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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.21">
<TITLE>Installing and using MythTV: Miscellaneous. </TITLE>
<LINK HREF="mythtv-HOWTO-24.html" REL=next>
<LINK HREF="mythtv-HOWTO-22.html" REL=previous>
<LINK HREF="mythtv-HOWTO.html#toc23" REL=contents>
</HEAD>
<BODY>
<A HREF="mythtv-HOWTO-24.html">Next</A>
<A HREF="mythtv-HOWTO-22.html">Previous</A>
<A HREF="mythtv-HOWTO.html#toc23">Contents</A>
<HR>
<H2><A NAME="s23">23.</A> <A HREF="mythtv-HOWTO.html#toc23">Miscellaneous. </A></H2>
<H2><A NAME="ss23.1">23.1</A> <A HREF="mythtv-HOWTO.html#toc23.1">I'd like to watch the files without using MythTV / I'd like to convert the files to some other format</A>
</H2>
<P>First, check if the <B>mytharchive</B> plugin does what you want. If not, then
read on:</P>
<P>MythTV comes with a utility called <B>mythtranscode</B> which can
decode nuv files into raw format for use with other applications. This
command-line utility was not designed to be used by the end-user, but
instead to be called by other applications or scripts. Programs like
<B>nuvexport</B> (
<A HREF="http://forevermore.net/myth/">http://forevermore.net/myth/</A>) are better suited for the end user.
However, since <B>mythtranscode</B> can be a useful tool, directions on
using it follow.</P>
<P><B>mythtranscode</B> creates raw streams, which means that they do not
contain any container information such as resolution, frame-rate, or audio
sampling rate. In order to process the output, you must supply this
information to the processing utility. <B>mythtranscode</B> provides the
relevant information on STDOUT.</P>
<P>There are two modes in which <B>mythtranscode</B> can create raw streams.
The first has no synchronization and assumes that the processing utility
will read audio and video at a constant rate. This method is useful when a
single application will be processing the raw output, such as
<B>mencoder</B> or <B>ffmpeg</B>. The second method assumes that two
separate applications will be processing the audio and video streams
independently, and there is no rate control between them which means that
the two programs don't coordinate their efforts to maintain synchronization.</P>
<H3>mythtranscode example</H3>
<P>First, start <B>mythtranscode</B>. You will need to determine the
channel and the start time manually.
<BLOCKQUOTE><CODE>
<PRE>
$ mythtranscode --chanid 1036 --starttime 2003-10-20T15:30:00 --profile \
autodetect --fifodir . &
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>When <B>mythtranscode</B> begins executing, it will create two FIFOs
("audout" and "vidout") in the directory specified (in this case ".",
meaning the current directory) and will print out information about the
video stream.</P>
<P>The next step is to start the processing application. The following assumes
that the stream is NTSC 640x480 with 32Kbps audio.</P>
<P>To use <B>mencoder</B> you would enter a command like:
<BLOCKQUOTE><CODE>
<PRE>
mencoder -audiofile audout -audio-demuxer 20 -rawaudio rate=32000 \
-rawvideo on:w=640:h=480:fps=29.97 -ovc lavc -oac mp3lame -o out.avi \
vidout
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>
<FIGURE>
<EPS FILE="stop.eps">
<IMG SRC="stop.png">
<CAPTION><B>NOTE</B>: You must use mencoder 1.0PRE1 or later. <B>mencoder</B>
version 0.9x <EM>WILL NOT WORK!</EM></CAPTION>
</FIGURE>
Using ffmepg:
<BLOCKQUOTE><CODE>
<PRE>
ffmpeg -f u16le -ar 32000 -ac 2 -i audout -f rawvideo -s 640x480 -r 29.97 \
-i vidout -vcodec mpeg4 -b 2000 -acodec mp3 -ab 128 out.avi
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Or to play directly using mplayer (again 1.0PRE1 or later is needed):
<BLOCKQUOTE><CODE>
<PRE>
mplayer -audiofile audout -audio-demuxer 20 -rawaudio rate=32000 \
-rawvideo on:w=640:h=480:fps=29.97 vidout
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>If you wanted to write the raw data to separate audio and video files for
later processing, the following would work (note the use of --fifosync
for rate-control):
<BLOCKQUOTE><CODE>
<PRE>
$ mythtranscode --chanid 1036 --starttime 2003-10-20T15:30:00 \
--profile autodetect --fifodir . --fifosync &
$ cat audout > audio.raw &
$ cat vidout > video.yuv
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H2><A NAME="ss23.2">23.2</A> <A HREF="mythtv-HOWTO.html#toc23.2">Using a different window manager</A>
</H2>
<P>MythTV is not dependent on any particular window manager. If you wish to
run a lightweight window manager, the <CODE>configfiles/</CODE> directory has an
example of a <CODE>.twmrc</CODE> and <CODE>.fvwmrc</CODE> file you may use.</P>
<H2><A NAME="capture_resolution_"></A> <A NAME="ss23.3">23.3</A> <A HREF="mythtv-HOWTO.html#toc23.3">What capture resolution should I use? How does video work?</A>
</H2>
<P>While MythTV allows you to set various GUI and capture resolutions, not
all combinations make sense.</P>
<P>First, analog video signals have a defined vertical resolution. In NTSC,
the video standard specifies that there are 525 vertical scan lines. Once
the "extra" lines are removed (they're used to synchronize the video signal,
and encode closed captioning data), you have 480 horizontal lines stacked
vertically.</P>
<P>In PAL, there are 625 "raw" lines of resolution, with a net of 576
horizontal lines stacked vertically.</P>
<P>Horizontally, the maximum value allowed for a Bt8X8 chip is 720. However,
due to limitations in the chip and other limitations of broadcast
television, there may not be a noticeable improvement in image quality
beyond 400 or 500 pixels.</P>
<P>With this in mind, there are certain commonly accepted values for
resolution. While other values may be accepted for the vertical
resolution, they will cause scan lines to be repeated or dropped.</P>
<P>From "best" to "worst", in NTSC:
<UL>
<LI>720x480 ("DVD" resolution. Also commonly, 704x480)</LI>
<LI>640x480 4:3</LI>
<LI>544x480 (TiVo high resolution)</LI>
<LI>480x480 (Video CD resolution)</LI>
<LI>352x480 (ReplayTV "Standard" quality)</LI>
<LI>320x480 </LI>
<LI>544x240</LI>
<LI>480x240 </LI>
<LI>352x240 </LI>
<LI>320x240</LI>
</UL>
</P>
<P>As you can see, the lower quality values are half of the better ones.
