> hey, different strokes for different folks.

Yuppers.  :)  Again why I would suggest the feature can be turned on or off.

regards,

Paul




>
> -- Joe
>
> --- Paul Fielding <paul at fielding.ca> wrote:
>> ----- Original Message ----- 
>> From: "Joe Votour" <joevph at yahoo.com>
>> > MythTV itself imposes a three (or so) second delay
>> > from live TV.  This is not necessarily caused by
>> the
>> > capture card itself, more than to have video in
>> the
>> > ringbuffer when you activate the PVR functions
>> (i.e.
>> > rewind, pause, etc.).
>>
>> Actually, for me the delay is a big issue, because
>> while I'm happy to use
>> the guide, two other people in the house don't like
>> the guide and prefer to
>> surf.  This means that the PVR is extremely annoying
>> to them and they prefer
>> to go back to regular TV.
>>
>> What I'd like to see in MythTV is an option to keep
>> the TV recording
>> happening *all*the*time*.  Make it selectable if you
>> like, so that people
>> can turn it off if it doesn't meet their needs, but
>> two things could happen:
>>
>> 1. Keep the recording loop happening all the time,
>> even when you go back to
>> surf menus.  Hey, it works when you've started
>> officially 'recording' a
>> channel, so why not in the buffer loop?  As long as
>> Myth is turned on, the
>> loop is running.  This would allow you to not only
>> instantly return to the
>> channel you were watching, but you also haven't lost
>> the ability to rewind
>> back to see the stuff that went on while you were
>> surfing menus.   If
>> something else is currently using the tuner, then
>> fine, let it take the
>> tuner and you lose out, but if it's available, then
>> it should be looping.
>>
>> 2. Don't restart the loop when you change channels.
>>  This means 2 things,
>> as well: first, it means that the channels could be
>> flipped *quickly* -
>> channel surfing would be viable again.   Secondly,
>> why shouldn't we be able
>> to rewind back to see what we already watched on the
>> previous channel?  what
>> the heck, if I hit rewind and it rewinds past the
>> channel flip, that's OK
>> with me - maybe I want to go back and see something
>> again that I already
>> saw.   I certainly don't see a disadvantage to it
>> being there.  And the
>> ability to quickly channel flip would make points
>> for the people who want
>> it.
>>
>> Just my thoughts.  The way I see it, how hard could
>> it be to implement these
>> two things? (Not being a programmer, myself, of
>> course.... *grin*)
>>
>> later,
>>
>> Paul
>>
>>
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