Difference between revisions of "Video capture card"

From MythTV Official Wiki
Jump to: navigation, search
(USB Capture Cards)
m (Reverted edits by Yadavs (talk) to last revision by Stevegoodey)
(281 intermediate revisions by more than 100 users not shown)
Line 1: Line 1:
'''Video capture cards''' are used to get the picture from the cable, aerial, or satellite television source into the PC (compared to [[video display card]]s which provide output). It decodes and captures the video signal from the channel you want to record.
+
'''Video capture cards''' are used to get the picture from the cable, aerial, or satellite television source into the PC.  
  
== Types of cards ==
+
They decode and capture the video signal from the channel you want to view or record.  Often video capture cards will include a tuner to capture an specific TV signal, and are therefore known as  'tuner cards'. (Video capture devices without tuners ''do'' exist; usually used in conjunction with an external tuner, such as HD-DVR capture devices recording content from cable or satellite STB which tunes the channel). Sometimes people mistake video capture cards with [[video display card]]s which provide the output to the (tv)screen.
===Analog framebuffer cards===
 
These cards are usually based on a [[chipset]] like the [[bttv|Bt848/878]] or Conexant cx2388x, and decode broadcast [[NTSC]], [[PAL]], or [[Secam]] television.
 
  
===Analog Hardware-MPEG cards===
+
{{HelpUs}}
These cards, currently the [[Hauppauge PVR-250]] and [[Hauppauge PVR-350]] and the [[AVerMedia M179]], have a video processor onboard which compresses the tuned video signal into an [[MPEG-2]] [[program stream]] before sending it into the computer.  The tends to greatly reduce the load on the entire machine (with certain technical [[caveats]]), and these cards are recommended for.. well for all systems, really, but specifically, for systems with more than one, and especially more than 2 tuner cards.
 
  
===Digital Hardware-MPEG cards===
+
== [[Analog Framebuffer Cards]] ==
Like the Analog Hardware-MPEG cards above, these cards have a video processor onboard which compresses the tuned video signal into an [[MPEG-2]] [[program stream]] before sending it into the computer. One example of such a card is the [[AVerMedia DVB-T 771]].
+
These cards (also called frame grabbers and software encoders) are usually based on a [[chipset]] like the [[bttv|Bt848/878]] or Conexant cx2388x, and decode broadcast [[NTSC]], [[PAL]], or [[Secam]] television. These cards deliver an unencrypted data stream to MythTV, which then encodes to [[MPEG-4]] or [[RTjpeg]] using software encoders. Advantages of this type of card are:
  
== Capture Card Matrix ==
+
* Low cost
Here is a matrix, listing cards with their related drivers.
+
* High flexibility -- you can choose your encoding method and employ filters prior to encoding
 +
* If you have the CPU power, MPEG-4 produces better quality with smaller file sizes than the [[MPEG-2]] used with most hardware encoding cards
  
{| border="1"
+
The main disadvantage of this type of card is the high CPU requirements. Depending on your encoding settings, you may need close to 1GHz of CPU speed to handle a single encoding stream, and more if you have multiple cards or want to play back while recording. MPEG-4 is particularly demanding; for systems with weaker CPUs, RTjpeg consumes less CPU time at the cost of larger file sizes and more digital video artifacts.
|-
 
! Card !! Driver !! Works with MythTV? !! Hardware-based encoding? !! CC Stream? !! CC MPEG2? !! Notes !! Reporter
 
|-
 
||Aimslab Video Highway Xtreme||[[bttv]]||Y||N||?||?||Non-standard internal audio-out pinout, but labeled on PCB. Requires BTTV Module parameters card=14 tuner=2||HeK
 
|-
 
||[[ATI All-in Wonder]]||na||'''N'''||na||na||na||Does '''not''' work with MythTV|| Unknown
 
|-
 
|[[ATI HDTV Wonder]] || kernel >= 2.6.15, cx88-dvb|| Y || N || ? || ? || broadcast HDTV || Unknown
 
|-
 
|[[ATI TV-Wonder]] || [[bttv]] ||Y||N||Y||?||''Discontinued'' || Unknown
 
|-
 
||[[ATI TV-Wonder VE]] ||[[bttv]]||Y||N||Y||?||''Discontinued'' || Unknown
 
|-
 
|[[AVerMedia M179]] || [[IVTV]] stable||Y||Y||?||?|| || Unknown
 
|-
 
|[[AVerMedia DVB-T 771]] || [[bttv]] I believe||Y||Y||?||?|| || WhyTey
 
|-
 
||[[ComPro VideoMate TV PVR/FM]]||v4l2 ||No||No||?||?||MythTV 0.19, Works with KdeTV|| Ola A
 