720x240 is possible, but isn't a good tradeoff relative to the number of
vertical lines lost. In a PAL country, the you would use values like
720x576 or x288.</P>
<P>The higher resolutions will be more CPU intensive if you're using software
encoding (PVR-250/350 will have minimal host CPU impact even if you're using
720x480). If the CPU is overtaxed, frames will be dropped causing uneven
motion. You will likely see the best results at resolutions which average at
least 10% CPU idle time. You can use system tools such as <CODE>top</CODE> or
<CODE>sar</CODE> to check the CPU % idle while recording. If the CPU average
usage is consistently exceeding 90%, frames will need to be dropped during
peak times when more than 100% of the available CPU would be needed to
process all of the frames.</P>
<P>If you'd like to read more on this, go to the vcdhelp website at
<A HREF="http://www.vcdhelp.com/forum/userguides/94382.php">http://www.vcdhelp.com/forum/userguides/94382.php</A>.</P>
<H2><A NAME="ss23.4">23.4</A> <A HREF="mythtv-HOWTO.html#toc23.4">MythTV GUI and X Display Sizes</A>
</H2>
<P>MythTV is designed to be run as dedicated full screen TV application
but can also be run as a desktop application on a computer monitor. Here
are a few consideration for configuring sizes to best suit you needs.</P>
<H3>X Dimensions</H3>
<P>For output to a Television, common resolutions are 640x480, 800x600, and
some rare devices support 1024x768. Generally, higher resolutions are
better. However, you may find that you prefer the picture quality at one of
the lower resolutions. Everything in MythTV is scalable and should 'fit'
regardless of the resolution you choose.</P>
<P>Edit your X configuration file, usually <CODE>/etc/X11/XF86Config-4</CODE> for
XFree, or <CODE>/etc/X11/xorg.conf</CODE> for Xorg, so that the resolution you
want to use is listed first in the lists under "Screen". If this resolution
is higher than the resolutions supported by your output device, you will see
a 'panning' effect where moving the mouse to the edge will scroll around a
desktop area which is larger than the display size. If this happens, edit
your X configuration file to match the display size then restart X.</P>
<H3>MythTV Dimensions</H3>
<P>From "mythfrontend" go to Setup->Appearance.
The default for the height and width is "0" - this will cause
MythTV to automatically size itself to full screen.</P>
<P>If the MythTV GUI width and height are not 0, mythfrontend uses these GUI
dimensions and is anchored to the upper left corner of the X Desktop. If
the GUI X and/or Y are not 0, the upper left corner is positioned at the
specified coordinates. If the "Run the frontend in a window" box is checked,
the window will have a frame and can then be dragged to any position on the
desktop.</P>
<P>
<FIGURE>
<EPS FILE="stop.eps">
<IMG SRC="stop.png">
<CAPTION><B>NOTE</B>: When the GUI is full screen, you may see windows rapidly
flipping on top of each other. If this happens you will need to set your
window manager to 'Click to Focus' for windows to stack properly.</CAPTION>
</FIGURE>
The fonts for the GUI and OSD will scale to whatever sizes you use. Most
font sizes can be changed in setup selections or in the .xml files under
<CODE>/usr/local/share/mythtv/</CODE> . Make sure to use fonts large enough
to be read on a TV screen from a distance.</P>
<P>The full screen TV size is based on the X display size. For Xinerama, you
can specify a screen in Setup->General. The TV picture will be stretched
to fit the entire GUI area regardless of the
<A HREF="#capture_resolution_">capture resolutions</A> used. However, during playback, the "W" key can
to used to correct differences between 16:9 and 4:3.</P>
<H3>Overscan Dimensions</H3>
<P>Because picture edges can be ragged and screen edges aren't straight,
Television is designed to project an image larger than the physical screen.
