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 Post subject: live TV without delay
PostPosted: Sun Sep 21, 2008 6:41 pm 
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Joined: Sat Jan 26, 2008 10:28 pm
Posts: 53
Location: Montreal, Canada
Anybody know how to get a live feed from the pvr card without a delay? I am trying to play an old school SNES and it works through mythtv, but with a 5 second delay. Eventually I will get mythgame to do it for me.

mplayer /dev/video0

gets close but there is still a short delay, maybe it just isn't possible for the card to display fast enough

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roofchop
KnoppMyth R6, Antec Fusion, Asus P4P800-VM, Pentium 2.8Ghz, OCZ 2x1Gb RAM, 500Gb SATA, Hauppauge 2 PVR-150MCE, Nvidia GeForce 5600, Samsung SyncMaster 225BW (VGA), Optoma HD65 Projector (DVI)....


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PostPosted: Mon Sep 22, 2008 7:04 pm 
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Location: Melbourne, Australia
AFAIK, ALL digital TV boxes must have a buffer in order to function.
If this is so then you will find it impossible to remove the delay, since it is caused by buffering.

Mike

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 Post subject:
PostPosted: Mon Sep 22, 2008 8:08 pm 
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Joined: Sat Jan 26, 2008 10:28 pm
Posts: 53
Location: Montreal, Canada
Thanks Mike that is kind of what I figured. Makes sense to me.
roofchop

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KnoppMyth R6, Antec Fusion, Asus P4P800-VM, Pentium 2.8Ghz, OCZ 2x1Gb RAM, 500Gb SATA, Hauppauge 2 PVR-150MCE, Nvidia GeForce 5600, Samsung SyncMaster 225BW (VGA), Optoma HD65 Projector (DVI)....


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 Post subject:
PostPosted: Wed Sep 24, 2008 4:11 am 
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Joined: Wed Mar 03, 2004 7:43 pm
Posts: 748
Location: Sydney, Australia
If mplayer isn't fast enough, something like ttv, xdtv, tvtime or aatv might be a few milliseconds faster, as might a different TV/video capture card.

Decreasing buffers in V4L could also help, but I am really guessing now :-)

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 Post subject:
PostPosted: Wed Sep 24, 2008 8:07 am 
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Joined: Sat Sep 02, 2006 9:17 am
Posts: 359
It would be a suggestion for the Myth devs, and not particular to KM, but I don't see why they can't initially display directly from the card; then switch over as the disk buffer gets established.


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 Post subject:
PostPosted: Wed Sep 24, 2008 11:40 pm 
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Joined: Mon May 10, 2004 8:08 pm
Posts: 1891
Location: Adelaide, Australia
It has been suggested to the devs before (a long time ago, but probably multiple times), and they didnt like the idea of the added complexity.

See the first of the "Ideas with Response" on this page:
http://www.mythtv.org/wiki/index.php/Feature_Wishlist


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 Post subject:
PostPosted: Thu Sep 25, 2008 9:49 am 
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Joined: Sat Sep 02, 2006 9:17 am
Posts: 359
Wait, lemme check my Developer to English phrase book... (flip,flip,flip) Oh here it is...
Code:
I don't like the idea of the added complexity.

Quote:
1. "That sounds hard to do." and/or 2. "There's more interesting things I'd rather work on." and/or 3. "*&%@-off, I'm busy."


Oh well. Of course, if lots of people suggest something, there's an implied challenge that makes the work seem more appealing. I bet if TiVo, and Cable Co. DVR's lost their lag; The added complexity would simplify PDQ.

At one recent family gathering we had the same game on in two rooms; one room had about a 3-second delay. Hearing the other room cheer or jeer early was really ruining the game for those with the DVR and the better screen. Other than that, I've never been bothered by the lag. There's probably only a very few people for whom it's a real hassle, so it just makes sense to focus on things like multirec, that really do make the platform more appealing.


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 Post subject:
PostPosted: Fri Sep 26, 2008 10:25 am 
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Joined: Thu Mar 15, 2007 9:26 pm
Posts: 39
jmckeown2 wrote:
I don't see why they can't initially display directly from the card; then switch over as the disk buffer gets established.

I do. If your playing the media as soon as it starts, there is no way for the buffer to actually build, it's not like internet streaming where it comes in as fast as your net can and builds the buffer from that, with TV the stream is a constant speed, the same speed as the playback.


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 Post subject:
PostPosted: Fri Sep 26, 2008 11:09 am 
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Joined: Fri Apr 02, 2004 10:08 am
Posts: 1637
Location: Virginia, USA
The original poster was trying to play videogames through the video input card of the system.

Since that post the thread has become more about "directly displaying what the card is getting" versus "buffering the recording" and why MythTV can't just display what the card is getting.

Seems to me that without buffering, there's no point in using MythTV or any DVR. That's basically the whole idea behind DVR: being able to pause and rewind live TV. Just did a search and even TiVo says a 3-5 second delay is normal due to buffering.

If you just want to watch live TV, then use an application that lets you access the signal coming in to the card... someone mentioned tvtime (that's what I remembered from way back but it doesn't look like it's been updated since 2005). I know that HDHomeRun users can connect to the tuners via a URL and VLC, no buffering involved.


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 Post subject:
PostPosted: Sat Oct 11, 2008 3:52 am 
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Joined: Fri Sep 15, 2006 12:16 pm
Posts: 292
If your TV doesn't have an extra input you should buy a splitter to switch between the TV seeing the mythtv box and the game box.


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