|-
 
||[[Compro VideoMate TV Gold Plus]]||saa7134||Yes||?||?||?||Audio capture from PCI bus works, see wiki writeup for more info||[[User:Lynchmv|Lynchmv]] 13:45, 2 June 2006 (UTC)
 
|-
 
||[[DVICO Fusion DTVDVB-T]]||? ||Y||?||?||?||DVB-T, [http://www.itee.uq.edu.au/~chrisp/DVICO-Linux/ more info]|| Unknown
 
|-
 
||[[DVICO FusionHDTV5 Gold]]||Kernel >= 2.6.17 ||Y||Y||?||?||Tested with 2.6.17. Read more at link||Jason
 
|-
 
||[[DVICO FusionHDTV5 RT Gold]]||Kernel >= 2.6.15 ||Y||Y||?||?||DVB Driver from linux kernel 2.6.16, Works out of the box on Ubuntu 6.06 [http://www.fusionhdtv.co.kr/eng/Products/RTGold.aspx more info]. The analog tunner is visible by the kernel on the V4L driver - not yet tested in Mythtv|| Jylups
 
|-
 
||FireWire capture||na||Y||na||??||??||Caption stream is avail when playing through cable box, but not through mythtv|| Unknown
 
|-
 
||[[Hauppauge DEC2000-T]]||? ||Partial||?||?||?||DVB-T, '''USB''' external tuner|| Unknown
 
|-
 
||[[Hauppauge Nexus S]]||? ||Y||?||?||?||DVB-S, STV02998 based Mpeg Encoder|| Unknown
 
|-
 
| [[Hauppauge PVR-500]] || [[IVTV]] >= 0.4.0 || yes || yes || no || no || Dual TV tuners, single FM Radio tuner. || Unknown
 
|-
 
| [[Hauppauge PVR-350]] || [[IVTV]] stable || Y || Y || Not supported in MythTV || Y || Has TV-out and if the option to encode CC in MPEG datastream is enabled, PVR-350 TV output can also pass it back to the television CC decoder. Not recommended for new purchases, as mpeg decoding does not support advanced myth functions (like fast-forwarding) and future versions of myth will use OpenGL, which will not work on this card|| Unknown
 
|-
 
| [[Hauppauge PVR-250]] || [[IVTV]] stable || Y || Y || Not supported in MythTV || Y ||  || Unknown
 
|-
 
|[[Hauppauge PVR-150]] || [[IVTV]] stable||Y||Y||N||N|| || Unknown
 
|-
 
|[[Hauppauge WinTV-Go]] || [[bttv]] ||Y||N||Y||N|| || Unknown
 
|-
 
|[[Hauppauge WinTV 38061 Rev B226]] || [[bttv]] ||Y||N||?||?||Use btaudio for sound || Unknown
 
|-
 
||[[Hauppauge WinTV Nova-T PCI|Hauppauge Nova-T]]||[[bttv]] ||Y<=0.18.1 N==0.19||N||?||?||DVB-T, Digital Terrestrial|| Unknown
 
|-
 
||[[Hauppauge WinTV Nova-T PCI|Hauppauge Nova-T]]||[[cx88-dvb]] ||Y||N
 
!colspan="2"|Does CC in UK
 
|DVB-T, Digital Terrestrial|| [[User:Fishter]]
 
|-
 
||[[Hauppauge WinTV Nova-S PCI|Hauppauge Nova-S]]||CX88-DVB Kernel >=2.6.15 ||Y||N||?||?||DVB-S, Digital Satellite|| Unknown
 
|-
 
||[[Hauppage WinTV PVR (Roslyn)]]||na||'''N'''||na||na||na||Does '''not''' work with MythTV|| Unknown
 
|-
 
||[[Hauppauge WinTV-PVR-USB2]]||na||'''N'''||na||na||na||Does '''not''' work with MythTV|| Unknown
 
|-
 
||[[K-World Xpert DTV - DVBT PCI]]||? ||Y|| || || ||DVB-T, has aerial passthru|| Unknown
 
|-
 
||[[Matrox Rainbow Runner G-Series]]||mgavideo||Y||Y,mjpeg||N||N||''Discontinued''|| Unknown
 