This is called "overscan". Underscan is fitting the entire image inside the
screen. Underscan is useful for computer monitors so that toolbars and
scrollbars at the edges can be seen.</P>
<P>For best results, match the X display area as close as possible to the edges
of the physical screen. This can only be adjusted by your tv-out device or
by the settings for the television set. Many sets have these adjustments in
a 'service mode'. If you cannot make these adjustments, there will be black
borders around the edges of the X desktop, MythTV GUI and TV playback.</P>
<P>MythTV has settings for "Overscan" in Setup->Playback. These can not, and do
not, cause the image to display beyond the edge of the X display area. The
purpose of these settings are to cut off rough edges and to expand the image
so that objects will appear to be the same size as a normal overscanned TV
picture.</P>
<H2><A NAME="backupdb"></A> <A NAME="ss23.5">23.5</A> <A HREF="mythtv-HOWTO.html#toc23.5">Saving or restoring the database </A>
</H2>
<P>See the <B>mysqldump</B> manpage for more information.
<BLOCKQUOTE><CODE>
<PRE>
$ mysqldump -u mythtv -pmythtv mythconverg -c > mythtv_backup.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>To restore: (assuming that you've dropped the database)
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u root
mysql>create database mythconverg;
mysql>exit
$ mysql -u mythtv -pmythtv mythconverg < mythtv_backup.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>You may need to alter the MySQL permissions if this database is being shared
with multiple systems. See the
<A HREF="mythtv-HOWTO-6.html#modify_perm_mysql">Modifying access to the MySQL database for multiple systems</A> section for more
information.</P>
<H2><A NAME="ss23.6">23.6</A> <A HREF="mythtv-HOWTO.html#toc23.6">Deleting the MySQL database</A>
</H2>
<P>
<FIGURE>
<EPS FILE="stop.eps">
<IMG SRC="stop.png">
<CAPTION><B>NOTE</B>: Performing this step will remove the entire database. You will lose all of your settings and will need to re-run the mc.sql script
to setup the database structure before running the mythtv-setup program.</CAPTION>
</FIGURE>
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u root
mysql> drop database mythconverg;
mysql> quit
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H2><A NAME="ss23.7">23.7</A> <A HREF="mythtv-HOWTO.html#toc23.7">Moving your data to new hardware</A>
</H2>
<P>This assumes that you will be moving your data to newer / bigger hardware
and don't want to lose your programs.</P>
<P>The first step is to create a database backup as demonstrated in an earlier
section.</P>
<P>Next, you will extract only the data that is relevant to the programs:
<BLOCKQUOTE><CODE>
<PRE>
$ grep "INSERT INTO record " mythtv_backup.sql > restore.sql
$ grep "INSERT INTO recorded " mythtv_backup.sql >> restore.sql
$ grep "INSERT INTO oldrecorded " mythtv_backup.sql >> restore.sql
$ grep "INSERT INTO recordedmarkup " mythtv_backup.sql >> restore.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P><B>NOTE</B>: Newer versions of <B>mysqldump</B> place backticks around
the table names. Backticks are not the same as apostrophes! On a typical
North American keyboard, backticks are located to the left of the "1" key,
on the same key as the tilde. Also, because the <B>bash</B> shell may try
to interpret the backticks, make sure you use a \ before each one.</P>
<P>If your <CODE>restore.sql</CODE> file is empty, you'll need to re-run the
commands like this:
<BLOCKQUOTE><CODE>
<PRE>
$ grep "INSERT INTO \`record\` " mythtv_backup.sql > restore.sql
$ grep "INSERT INTO \`recorded\` " mythtv_backup.sql >> restore.sql
$ grep "INSERT INTO \`oldrecorded\` " mythtv_backup.sql >> restore.sql
$ grep "INSERT INTO \`recordedmarkup\` " mythtv_backup.sql >> restore.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Note the space after the table name and the ">>" to append to the file for
all but the first <B>grep</B>. "recordedmarkup" is huge and may be
hundreds of thousands of lines if you had lots of hours of recordings.</P>
<P>After you have moved the data files to the new hardware, configure MythTV
using the <B>mythtv-setup</B> program as you normally would with a
standard MythTV installation.</P>
<P>At this point we will restore the information about your programs back into
the database:
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u mythtv -pmythtv mythconverg < restore.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>After successful insertion of the data you may delete the
<CODE>restore.sql</CODE> file.</P>
<H2><A NAME="btaudio"></A> <A NAME="ss23.8">23.8</A> <A HREF="mythtv-HOWTO.html#toc23.8">btaudio </A>
</H2>
<P>btaudio allows you to obtain the audio data from your tuner card directly
over the PCI bus without using a sound card. This is useful if you would
like to use multiple tuner cards in a system without adding a sound card for
each one, or if your existing sound card is not capable of full-duplex
operation.</P>
<P>In order to use btaudio, your tuner card will need certain hardware
installed on it, and that hardware must be wired correctly. The chip that
will allow you to use the btaudio module is the MSP34xx. However, having a
MSP34xx is no guarantee that you will be able to use the btaudio module.</P>
<P>As of 2003-03-31, this is the current list of cards and their status:
Works with btaudio:</P>
<P>
<UL>
<LI>Hauppauge WinTV-radio with dbx-TV stereo, model 401</LI>
<LI>Hauppauge WinTV-Theater, model 495, 498 (Europe)</LI>
<LI>ATI TV Wonder</LI>
</UL>
</P>
<P>The following cards do not work:
<UL>
<LI>Pinnacle Studio PCTV Pro - note: this has a MSP34xx, but it's not
wired correctly to the BT878 chip.</LI>
<LI>ATI TV Wonder VE</LI>
<LI>Leadtek Winfast 2000 XP (PAL, UK and NTSC)</LI>
<LI>I/O Magic PC-PVR. No MSP34xx chip.</LI>
</UL>
</P>
<P>The following cards have been reported to work, but have issues:
<UL>
<LI>Avermedia AVerTV Studio (no digital DSP output, "whiney noise" on
analog)</LI>
</UL>
</P>
<P>Once btaudio loads, it should register additional <CODE>/dev/dsp</CODE> and
<CODE>/dev/mixer</CODE> devices. Typing <CODE>$ dmesg</CODE> will let you know
what's going on.</P>
<H2><A NAME="ss23.9">23.9</A> <A HREF="mythtv-HOWTO.html#toc23.9">Removing unwanted channels</A>
</H2>
<P>If <B>mythfilldatabase</B> grabbed a channel which you do not want to
include in your TV listings, you can remove the entries from the grabber
configuration and the MySQL database. This often happens with premium
channels; for example, HBO or Showtime may be available on your cable TV
system, but is scrambled because you're not a subscriber to that channel.
Since you can never watch it, you want to get rid of it.</P>
<P>If you are using the DataDirect service, login to your account at
<A HREF="http://labs.zap2it.com/">http://labs.zap2it.com/</A> to
modify your lineup. Uncheck the boxes for any unwanted channels, and they
will no longer be included in your download.</P>
<P>If you are using a grabber from XMLTV, comment out the channel from the
<CODE>~/.mythtv/<sourcename>.xmltv</CODE> file by inserting the word "not
" (including the space) in front of the unwanted entry. This will prevent
<B>xmltv</B> from grabbing future listings.</P>
<P>Next, delete the unwanted item from the channel table so that it will not
appear in the EPG or when changing channels. To delete the data from the
database we need to perform some steps. First, assuming that HBO is channel
15, we need to find out the internal <CODE>chanid</CODE> used by MySQL:
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u root mythconverg
mysql> select chanid from channel where channum=15;
+--------+
| chanid |
+--------+
| 1015 |
+--------+
1 row in set (0.00 sec)
mysql> delete from channel where chanid = 1015;
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Old program data will be removed over the course of a week. However, you may
want to immediately delete any current program listings for the channel that
has been removed:
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u root mythconverg
mysql> delete from program where chanid = 1015;
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H2><A NAME="ss23.10">23.10</A> <A HREF="mythtv-HOWTO.html#toc23.10">NFS</A>
</H2>
<P>You may want to use a central server to store your files. </P>
<P>On the host machine, (in this case, the hostname is "masterbackend") you'll
want to edit your <CODE>/etc/exports</CODE> file and use something like:
<BLOCKQUOTE><CODE>
<PRE>
/var/video (rw)
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>To export the <CODE>/var/video</CODE> directory with read / write privileges.</P>
<P>On the "slave" machine, you'll want to edit the <CODE>/etc/fstab</CODE> file and
add something like:
<BLOCKQUOTE><CODE>
<PRE>
masterbackend:/var/video /var/video nfs rsize=8192,wsize=8192,hard,intr,nfsvers=3,actimeo=0
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Then run <CODE># mount -a</CODE> to re-read the file to mount the file system.</P>
<P>In this case, the source is a machine called "masterbackend" which is
exporting the directory "/var/video", which we're mounting locally at
"/var/video". The rsize and wsize options are used to increase the
performance of NFS; "hard,intr" is there because that's the recommendation
of the NFS-HOWTO, the nfsvers is required for filesizes over 2GB and actimeo
is used to turn off file attribute caching. Attribute caching for a shared
media point causes problems; you always want to see the latest state of the
directory and files. See
<A HREF="http://www.mythtv.org/wiki/index.php/Optimizing_Performance">http://www.mythtv.org/wiki/index.php/Optimizing_Performance</A> for
additional information regarding performance optimization.</P>
<H2><A NAME="ss23.11">23.11</A> <A HREF="mythtv-HOWTO.html#toc23.11">Automatically starting mythfrontend at system boot time</A>
</H2>
<P>Here's an example submitted to the mythtv-dev list by Pat Pflaum
<A HREF="mailto:pat@netburp.com">mailto:pat@netburp.com</A> using fvwm:
<BLOCKQUOTE><CODE>
<PRE>
$ cat > .xinitrc
fvwm &
mythfrontend
^D
$ cat > .fvwmrc
Style myth* NoTitle, NoHandles, Sticky, WindowListSkip, SloppyFocus, GrabFocus, BorderWidth 0
^D
$
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>The following also works with blackbox:
<BLOCKQUOTE><CODE>
<PRE>
$ cat > .xinitrc
xset -dpms s off &
irxevent &
mythfrontend &
blackbox
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Make sure that your <CODE>.blackboxrc</CODE> file has:
<BLOCKQUOTE><CODE>
<PRE>
session.screen0.focusNewWindows: True
session.screen0.focusModel: SloppyFocus
</PRE>
</CODE></BLOCKQUOTE>
in it.</P>
<P>
<A NAME="mythbackend_autostart"></A> </P>
<H2><A NAME="ss23.12">23.12</A> <A HREF="mythtv-HOWTO.html#toc23.12">Automatically starting mythbackend at system boot time</A>
</H2>
<H3>Red Hat And Mandriva</H3>
<P>Here's a method for automatically starting mythbackend submitted by Mike
Thomson (
<A HREF="mailto:linux@m-thomson.net">mailto:linux@m-thomson.net</A>) and Stu Tomlinson (
<A HREF="mailto:stu@nosnilmot.com">mailto:stu@nosnilmot.com</A>).</P>
<P>Copy the files from the MythTV <CODE>contrib</CODE> directory or from Mike's web
site (
<A HREF="http://m-thomson.net/mythtv/">http://m-thomson.net/mythtv/</A>) as follows:</P>
<P><CODE>etc.rc.d.init.mythbackend</CODE> should be made executable and copied to
<CODE>/etc/rc.d/init.d/</CODE>:
<BLOCKQUOTE><CODE>
<PRE>
$ cd contrib
$ su
# chmod a+x etc.rc.d.init.d.mythbackend
# cp etc.rc.d.init.d.mythbackend /etc/rc.d/init.d/mythbackend
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P><CODE>etc.sysconfig.mythbackend</CODE> should be copied to
<CODE>/etc/sysconfig/</CODE>:
<BLOCKQUOTE><CODE>
<PRE>
$ cd contrib
$ su
# cp etc.sysconfig.mythbackend /etc/sysconfig/mythbackend
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Edit <CODE>/etc/sysconfig/mythbackend</CODE> if you want to change the defaults
(the userid that should start mythbackend, location of the logfile and (if
required) the name and location of the mythbackend binary).</P>
<P>Use <B>chkconfig</B> to make sure the script is called when
entering runlevels 3, 4 or 5:
<BLOCKQUOTE><CODE>
<PRE>
$ su
# chkconfig --level 345 mythbackend on
# exit
$
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H3>Log files </H3>
<P>By default, the log file for mythbackend will be written to
<CODE>/var/tmp/mythbackend.log</CODE>. This has been tested and is known to work
on Mandriva and Red Hat, but many people prefer to place logs under
<CODE>/var/log/</CODE>.</P>
<P>To do this, create a group called <CODE>mythtv</CODE> (or anything you prefer)
and add your usual MythTV users to that group. If you changed the user that
starts mythbackend from the default of root you <EM>must</EM> perform this
step.</P>
<P>Create the directory <CODE>/var/log/mythtv</CODE> and set its
permissions as follows:
<BLOCKQUOTE><CODE>
<PRE>
$ su
# mkdir /var/log/mythtv
# chown root:mythtv /var/log/mythtv
# chmod 0775 /var/log/mythtv
# exit
$ ls -ld /var/log/mythtv
drwxrwxr-x 2 root mythtv 4096 Apr 28 21:58 /var/log/mythtv/
$
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H3>Mandriva </H3>
<P>Mandriva adds one more twist in the form of the <CODE>msec</CODE> utility,
which runs regularly and (at the default or any higher security level) sets
permissions on many files, including those under <CODE>/var/log</CODE>.</P>
<P>To tell msec about the MythTV log files and their directory, you need to
edit the <CODE>/etc/security/msec/perm.local</CODE> file to include the
following:
<BLOCKQUOTE><CODE>
<PRE>
# /etc/security/msec/perm.local
# Local overrides to the msec program
#
# Full file path user.group permissions
/var/log/mythtv/ root.mythtv 775
/var/log/mythtv/* root.mythtv 664
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>A copy of the above has been included in the contrib/ directory. You may
add it by typing:
<BLOCKQUOTE><CODE>
<PRE>
$ cd contrib
$ su
# cat etc.security.msec.perm.local >> /etc/security/msec/perm.local
# exit
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Finally run the <CODE>msec</CODE> tool to check and implement your
changes.
<BLOCKQUOTE><CODE>
<PRE>
$ su
# msec
# exit
$
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>
<FIGURE>
<EPS FILE="stop.eps">
<IMG SRC="stop.png">
<CAPTION><B>NOTE</B>: msec can only <EM>reduce</EM> the permissions of files, so if
you don't get the results you expect, check that you're not asking
<CODE>msec</CODE> to add missing permissions to the files or directories you
created.</CAPTION>
</FIGURE>
</P>
<H3>Gentoo</H3>
<P>The portage file for MythTV has scripts that will allow you to run
mythbackend at startup.</P>
<P>To run mythbackend as a daemon which starts at boot time:
<BLOCKQUOTE><CODE>
<PRE>
# rc-update add mythbackend default
</PRE>
</CODE></BLOCKQUOTE>
To stop mythbackend as a daemon:
<BLOCKQUOTE><CODE>
<PRE>
# /etc/init.d/mythbackend stop
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>To obtain a list of options:
<BLOCKQUOTE><CODE>
<PRE>
# /etc/init.d/mythbackend
</PRE>
</CODE></BLOCKQUOTE>
</P>
<H2><A NAME="advanced_backend_config"></A> <A NAME="ss23.13">23.13</A> <A HREF="mythtv-HOWTO.html#toc23.13">Advanced Backend Configurations </A>
</H2>
<P>MythTV is flexible in the way that you define multiple backend tuner
configurations. The only hard-and-fast rule is that the Master backend
<EM>must</EM> have a capture device defined, but shouldn't imply that the
capture device in the Master backend must be the first capture card defined in the
database.</P>
<P>One example of an advanced configuration is the round-robin scheme. Rather
than defining all of the cards on the master, you could first go into
mythtv-setup on the master to define globals such as the general configuration
and the channel lineup but not the host-specific configuration item like the
capture card. In this example, we will use a 4 tuner configuration, where two
slaves have one card each and the master has two.
