TiVo Community
TiVo Community
TiVo Community
Go Back   TiVo Community > Main TiVo Forums > TiVo Premiere DVRs
TiVo Community
Reply
Forum Jump
 
Thread Tools
Old 02-03-2013, 06:31 AM   #1
redbeard25
Registered User
 
Join Date: Jan 2002
Posts: 50
Lightbulb Watch four tuners at once?

This probably shows a bit of ignorance on my part, but here goes...

In Live TV, could Tivo have a mode where you can see all four tuners on your screen at once, kind of like DirecTV does with their "Mix" channels?

They could label them A, B, C, D and you could use those buttons on the remote - press once to select for trick play and hear the sound, twice for fullscreen.

Is there an engineering reason why they couldn't?
__________________
Roamio (upg to 3TB)
Mini LTx2
Stream

Former:
Premiere Elite LT + 1TB exp
TivoHD (upg to 1TB) LT
Stock TivoHD M2M
S2ST LT
S2DT 200GB
S2ST 200GB
Philips S1 (original 14hr version)
redbeard25 is offline   Reply With Quote
Old 02-03-2013, 07:00 AM   #2
compnurd
Registered User
 
Join Date: Oct 2011
Posts: 951
Mix Channel on Direct TV is a channel for them... It is not using multiple tuners on the box
compnurd is offline   Reply With Quote
Old 02-03-2013, 01:00 PM   #3
aaronwt
HD Addict
 
aaronwt's Avatar
 
Join Date: Jan 2002
Location: Northern VA(Woodbridge)
Posts: 14,024
You would need a decoder for each stream you are watching. So you would need four to watch four tuners simultaneously. The TiVo only has one MPEG decoder.
__________________
Roamio Pro
TiVo Mini x4
Roamio Basic OTA
39TB unRAID1--53TB unRAID2--36TB unRAID3
XBL/PSN: WormholeXtreme
aaronwt is offline   Reply With Quote
Old 02-03-2013, 07:14 PM   #4
unitron
Registered User
 
unitron's Avatar
 
Join Date: Apr 2006
Location: semi-coastal NC
Posts: 13,545
Quote:
Originally Posted by aaronwt View Post
You would need a decoder for each stream you are watching. So you would need four to watch four tuners simultaneously. The TiVo only has one MPEG decoder.
If you're quartering the screen and putting up 4 smaller versions of each stream that's being tuned, one decoder would be enough if it was fast enough and you had the software to send it the first line of the first channel, then the first line of the second, then the first line of the third, then the first line of the fourth, then the second line of the first, etc.
__________________
(thisismysigfile)


"I am altering the deal. Pray I don't alter it any further."

Darth TiVo, 14 February, 2011
unitron is offline   Reply With Quote
Old 02-03-2013, 07:26 PM   #5
aaronwt
HD Addict
 
aaronwt's Avatar
 
Join Date: Jan 2002
Location: Northern VA(Woodbridge)
Posts: 14,024
Quote:
Originally Posted by unitron View Post
If you're quartering the screen and putting up 4 smaller versions of each stream that's being tuned, one decoder would be enough if it was fast enough and you had the software to send it the first line of the first channel, then the first line of the second, then the first line of the third, then the first line of the fourth, then the second line of the first, etc.
The TiVo isn't designed for that.
__________________
Roamio Pro
TiVo Mini x4
Roamio Basic OTA
39TB unRAID1--53TB unRAID2--36TB unRAID3
XBL/PSN: WormholeXtreme
aaronwt is offline   Reply With Quote
Old 02-03-2013, 07:41 PM   #6
unitron
Registered User
 
unitron's Avatar
 
Join Date: Apr 2006
Location: semi-coastal NC
Posts: 13,545
Quote:
Originally Posted by aaronwt View Post
The TiVo isn't designed for that.
But if the single MPEG decoder was fast enough, it could be.

Hence my use of the word "If" in my previous post.

Not that I expect them to bother to design one that way to provide a feature that only a handful of owners would ever bother with on a regular after the novelty wore off basis.
__________________
(thisismysigfile)


"I am altering the deal. Pray I don't alter it any further."

Darth TiVo, 14 February, 2011
unitron is offline   Reply With Quote
Old 02-05-2013, 11:19 AM   #7
Dan203
Super Moderator
 
Dan203's Avatar
 
Join Date: Apr 2000
Location: Nevada
Posts: 25,226
That wouldn't work. MPEG-2 uses temporal compression, meaning frames are built using information from the frames around them. Basically one frame is only encoded with the information that makes it different from the previous frame. Not only that but the encoded order of the frames is not the same as the display order. Because of this the decoder has to maintain buffers of the reference frames. There is no way a single decoder could switch back and forth between 4 different streams without flushing those buffers and making it impossible to decode subsequent frames. The only way they could do this is if they decoded an entire GOP at a time. In MPEG-2 the average GOP is about 1/2 second so they would need a minimum 2 second delay to display 4 streams, plus the overhead of buffering to disk, display, etc... So probably about 5 seconds total. With H.264 however it becomes a LOT trickier. There aren't really GOPs in H.264. And there can be 10+ seconds between safe entry points in an H.264 stream. So if they tried the same trick they'd likely have to put a huge delay in and even then there is a high likelihood that there would be a lot of artifiacts and decoding errors in the video as you watched.

Dan
__________________
Dan Haddix
Super Moderator
Developer for VideoReDo
Dan203 is offline   Reply With Quote
Old 02-05-2013, 12:02 PM   #8
unitron
Registered User
 
unitron's Avatar
 
Join Date: Apr 2006
Location: semi-coastal NC
Posts: 13,545
Quote:
Originally Posted by Dan203 View Post
That wouldn't work. MPEG-2 uses temporal compression, meaning frames are built using information from the frames around them. Basically one frame is only encoded with the information that makes it different from the previous frame. Not only that but the encoded order of the frames is not the same as the display order. Because of this the decoder has to maintain buffers of the reference frames. There is no way a single decoder could switch back and forth between 4 different streams without flushing those buffers and making it impossible to decode subsequent frames. The only way they could do this is if they decoded an entire GOP at a time. In MPEG-2 the average GOP is about 1/2 second so they would need a minimum 2 second delay to display 4 streams, plus the overhead of buffering to disk, display, etc... So probably about 5 seconds total. With H.264 however it becomes a LOT trickier. There aren't really GOPs in H.264. And there can be 10+ seconds between safe entry points in an H.264 stream. So if they tried the same trick they'd likely have to put a huge delay in and even then there is a high likelihood that there would be a lot of artifiacts and decoding errors in the video as you watched.

Dan
See, I told you analog is better.
__________________
(thisismysigfile)


"I am altering the deal. Pray I don't alter it any further."

Darth TiVo, 14 February, 2011
unitron is offline   Reply With Quote
Old 02-06-2013, 12:44 AM   #9
Dan203
Super Moderator
 
Dan203's Avatar
 
Join Date: Apr 2000
Location: Nevada
Posts: 25,226
It's not a direct conversion but an uncompressed 4:2:0 1080i analog signal would require an equivelent of about 750Mbps of bandwidth. Use something like motion JPEG or I frame only MPEG-2 and you can cut that down to about 50Mbps. The average MPEG-2 stream broadcast by your cable company is about 14Mbps and H.264 streams are about 1/2 that. So you can understand why they use digital formats with temporal compression over analog. A slight loss of perceived quality and loss of a little flexibility in decoding can result in massive bandwidth savings.

And when we eventually transition to 4K that compression is going to be even more important. 4K requires about 3.4x as much bandwidth as 1080i when encoded with those same codecs. That's why the industry is pushing towards H.265, it's supose to cut bitrates by about 1/2 again compared to H.264 which will make up for a good chunk of that jump. Basically you'll be able to get 4K resolution in the same bandwidth currently used for MPEG-2 streams.
__________________
Dan Haddix
Super Moderator
Developer for VideoReDo
Dan203 is offline   Reply With Quote
Reply
Forum Jump




Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Advertisements

TiVo Community
Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
vBulletin Skins by: Relivo Media

(C) 2013 Magenium Solutions - All Rights Reserved. No information may be posted elsewhere without written permission.
TiVoŽ is a registered trademark of TiVo Inc. This site is not owned or operated by TiVo Inc.
All times are GMT -5. The time now is 10:43 AM.
OUR NETWORK: MyOpenRouter | TechLore | SansaCommunity | RoboCommunity | MediaSmart Home | Explore3DTV | Dijit Community | DVR Playground |