Introduction
On Thursday, 18 Jan 2007,
MerriLUG was proud to host
Jarod Wilson![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, who presented on MythTV. Sixty-one attendees made it to Martha's Exchange that night, making it the largest dinner ever, and one of the largest meetings, ranking up with Ted T'so and Linus. Jarod ran the meeting as a straight Q&A after a brief introduction, and finished with some striking demonstrations of the difference in quality between SD and HD captured video.
The MythTV home page is
http://www.mythtv.org![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
. There is an
official MythTV wiki![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, and a
source code/bug tracker![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
.
Jarod Wilson works for
Red Hat![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
in Tyngsboro. He is one of the authors of
Hacking MythTV![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
(Wiley). Sample chapter online:
MythTV Performance Hacks![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
.
Jarod's web site![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
includes a section on
Fedora Myth(TV)ology![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, which includes a detailed HOWTO guide.
What is MythTV?
MythTV is
Free Software which runs under the Linux operating system, and provides the functions commonly known as a
PVR/DVR (Personal/Digital Video Recorder)![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
. Essentially, it's a computerized, intelligent VCR, which uses hard disk instead of tape, and knows when shows are on so it can record them automatically. TiVo and ReplayTV are two commercial DVR products. Since it's open source software, if you don't like the way it does something, you can always change it — that's how much of its current functionality came about in the first place.
MythTV includes all the basic PVR functions, like recording and playing back scheduled programs, allowing you to schedule recordings automatically in advance, and pausing and rewinding live TV. MythTV also has a plugin system which permits it to be extended by other programmers. Plugins currently exist for playing external video, viewing photos, listening to music files, using your TV and a web camera as a video-telephone over the Internet, browsing the web, retrieving current local weather, and many other functions.
There is a
Gallery of MythTV setups![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
if you want to see what it can look like.
MythTV Operations
The MythTV system downloads it's Electronic Program Guide (EPG) data from
Zap2It.com![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, via an XML export feature. Zap2It requires free registration for this. Zap2It's motivation is apparently to avoid tons of screen scrapers hammering their web servers. Zap2It is operated by
Tribune![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
(incidentally, TiVo uses the same company for their EPG data). EPG is available 12 days ahead of air date.
If you have multiple MythTV boxes, you really should try and make sure they all have the same version. Compatibility between versions of MythTV is not good.
To show "live TV", MythTV records the live feed and then "immediately" plays it back again, in near-real-time. However, there is some lag introduced. Direct "pass-through" (without the record-and-play method) is not currently supported. This is being worked on.
Another feature being worked on is to separate music-playback into its own program. That will let one play music while browsing the web, viewing a photo gallery, etc. This is expected to be available Real Soon Now.
The MythTV wiki includes
information relating to the operating system![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
. This is of interest mainly because it has links to projects like
KnoppMyth![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
-- a "Live CD" which includes a canned installation of MythTV. Just put the CD in the computer and turn it on.
Broadcast technologies
Lingo
- Standard Definition (SD): The TV picture we've been watching for decades. 480i (480 interlaced lines). 640x480 resolution. Can be distributed via analog or digital means.
- High Definition (HD): The new TV picture. Various better displays, including 720p (720 progressive, non-interlaced lines) and 1080i. Surround sound capable. Digital only.
- Interlaced: TV draws odd lines, then even lines, alternating every frame.
- Progressive: TV draws all lines every frame. Yields a better picture.
- OTA: Over-the-air. TV signals broadcast from transmission towers. Think rabbit ears and roof-mount Yagi antennas
.
- Analog: The traditional over-the-air or cable TV systems we've been using for decades. Limited to Standard Definition.
- Digital: New over-the-air broadcast and cable systems are digital. All High Def TV is digital, but not all digital is High Def.
- NTSC: National Television Systems Committee
. The TV system we've used for decades. Analog.
- ATSC: Advanced Television Systems Committee
. The new digital TV standard.
Over The Air
OTA still exists and can work fine, even in this era of cable and satellite. If your house is conveniently placed to receive the signal, digital OTA can be of very high quality. Much of it (especially newer programming) is in high definition. And you can't beat the price.
OTA exists as two major types. Both are unencrypted and can be recorded by MythTV. Analog OTA (NTSC) is the classic analog TV system that's been around for decades. Analog TV is SD programming only. There are lots of tuners for NTSC. Digital TV (ATSC) is the new standard. It enables HD (High Definition) programming, but allows for SD as well. You need a digital tuner to receive ATSC, but they exist, too.
In southern NH, the big OTA stations are TV 2, 4, 5, 7, 9, 11, and 25.
Cable TV
First, a definition: "Basic cable" designates all the flat-rate channels you receive with a basic cable package, like History, Discovery, CNN, ESPN, TBS, etc. Basic cable does
not include "premimum" cable, like HBO, Cinemax, etc.
Cable TV also exists in analog and digital flavors. As with OTA, analog cable is limited to SD. In this area, analog basic cable is generally transmitted unscrambled, so you don't need a decoder box. That means it can work well with MythTV. Premium analog cable needs a cable decoder box. It is unknown to this author if such a decoder box can be hooked up to, and controlled by, a MythTV system.