<OL>
<LI>Add the first capture card on one of the slaves. Complete the
configuration, connecting the input source to the card. This will get
cardid #1 in the database. Exit mythtv-setup.</LI>
<LI>Configure the first capture card on the master backend. This will get
cardid #2 in the database. Exit mythtv-setup.</LI>
<LI>Configure the first capture card on the second slave. This will be
cardid #3 in the database. Exit mythtv-setup.</LI>
<LI>Configure the second capture card on the master backend. This will
get cardid #4 in the database. Exit mythtv-setup.</LI>
</OL>
</P>
<P>Using this scheme, the master backend will not use both capture cards until
one of the following happens:
<UL>
<LI>There are four recordings scheduled for the same time</LI>
<LI>Both slaves are unavailable</LI>
</UL>
</P>
<P>The scheduler in MythTV checks whether an encoder is available; if a slave
backend isn't running, its encoder isn't available, so the scheduler will
look for the next available encoder. This makes MythTV very flexible; slave
tuners can come and go, and as long as there are enough tuners for what
you'd like to record it doesn't matter which tuner in particular is going to
be used.</P>
<P>Using this round-robin scheme along with a shared storage directory like
NFS and enabling the Master Backend Override setting will allow you to view
content even if the slave backend that recorded a program is not available.</P>
<H2><A NAME="ss23.14">23.14</A> <A HREF="mythtv-HOWTO.html#toc23.14">Using the transcoder</A>
</H2>
<P>MythTV's built-in transcoder re-encodes recordings from one codec to
another. The transcoder has three primary uses; it can transcode MPEG-2
files captured using a hardware encoder (PVR cards, DVB cards, ATSC HD,
etc.) to MPEG-4, it can be used to transcode RTjpeg files (usually only used
on systems that can not real-time encode to MPEG-4 using a framegrabber) to
MPEG-4, and finally it can be used to remove commercials from a MPEG-2 file
while leaving the file in MPEG-2 format.</P>
<P>When MythTV transcodes a file to MPEG-4 or RTjpeg the resulting file format
is NuppelVideo (nuv). NuppelVideo is a container which provides a method of
keeping the audio and video in sync throughout the recording, which is why
it is used instead of the <CODE>.avi</CODE> format. You may have difficulty
playing <CODE>.nuv</CODE> files in non-MythTV systems.</P>
<P>The original file is removed when the transcoding process is complete.
Unless you're sure that you will be satisfied with the result you may want
to enable the <B>mythtv-setup</B> option which causes <B>mythbackend</B>
to keep the original file after transcoding. This option is on the second
page of the General section in mythtv-setup. Enabling this allows you to
compare the two files and restore the original if you like. Outside of the
initial setup phase it usually isn't necessary to leave this option enabled.
A recording can be transcoded in two ways:</P>
<P>
<UL>
<LI>Automatically transcode the file once it has completed
recording.</LI>
<LI>Manually choosing to transcode a recording, usually after
importing a cutlist or manually marking commercials to be
removed.</LI>
</UL>
</P>
<P>The second method can be used on files that have already been transcoded (or
files which were are already in the desired format), so only the frames
immediately following a cut section will be re-encoded, resulting in a
minimal loss of quality when removing commercials with the added benefit of
being extremely quick.</P>
<P>The current transcoding system has a lot flexibility, but there are
a number of steps involved in setting it up. In order to
automatically transcode a given recording you must do the following:
<OL>
<LI>Configure recording profile for your capture source and enable
transcoding on one or more profiles.</LI>
<LI>Configure one or more transcoding profiles.</LI>
<LI>Create or alter existing scheduled recordings to enable
transcoding for that recording.</LI>
</OL>
</P>
<H3>Configuring Recording Profiles to Allow Transcoding</H3>
<P>Enter the Utilities/Setup > Setup > TV Settings > Recording Profiles
section in <B>mythfrontend</B>. Choose the option that corresponds to
your capture source (ignore the Transcoders for now.) Choose the quality
profile you are interested in using for transcoding. Ensure that "Enable
auto-transcode after recording" is checked. </P>
<H3>Configure Transcoding Profiles</H3>
<P>Enter the Recording Profiles > Transcoders menu. There are three quality
settings to choose from and a two special Autodetect settings. Later, when
scheduling recordings you'll have to choose one of Autodetect, High, Medium,
and Low Quality transcode settings in addition to the recording profile we
set up above. If you choose the Autodetect transcoding profile for a
recording, MythTV will use the "Autodetect from RTjpeg/MPEG-4" profile for
recordings which are RTjpeg/MPEG-4 files. Otherwise, it will use the
"Autodetect from MPEG-2" profile provided it's an MPEG-2 recording. If you
choose one of the others (High, Medium, Low) it will use the settings in
that profile regardless of the codec of the original recording.</P>
<P>There are a number of options for transcoding but the simplest is to enable
lossless transcoding (the first option) which subsequently removes all other
options. Enabling lossless encoding simply removes commercials (if you've
marked them) and attempts to clean up MPEG-2 streams. Note that with this
option MythTV will not apply any sort of filters and will only attempt to
normalize the stream into something cleaner and less likely to have trouble
with other less forgiving MPEG-2 hardware/software (including players, video
editors, etc.)</P>
<P>If you enable resizing of the recording the next page has the settings for
choosing the final resolution. MythTV will scale the video as appropriate,
not crop it to this resolution.</P>
<P>The final two pages allow configuration of the video and audio codecs.
Although RTjpeg is an option for video codec there is no reason to transcode
<EM>to</EM> this format because it will produce larger files than MPEG-4 and
the recording will take <EM>more</EM> CPU power to play back. The MPEG-4
settings are described in the documentation for the <B>ffmpeg</B> project
at
<A HREF="http://ffmpeg.sourceforge.net/ffmpeg-doc.html">http://ffmpeg.sourceforge.net/ffmpeg-doc.html</A>. It's a matter of
trial and error to discover which settings achieve a good compromise between
size and quality.</P>
<P>If you wish to return to the default settings, they are Bitrate: 2200-2500,
MaxQ: 2, MinQ: 15, MaxQDiff: 3, and "Scale bitrate for frame size" is
enabled. The other options are unchecked. </P>
<H3>Create/Alter Scheduled Recordings to Enable Transcoding</H3>
<P>Transcoding is actually enabled on a per-recording basis. Two things
must be true before any given recording will be auto-transcoded, however.
The first is that the recording must have been made with a recording profile
that has auto-transcode enabled. Under "Storage Options" for the recording
you must set the "Record using the "X" profile" to the profile you
configured in the first step. In addition, under the "Post Recording
Options" section of the recording you must also set "Transcode new
recordings." This is also where you specify the Transcoding profile to use
(Auto, High, Medium, Low.)</P>
<P>It may not be obvious from above but the flexibility of this system is
primarily to make it possible to auto-transcode a show recorded via one
source (ie: pcHDTV 3000), and not transcode that same show if it's recorded
on another kind of card (ie: PVR-250.) There are other uses however. You
could have a PVR-250 and a V4L card. You may want to transcode the MPEG-2
from the PVR-250 but there is no need to transcode the recordings made with
the V4L card, as it's already likely to be MPEG-4.</P>
<P>As an example, you could configure the Default profile for "Hardware DVB
Encoders" (the profile group used for DVB cards, including ATSC cards like
the pcHDTV 3000) to "Enable auto-transcoding". In the Default profile for
MPEG-2 Encoders (PVR cards) you'd leave "Enable auto-transcoding" unchecked.
For programs that are available on both kinds of cards you'd set the
recording profile to Default and enable auto-transcoding in the record
settings. Then you pick your transcoding profile. The result is that when
a program is recorded on your DVB card, it will get transcoded. When it
plays on a channel available via your PVR card, it won't be.</P>
<H3>Manual Transcoding</H3>
<P>Manually transcoding is activated while watching a show by hitting 'x',
from the OSD menu by choosing the Transcode option, or by choosing Job
Options/Transcode from the info menu from the Watch or Delete
Recordings screens.</P>
<P>The transcoding profile used for manual transcoding is whatever was set when
the recording was originally configured, even if you didn't enable
auto-transcoding. The only way to change what transcoding profile will be
used is to alter the transcoder column in the recorded table in the
database. The transcoder column contains a number which corresponds with
the id column in the recordingprofiles table. You can find out the id
number for each profile in the transcoder group with an SQL command like:</P>
<P>
<BLOCKQUOTE><CODE>
<PRE>
mysql> select r.* from recordingprofiles r,profilegroups p where p.name='Transcoders' and p.id=r.profilegroup;
+----+----------------+------------+------------+--------------+
| id | name | videocodec | audiocodec | profilegroup |
+----+----------------+------------+------------+--------------+
| 21 | RTjpeg/MPEG4 | MPEG-4 | MP3 | 6 |
| 22 | MPEG2 | MPEG-4 | MP3 | 6 |
| 27 | High Quality | MPEG-4 | MP3 | 6 |
| 28 | Medium Quality | MPEG-4 | MP3 | 6 |
| 29 | Low Quality | MPEG-4 | MP3 | 6 |
+----+----------------+------------+------------+--------------+
5 rows in set (0.01 sec)
mysql>
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>Armed with the knowledge of what the profile ID's are you can also choose to
run mythtranscode from the command line and explicitly specify the transcoder
profile. Run <CODE>mythtranscode --help</CODE> for usage information.</P>
<H2><A NAME="ss23.15">23.15</A> <A HREF="mythtv-HOWTO.html#toc23.15">Changing your hostname</A>
</H2>
<P>If you need to change the name of the computers used with MythTV you'll
need to perform a sequence of steps. There are a number of pieces of
information that MythTV keeps track of which are tied to the hostname of the
box, so changing the hostname involves altering the name in the
operating system and in the MySQL database. In the examples below, the old
name of the system was "frontend1" and we're going to change it to
"kidsroom".</P>
<P>
<FIGURE>
<EPS FILE="stop.eps">
<IMG SRC="stop.png">
<CAPTION><B>NOTE</B>: Changing the hostname using direct SQL update commands will
break things. You <EM>MUST</EM> use this indirect method.</CAPTION>
</FIGURE>
</P>
<P>1. Stop all backends. If you run <B>mythbackend</B> from a terminal
session, press control-c. If your backends are started with an init
script, you would do something like the following:
<BLOCKQUOTE><CODE>
<PRE>
$ su
# /etc/init.d/mythbackend stop
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>2. Change the hostname.</P>
<P>For Red Hat and derived distributions, edit the
<CODE>/etc/sysconfig/network</CODE> file. Look for
<CODE>HOSTNAME=frontend1</CODE> and change this to
<CODE>HOSTNAME=kidsroom</CODE> or whatever you'll be using. For other
distributions, refer to the documentation, such as the
<PRE>
hostname(1)
</PRE>
man page.</P>
<P>To alter the
hostname in the current session, run:
<BLOCKQUOTE><CODE>
<PRE>
# hostname kidsroom
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>3. Dump the database.
<BLOCKQUOTE><CODE>
<PRE>
$ mysqldump -u mythtv -pmythtv mythconverg -c > mythtv_backup.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>4. Rename the host in the database. First, ensure that the new hostname
you'll be using isn't already in the database.
<BLOCKQUOTE><CODE>
<PRE>
$ grep kidsroom mythtv_backup.sql
</PRE>
</CODE></BLOCKQUOTE>
Now we're actually going to change the name. The following should all be
typed on the same line:
<BLOCKQUOTE><CODE>
<PRE>
$ cat mythtv_backup.sql | sed s/\'frontend1\'/\'kidsroom\'/g >> mythtv_restore.sql
</PRE>
</CODE></BLOCKQUOTE>
If you don't feel comfortable using <B>sed</B>, you can open the
<CODE>mythtv_backup.sql</CODE> file in a text editor and perform a global search
and replace. When saving the file, make sure you use the new name,
<CODE>mythtv_restore.sql</CODE> or the rest of the steps below will fail.</P>
<P>5. Drop and recreate the database.
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u root
mysql>drop database mythconverg;
mysql>create database mythconverg;
mysql>exit
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>6. Restore the database using your edited version.
<BLOCKQUOTE><CODE>
<PRE>
$ mysql -u mythtv -pmythtv mythconverg < mythtv_restore.sql
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>If you are running slave backends or frontends, don't forget to re-enable
access as detailed in
<A HREF="mythtv-HOWTO-6.html#modify_perm_mysql">Modifying access to the MySQL database for multiple systems</A>. </P>
<P>7. Start the backends. If you use init scripts, do the following, otherwise
start them from terminal consoles.
<BLOCKQUOTE><CODE>
<PRE>
# /etc/init.d/mythbackend start
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>8. Quit and restart all frontends. Delete the <CODE>mythtv_backup.sql</CODE>
and <CODE>mythtv_restore.sql</CODE> files.</P>
<H2><A NAME="ss23.16">23.16</A> <A HREF="mythtv-HOWTO.html#toc23.16">Can I run MythTV on my TiVo?</A>
</H2>
<H2><A NAME="ss23.17">23.17</A> <A HREF="mythtv-HOWTO.html#toc23.17">Can I run MythTV on my ReplayTV?</A>
</H2>
<P>No.</P>
<P>While it is true that the TiVo runs the Linux kernel, and TiVo has released
their changes to the kernel under the GPL, the TiVo is <EM>not</EM> a
general-purpose computer, and there is no programming information available
for the custom hardware contained within a TiVo. TiVo is under no
obligation to release the source code to their <EM>application</EM>.</P>
<P>The ReplayTV runs VxWorks, a Real Time Operating System from Wind River
Systems.</P>
<H2><A NAME="ss23.18">23.18</A> <A HREF="mythtv-HOWTO.html#toc23.18">Can a wireless connection be used between the frontend and the backend?</A>
</H2>
<P>Yes, assuming that your wireless connection has sufficient bandwidth to
maintain the datarate between the frontend and the backend. 802.11b should
be sufficient if the encoded bitrate of the content is less than the
datarate of your wireless connection, which in the case of 802.11b would be
approximately 4 Mbps. (The advertised rate of 11Mbps gives an actual
throughput of 4 Mbps.) 802.11a and 802.11g, if operating in their high-speed
modes, or proprietary 802.11b "Turbo" schemes should be adequate. Multiple
wireless frontends, poor signal strength or other factors can severely
impact the viewing experience on the frontend.</P>
<H2><A NAME="ss23.19">23.19</A> <A HREF="mythtv-HOWTO.html#toc23.19">How can I burn shows that I have recorded to a DVD?</A>
</H2>
<P>There are two answers to this question. The easiest thing to do is to
simply burn the MythTV files onto the DVD and treat the DVD as if it were a
hard drive. This will allow you to save the programs, but it's likely that
they will <EM>not</EM> be playable in a DVD player because the disc will
simply contain files and not any DVD structure. If you'd like to create a
DVD that will play in a standard DVD player and your files have been
recorded as MPEG-2 from a device supported by the IVTV driver, the first
step you'll need to perform is to remux the file to make it DVD compliant.
Next, you'll use <B>dvdauthor</B>, <B>mkisofs</B> to create the ISO
image, and finally <B>dvdrecord</B> to burn that to a blank DVD-R.</P>
<P>The requirements for this procedure are <B>mjpegtools</B> (provides
<B>mplex</B>) and <B>dvdauthor</B> (provides <B>mpeg2desc</B> and
<B>dvdauthor</B>).</P>
<P>This script will perform the necessary steps. You'll need to pass it the
.nuv file and a name for the new DVD project. You should end up with a
directory which you can <B>mkisofs</B> into a ISO file then burn it.</P>
<P>
<BLOCKQUOTE><CODE>
<PRE>
#!/bin/sh
mkfifo aud0
mkfifo vid0
mkfifo dvdmpg
mpeg2desc -a0 < $1 > aud0 &
mpeg2desc -v0 < $1 > vid0 &
mplex -f 8 -V -o dvdmpg aud0 vid0 &