|-
 
| [[pcHDTV HD-3000]] || kernel >= 2.6.12, cx8800, cx88-dvb, cx22702, or51132 || yes || no || no || no || broadcast HDTV. || [[User:rtsai1111]]
 
|-
 
| [[Plextor ConvertX]] || [http://oss.wischip.com/ wis-go7007-linux-0.9.7] || Y || Y || N || N || USB external device (MPEG4) || MythTV 0.18
 
|-
 
| [[Technisat AirStar HD-5000]] || kernel >= 2.6.x, dvb B2C2, LGDT330x  || yes || no || no || no || OTA and Clear QAM HDTV. || [[User:digitalboy]]
 
|-
 
||[[Terratec Cinergy 400]]||? ||Y ||N ||? ||? || || Unknown
 
|-
 
||[[Terratec Cinergy 600]] ||? ||Y ||N ||? ||? || || Unknown
 
|-
 
||[[Twinhan MiniTer DVT PCI]] || kernel >= 2.6.8 ||N ||N ||? ||? || DVB-T Australia. Provides MPEG2 stream from digital signal || [[User:Bill]]
 
|}
 
  
Removed from matrix because I could not find any info at vendor websites (please re-add if you have info about these!):
+
== [[Analog Hardware Encoder Cards]] ==
 +
These cards, currently the [[Hauppauge]] PVR cards, the AVerMedia M179 and any other card which supports the V4L2 MPEG Encoder API, have a video processor on-board which compresses the tuned video signal into an RTjpeg, MPEG-2, or MPEG-4 [[MPEG Stream|program stream]] before sending it into the computer. The advantages of these cards are:
  
* ATI TV-Wonder Pro
+
* Greatly reduced load on the entire machine (with certain technical [[#caveats|caveats]]). This is particularly important for machines with weak CPUs or when using multiple tuners in one system.
* Aver Desktop PVR
+
* The reduced load means that your video stream is less likely to suffer from encoding "hiccups" if a process causes the system to become momentarily too busy to process the video.
 +
* Most hardware-encoding cards output an MPEG-2 stream, which can simplify backing up to DVD.
  
== Detailed Information ==
+
The main drawback of this type of card is that you're limited to the video format and encoding options supported by the manufacturer (usually MPEG-2). You can transcode to MPEG-4 after recording to save space, if desired, but this requires post-record processing and will degrade quality slightly.
=== Cards that work ===
 
==== [[ATSC]] (HDTV) cards ====
 
* [[pcHDTV HD-2000]] (V4L w/pcHDTV patch -or- dvb driver) (Terrestrial only) (replaced by HD-3000)
 
* [[pcHDTV HD-3000]] (V4L w/pcHDTV patch -or- dvb driver) (Terrestrial and clear QAM)
 
* [[Air2PC]] (dvb drivers) (Terrestrial and clear QAM) (replaced by [[AirStar 5000]])
 
* [[AirStar 5000]] (dvb drivers) (Terrestrial and clear QAM)
 
* [[ATI HDTV Wonder]] (dvb drivers) (Terrestrial, clear QAM?)
 
* FusionHDTV 5 Gold or Lite (dvb & v4l cvs, mm kernels) (Terrestrial and clear QAM)
 
* FusionHDTV 5 RT Gold (dvb & v4l. kernels >=2.6.15) (Terrestrial and clear QAM)
 
  
==== Hardware Encoder cards ====
+
Most cards of this type are designed to encode standard definition analog (NTSC, PAL, or SECAM) video signals. At least one product, though, the [[Hauppauge HD PVR]], encodes analog HD output, as produced by cable or satellite TV boxes. Such a product is currently the only way to record HD content from providers that encrypt their digital data streams. (Some cable boxes have [[FireWire]] outputs, but cable operators often encrypt the IEEE-1394 output for some of the channels tuned by these boxes.)
* iTVC15 family of MPEG encoders supported by the [[IVTV]] drivers
 
** [[Hauppauge PVR-500]]
 
** [[Hauppauge PVR-350]] (TV-Out function works, but is not recommended, see details on this page)
 
** [[Hauppauge PVR-250]]
 
** [[Hauppauge PVR-150]]
 
** [[AVerMedia M179]]
 
* Matrox Marvel G200/G400 MJPEG encoders
 
  
==== Software Encoder cards ====
+
== Digital Capture Cards ==
* BrookTree ([[bttv]]) based cards. NOTE: The bttv page includes kernel parameters and links to vendor specs.
+
There are currently several HDMI capture cards and devices available on the market, but these will not work for capturing video. Nearly any device you may wish to record HDMI from will also be using HDCP to encrypt the stream, and as such cannot be used.
** BT848
 
*** [[Hauppauge WinTV-Go]]
 
*** Aimslab Video Highway Xtreme (VHX)
 
*** [[ATI TV-Wonder]]
 
*** [[ATI TV-Wonder VE]]
 
*** [[Hauppauge WinTV]]
 
*** [[Leadtek WinFast]]
 
*** [[Leadtek WinView 601]]
 
*** [[Pinnacle PCTV Studio]]
 
*** [[Pinnacle PCTV Studio Pro]]
 
*** Lifeview [[Fly Video]] II (Bt848) LR26 / MAXI TV Video PCI2 LR26
 
*** Lifeview [[Fly Video]] 98 LR50 / Chronos Video Shuttle II
 
*** Lifeview [[Fly Video]] 98/ Lucky Star Image World ConferenceTV LR50
 
*** Lifeview [[Fly Video]] 98/ MAXI TV Video PCI2 LR50
 
*** Lifeview [[Fly Video]] 98FM LR50 / Typhoon TView TV/FM Tuner
 
*** Lifeview [[Fly Video]] 2000 /[[Fly Video]] A2/ Lifetec LT 9415 TV [LR90]
 
*** Prolink PV-BT878P+4E / Lenco MXTV-9578 CP
 
*** Prolink [[Pixel View]] PlayTV pro / [[Pixel View]] PlayTV PAK
 
*** [[AVerMedia TVCapture 98]]
 
*** STB TV PCI FM, Gateway P/N 6000704 (bt878)
 
*** 3Dfx VoodooTV 100, Gateway P/N 6000699 (btt878)
 
*** Sigma TVII-FM
 
*** Zoltrix Genie TV/FM / TV-Max (people reported having Audio Issues with card)
 
*** Sabrent TVTuner (bt878)
 
** BT878 (Takes an MPEG2 HDTV(?) stream)
 
*** [[ATSC]] - pcHDTV / HD-2000
 
* Philips SAA7134-based cards
 
** Terratec Cinergy 400
 
** Terratec Cinergy 600
 
** [[Compro VideoMate TV Gold Plus]]
 
  
==== [[DVB]] cards ====
+
== [[Digital Tuner Cards]] ==
* Avermedia DVB-T (Bt8xx)
+
Digital broadcasting for [[DVB]], [[CableCARD]]/[[QAM]], and [[ATSC]] is in the form of an [[MPEG-2]] [[MPEG Stream|transport stream]], so unlike analog capture cards, there is no need for any kind of on-board encoding engine. The required [[MPEG Stream|program stream]] is extracted and handed directly to the computer for viewing or saving. Some cards have a hardware Program ID filter (hardware pid) which means the card can extract the required program stream from the transport stream itself. In either case, the computer power required to save a MPEG-2 transport stream (but not view it) is very small, being only what is required to shift data from the PCI/USB bus and save it to disk.
* DVICO FusionHDTV DVB-T ([http://www.itee.uq.edu.au/~chrisp/DVICO-Linux/ More Info])
 
* DNTV Live! DVB-T Pro ([http://www.itee.uq.edu.au/~chrisp/Linux-DVB/DNTV/ More Info])
 
* Hauppauge WinTV-Nova-T PCI Cards
 
* Hauppauge [[Hauppauge_WinTV_Nova-T_PCI|Nova-T]] (Digital Terrestrial)
 
* Hauppauge Nova-S (Digital Satellite)
 
* Hauppauge Nova-SE2 (Digital Sattelite)
 
* Hauppauge Nexus-S (STV02998 based) Mpeg Encoder
 
* Leadtek LR6650 DVB-T and other cards based on the Conexant 'reference' DVB-T design.
 