Digital cable is a tricker beast. MythTV is not going to work for most digital cable programming. Most digital cable channels -- even basic cable -- are encrypted on the cable wire ("DRM"). Consumers are not permitted to decrypt it. You need a digital cable box to tune and decode the signal. That cable box will likely only output a digital High Def signal over an encrypted link to the TV. No consumer capture possible. HD component video from the cable box is not encrypted, but it is not feasible to capture a High Def signal from component video.
However, you may still be able to capture local TV stations via digital cable. Cable TV providers redistribute the high def, digital feeds from the local stations. The signals are generally re-modulated, as digital OTA broadcast uses
8-VSB![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, while digital cable prefers
256-QAM![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
. However, the local broadcast programming is often not encrypted -- so called "QAM in the clear". If that's the case, you can make use of it with MythTV. You generally don't even need to subscribe to "digital cable" -- the unencrypted feed comes down all the cable wires, regardless of subscribed services. If you already subscribe to basic analog cable, this can be an easy way to get a few HD channels, without messing around with antennas or paying extra for digital channels.
Per FCC rule, any modern (within the past few years) digital cable box must have a FireWire port, which can provide the digital video bitstream. Thus, if you have such a cable box and a FireWire port on your PC, you don't need a tuner/capture card. However, the bitstream will still be encrypted for most channels, so it doesn't solve that problem.
Compatibility matrix
Read from left to right. "Scrambled" indicates deliberate action is taken to make it hard for anything (MythTV included) to capture the content.
Delivery |
Signal |
Picture |
Programming |
Scrambled? |
MythTV |
Over-the-air |
Analog |
Std Def |
Local Stations |
Never |
Works great |
Digital |
Std Def |
Local Stations |
Never |
Works great |
High Def |
Local Stations |
Never |
Works great |
Cable |
Analog |
Std Def |
Local Stations |
Rarely |
Works great |
Basic Cable |
Rarely |
Works great |
Premium Cable |
Usually |
Possibly, if MythTV can control the cable box via "IR blaster" |
Digital |
Std Def |
Local Stations |
Sometimes |
Only if not scrambled |
Basic Cable |
Usually |
Unlikely |
Premium Cable |
Usually |
Unlikely |
High Def |
Local Stations |
Sometimes |
Only if not scrambled |
Basic Cable |
Usually |
Unlikely |
Premium Cable |
Usually |
Unlikely |
Satellite |
Any |
Std Def |
Any |
Either |
Possibly, if MythTV can control the satellite box via "IR blaster" or serial cable. Video capture is limited to analog Std Def. |
Hardware
Tuner/Capture Hardware
PVR Hardware database![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
has a list of configurations known to work, notes, etc.
Any card needs to be
Video4Linux (
V4L) compatible. There are dozens of compatible cards. Check the MythTV website for information on what works and what does not.
The pcHDTV
HD-5500![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
card is a good one. It supports both OTA and Cable, SD and HD,
in both analog and digital formats. While it may be a bit more expensive than other cards, pcHDTV specializes in Linux drivers and Linux support.
The Hauppauge
WinTV PVR![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
line is popular. Some notes on models:
- PVR-250 is a good start. The IR receiver (for remote control) is not the best.
- The hardware decoder on the PVR-350 is of limited use.
- The PVR-500 is a dual-tuner card, and functions just like having two PVR-250 cards.
One bit of hardware that Jarod recommended was the
HD Home Run![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
, from SiliconDust. It is basically an Ethernet-to-TV bridge. You plug coax into one side, Ethernet into the other, and you're in business. It contains everything you need to tune, capture, encode, and stream a TV signal over the 'net. It can be used with MythTV and other software as a capture device. This lets you put your TV input hardware in a different location than your MythTV backend storage hardware.
Remember that none of these devices will decrypt encrypted signals, so most digital cable channels will not be accessible without going through a cable box, and then only in Standard Def.
Other Hardware
Jarod recommended NVidia video display hardware, with the
binary-only, closed-source driver![](/pub/TWiki/TWikiDocGraphics/external-link.gif)
. He also recommended the use of the a config tweak in the X server configuration file: Set
UseEvents
to be
True
. He said the ATI cards can sometimes be made to work, but sometimes not, and all require too much effort.
Lots and lots of disk storage. The more, the better. Standard definition recordings consume about 2.5 gigabytes/hour. High definition recordings consume from 6 to 12 gigabytes/hour.
MythTV has an archiving plugin for archiving to DVD.
Any LIRC device (IR remote control) will work.
For playback, a 600 MHz PIII is minimum for std def. High def needs a lot more, perhaps a 2 to 3 GHz P4 or similar. There are a lot of things you can do in the area of performance tuning.
Network streaming (i.e., a recording stored on one box, playing on a different box, over the network) is possible. MythTV uses its own protocol, or you can use NFS/etc. Std def needs about 3 megabits/second. High def can use up to 17 megabits/second. Avoid wireless (802.11) -- even if nominal throughput is there, contention and packet loss will kill you.
Recommended vendors
Jarod Wilson's list of "good places to get hardware":
Other resources
About this document
Provided AS IS. Use information here strictly AT YOUR OWN RISK.
Contributions from: