[mythtv-users] Draft revisions to HowTo section 3.3, second try

Bruce Markey bjm at lvcm.com
Wed Apr 23 15:57:58 EDT 2003


Ray Olszewski wrote:
> Based on this morning's feedback -- both directly to my first draft and 
> on other issues that were discussed in the last day -- I've revised the 
> draft update a good bit. Here is the new version, for comments and 
> criticisms.

Here are a few suggestions and comments in the spirit of
improving the documentation. You've taken on some touchy
issues and handled them well. I especially like your
explanation of DMA.

...
> 3.3.1 CPU Type and Speed
> 
> Selection of CPU type and speed is the trickiest element of hardware 
> selection, mainly because there are so many tradeoffs one can make, 
> among number of things the MythTV device can do simultaneously, capture 
> size, and encoding quality.
> 
> MythTV has two modes of operation. It can function as a software video 
> encoder, which means that it uses a fairly generic "dumb" video capture 
> card to get frames of video, encodes them using the CPU on your 
> motherboard and writes them to disk. High-end video capture cards and 
> devices like the Tivo and RePlay have dedicated encoder chips which use 
                             ReplayTV

...
> 3.3.3 Hard Disk(s)
> 
> Encoded video takes up a lot of hard disk space. The exact amount 
> depends on the encoding scheme, the size of the raw images, and the 
> frames per second, but a typical value for MythTV is 2 GB/hour. Allow 
> enough space.

typical values for MythTV range from 700MB/hour to 2 GB/hour.

[the default mpeg4 parameters are less than a 800MB/hr.]

...
> 3.3.4 Video Capture Card
> 
> The system needs one of more video-capture cards for which Linux kernel 
> modules exist. We know of no complete list of video-capture cards known 
> to work with Linux; the "Cards" file that ships with kernel-bttv 
> documentation is one place to check. The most common, inexpensive cards 
> available are cards that use the bt848 or bt878 vidcap chip; examples 
> are the "Hauppauge WinTV Go" card and the "AverTV Desktop PVR" card. 
> They use the bttv kernel module.
> 
> After you have installed a suitable card in a pci slot, you can check 
> that the kernel sees it with "lspci". Look for an entry labeled 
> "Multimedia video controller". To get more detailed information about 
> the card, use "lspci -v" or "lspci -vv".

[this paragraph is installation/configuration and probably
belongs in a video troubleshooting section (which would need
to cover more than lspci ;-). The current docs seem to assume
that not only do you have a card installed, the driver is
loaded and you can probe and read video from /dev/video.]

...
> 3.3.5  Sound card
> 
> The system needs a sound card, or an onboard equivalent on the 
> motherboard, to play back sound and, in most cases, to record sound. Any 
> sound card that can be operated by the alsa (Advanced Linux Sound 
> Architecture) kernel modules will work with MythTV.

[Is this true? Might there be cards that have ALSA support
that do not handle full duplex properly?]

...
> 3.3.6 Video Display Card
> 
> If you want to view television on a computer monitor, then you can use 
> any video card for which there is an XFree86 driver that supports xVideo 
> (xv) extensions. Check the XFree86 documentation for details if you are 
> uncertain about your preferred card.
> 
> Most people, though, want to view television on a television set. For 
> this, you need either (a) one of the relatively small number of cards 
> with TV-out outputs that are supported by Linux and XFree86, or (b) an 
> external VGA-to-TV converter.
> 
> For choice (a), MythTV users on the mythtv-users mailing list report the 
> following experience:

[Replace the following paragraph]
> 
>     nVidia: recent nVidia cards (such as the GeForce4 MX440) are 
> reported to work with the nvtv drivers, available at 
> http//sourceforge.net/projects/nv-tv-out/;  and with the drivers 
> provided by nVidia itself at 
> http://www.nvidia.com/content/drivers/drivers.asp .
> 

       nVidia: all cards with tv-out that are supported by
   the current drivers from nVidia should be able to display
   on a television. Some cards with certain chip sets support
   overscan adjustment.

   See: http://www.nvidia.com/content/drivers/drivers.asp

   Many older nVidia cards (such as GeForce2 cards with tv-out)
   can use <A HREF=http//sourceforge.net/projects/nv-tv-out/>nvtv</a>,
   a utility which provides controls for overscan, x,y position
   and several other useful controls to fine tune output.

[GeForce4 MX440 is a card that specifically does not work
with nvtv ;-]

...
>     ATI: ATI is adament that it does not support use of its cards on 
> Linux systems, and official XFree86 offers no support either. Some 
> people report making some ATI cards work with the *experimental* version 

                                with the *experimental* "devel" branch

> of the GATOS drivers, available in CVS at 
> http//gatos.sourceforge.net/watching_tv.php.
...



More information about the mythtv-users mailing list