* Nebula Electronics DigiTV PCI Rev 1 (Bt878, Nxt6000) Rev 2 (Bt878, Zarlink MT352) (Digital Terrestrial)
 
* Pinnacle PCTV DVB-S (Bt878)
 
* Technisat [[Sky Star]] 2 PCI
 
* [[Twinhan MiniTer DVT PCI]]
 
  
==== USB Capture Cards ====
+
Confusingly, many useful tools for working with MPEG-2 transport streams have "dvb" in their names, even though they work just as well with MPEG-2 transport streams derived from "ATSC" broadcasts.
* [[Hauppauge DEC2000-T]]
 
* [[Hauppauge WinTV-NOVA-T-USB-2]]
 
* [[Pinnacle PCTV USB2 (pal Europe version)]]
 
* [[Plextor_PX-TV402U]]
 
  
=== Cards that don't work ===
+
Some digital capture cards also support analog ([[NTSC]] or [[PAL]]) transmissions, usually via a frame grabber. If your digital capture card lacks such hardware and you want to record both digital and analog transmissions, you'll need to buy a separate analog capture card - either a frame grabber or a hardware-encoding card. If your card does support multiple different modes, it will often be a '''hybrid''' tuner, rather than a full dual tuner. If that is the case, you will have to set up both inputs in the same [[Input Group]] to tell MythTV that they cannot be used at the same time.
* ATI All-in-Wonder cards<br>
 
<blockquote> 
 
The [http://gatos.sourceforge.net ATI drivers] provide a kernel module for basic V4L support which allows for capturing video from the device as it is playing. They do not, however, provide the tuner functions necessary for MythTV to select channels. Instead, they implement their channel tuning using the Xv extensions of X-Windows. A solution might be to patch the MythTV source code to recognize the ATI hardware and use Xv frequency changing to change the channel rather than solely relying on the V4L tuning functions. Then it would depend on whether the V4L support for capture is adequate enough in the ATI drivers for MythTV to work. It also might be possible to use an externally called Xv channel changing utility to change the channels.
 
</blockquote>
 
<blockquote>
 
The ATI All-in-Wonder card cannot (it is said elsewhere on the internet) send video across the PCI bus. It can only show video on the VGA output on the card. It is on this basis that neither the card nor drivers are appropriate for use with mythtv.
 
</blockquote>
 
* Hauppauge WinTV-PVR-Roslyn (P/N: 28552 on the TV Tuner).
 
* Hauppauge WinTV-PVR-USB2 (MPEG2 encoder box with USB2.0)
 
** http://pvrusb2.dax.nu/ a bare but apparently functioning userspace driver, no V4L so no MythTV for now.
 
** http://justiceforall.free.fr/pvrusb2.html A V4L driver for this card, but I'm not sure if it'll work with mythtv ;).
 
** http://www.isely.net/pvrusb2.html a driver by Mike Isely, actively maintained unlike the others. Is reported to work with MythTV.
 
* Cards based on the Conexant cx23416 MPEG encoder chip not already supported under ivtv (e.g. PVR2000).. development work has been done but cannot be considered a good solution for mythtv (yet).
 
* PVR-350 all functions work, but TV-Out isn't well suited for Myth, since it isn't accelerated and the MPEG decoder isn't well supported any longer.
 
  
== External Links ==
+
Some cable and satellite TV boxes include [[FireWire]] ports. You can use these ports, along with a FireWire port on your MythTV box, to record both analog and digital channels from the cable box. Essentially, the FireWire card and cable box function like a digital hardware MPEG card, although configuration details and capabilities differ. Depending on your cable operator, the channels tunable via the cable box may be the same as those that are tunable via a standard digital tuner card, or you may be able to record some or all of the cable system's encrypted channels, as well.
* [http://digitalboy.mythtvtalk.com/files/LinuxTvTunerGuide.pdf A Comprehensive Guide of TV Cards that Work with Linux]
 
* [http://digitalboy.mythtvtalk.com/files/MythTvTunerGuide.pdf The Comprehensive Guide of TV Cards that Work with MythTV]
 
* [http://www.mythtv.org/docs/mythtv-HOWTO-3.html#video_capture_device MythTV.org FAQ/Video Capture Device]
 
  
[[Category: Hardware]]
+
With the world moving towards digital broadcast standards, this type of card is likely to become dominant in the next few years.
 +
 
 +
[[Category:Hardware]]

Revision as of 10:51, 30 April 2013

Video capture cards are used to get the picture from the cable, aerial, or satellite television source into the PC.

They decode and capture the video signal from the channel you want to view or record. Often video capture cards will include a tuner to capture an specific TV signal, and are therefore known as 'tuner cards'. (Video capture devices without tuners do exist; usually used in conjunction with an external tuner, such as HD-DVR capture devices recording content from cable or satellite STB which tunes the channel). Sometimes people mistake video capture cards with video display cards which provide the output to the (tv)screen.


MythTV logo square.png Join us making your favorite media center even better than it already is today.

Analog Framebuffer Cards

These cards (also called frame grabbers and software encoders) are usually based on a chipset like the Bt848/878 or Conexant cx2388x, and decode broadcast NTSC, PAL, or Secam television. These cards deliver an unencrypted data stream to MythTV, which then encodes to MPEG-4 or RTjpeg using software encoders. Advantages of this type of card are:

  • Low cost
  • High flexibility -- you can choose your encoding method and employ filters prior to encoding
  • If you have the CPU power, MPEG-4 produces better quality with smaller file sizes than the MPEG-2 used with most hardware encoding cards

The main disadvantage of this type of card is the high CPU requirements. Depending on your encoding settings, you may need close to 1GHz of CPU speed to handle a single encoding stream, and more if you have multiple cards or want to play back while recording. MPEG-4 is particularly demanding; for systems with weaker CPUs, RTjpeg consumes less CPU time at the cost of larger file sizes and more digital video artifacts.

Analog Hardware Encoder Cards

These cards, currently the Hauppauge PVR cards, the AVerMedia M179 and any other card which supports the V4L2 MPEG Encoder API, have a video processor on-board which compresses the tuned video signal into an RTjpeg, MPEG-2, or MPEG-4 program stream before sending it into the computer. The advantages of these cards are:

  • Greatly reduced load on the entire machine (with certain technical caveats). This is particularly important for machines with weak CPUs or when using multiple tuners in one system.
  • The reduced load means that your video stream is less likely to suffer from encoding "hiccups" if a process causes the system to become momentarily too busy to process the video.
  • Most hardware-encoding cards output an MPEG-2 stream, which can simplify backing up to DVD.

The main drawback of this type of card is that you're limited to the video format and encoding options supported by the manufacturer (usually MPEG-2). You can transcode to MPEG-4 after recording to save space, if desired, but this requires post-record processing and will degrade quality slightly.

Most cards of this type are designed to encode standard definition analog (NTSC, PAL, or SECAM) video signals. At least one product, though, the Hauppauge HD PVR, encodes analog HD output, as produced by cable or satellite TV boxes. Such a product is currently the only way to record HD content from providers that encrypt their digital data streams. (Some cable boxes have FireWire outputs, but cable operators often encrypt the IEEE-1394 output for some of the channels tuned by these boxes.)

Digital Capture Cards

There are currently several HDMI capture cards and devices available on the market, but these will not work for capturing video. Nearly any device you may wish to record HDMI from will also be using HDCP to encrypt the stream, and as such cannot be used.

Digital Tuner Cards

Digital broadcasting for DVB, CableCARD/QAM, and ATSC is in the form of an MPEG-2 transport stream, so unlike analog capture cards, there is no need for any kind of on-board encoding engine. The required program stream is extracted and handed directly to the computer for viewing or saving. Some cards have a hardware Program ID filter (hardware pid) which means the card can extract the required program stream from the transport stream itself. In either case, the computer power required to save a MPEG-2 transport stream (but not view it) is very small, being only what is required to shift data from the PCI/USB bus and save it to disk.

Confusingly, many useful tools for working with MPEG-2 transport streams have "dvb" in their names, even though they work just as well with MPEG-2 transport streams derived from "ATSC" broadcasts.

Some digital capture cards also support analog (NTSC or PAL) transmissions, usually via a frame grabber. If your digital capture card lacks such hardware and you want to record both digital and analog transmissions, you'll need to buy a separate analog capture card - either a frame grabber or a hardware-encoding card. If your card does support multiple different modes, it will often be a hybrid tuner, rather than a full dual tuner. If that is the case, you will have to set up both inputs in the same Input Group to tell MythTV that they cannot be used at the same time.

Some cable and satellite TV boxes include FireWire ports. You can use these ports, along with a FireWire port on your MythTV box, to record both analog and digital channels from the cable box. Essentially, the FireWire card and cable box function like a digital hardware MPEG card, although configuration details and capabilities differ. Depending on your cable operator, the channels tunable via the cable box may be the same as those that are tunable via a standard digital tuner card, or you may be able to record some or all of the cable system's encrypted channels, as well.

With the world moving towards digital broadcast standards, this type of card is likely to become dominant in the next few years.