[mythtv-users] Problem: 4:3 content always fills my 15:9 screen. Consequently, the aspect ratio is incorrect.

Christopher David Petersen christopher.david.petersen at gmail.com
Wed Oct 10 22:31:26 UTC 2007

Let me first apologize if this problem has already been discussed and
solved. I have searched the lists and web, but have not found the
solution (or I'm too ignorant to recognize the solution when I see

The problem is that 4:3 content always fills my 15:9 screen and
therefore the aspect ratio is always incorrect.

I have a fresh install of MythDora 4.0 on an original Asus Pundit-S
(SiS 651 video chipset). To enable SchedulesDirect support, I have run
the following command (per the advice given here
http://g-ding.tv/?q=node/2191) :

# yum upgrade \*myth\*

The display is an Olevia by Syntax LT26HVE LCD TV. I'm using DVI to
connect it to the Pundit. The LT26HVE has a native resolution of
1280x768 and its screen dimensions are 570mm x 342mm. Both the
dimensions and resolution indicate a 15:9 aspect ratio with square
pixels. The LT26HVE does have various aspect ratio controls, but they
are only available for configuration when the LT26HVE is using its
internal NTSC tuner.

The documentation for the LT26HVE indicates the following:

PC compatible frequency: 30-85 KHz(H) / 50-80Hz(V) Max. 1280x1024 at 60Hz
[not the native resolution of 1280x768, apparently it can compress
images vertically (this may be important, but I doubt it) ].

When source = DVI:
            Resolution: 1280x768
            Vertical Frequency (Hz): 60
            Horizontal Frequency (KHz): 48.36
            Pixel rate (MHz): 81.631

Using this information, I generated the following ModeLine using the
"The XFree86 Modeline Generator"
Modeline "1280x768 at 60" 79.75 1280 1312 1608 1640 768 783 791 807

I have modified (by hand) my /etc/X11/xorg.conf to use this Modeline
and to set the DisplaySize:

# Xorg configuration created by system-config-display
Section "ServerLayout"
      Identifier     "single head configuration"
      Screen      0  "Screen0" 0 0
      InputDevice    "Keyboard0" "CoreKeyboard"

Section "InputDevice"
      Identifier  "Keyboard0"
      Driver      "kbd"
      Option          "XkbModel" "pc105"
      Option          "XkbLayout" "us"

Section "Monitor"
      Identifier   "LT26HVE"
      VendorName   "Olevia"
      ModelName    "LT26HVE"
      DisplaySize  570  342
      HorizSync    30.0 - 85.0
      VertRefresh  50.0 - 80.0
      ModeLine     "1280x768 at 60" 79.8 1280 1312 1608 1640 768 783 791 807

Section "Device"
      Identifier  "Videocard0"
      Driver      "sis"

Section "Screen"
      Identifier "Screen0"
      Device     "Videocard0"
      Monitor    "LT26HVE"
      DefaultDepth     24
      SubSection "Display"
            Viewport   0 0
            Depth     24
            Modes "1280x768 at 60"

The LT26HVE's on-screen menu (not MythTV's on-screen menu) indicates
it is receiving a 1280x768 signal from the DVI port.

The user interface in MythTV looks beautiful: aspect ratio of circles
is correct (when physically measured with a ruler on the screen). DVD
playback looks great: aspect ratio of Universal Studio's logo (the
rotating Earth) is correct (again, physically measured on the screen).

However, the aspect ratio of content captured using my PVR-250 card
(LiveTV or Recordings) is not correct. The image is stretched to fill
the whole screen. I have the PVR-250 set to capture at 720x480 (3:2
aspect ratio), but I've indicated in the Recording Profiles that the
aspect ratio is 4:3. I have not indicated an aspect ratio override in
the TV->Playback settings.

Pressing the "W" key (or changing the aspect ratio during playback by
using MythTVs on-screen menu) exhibits the following behavior: "None",
"4:3", and "Fill" all look exactly the same. The image fills the
screen and the aspect ratio is incorrect (the image is stretched

The following is a list of un-successful experiments I have tried:

Experiment #1: Pressing "W" during playback.
Result: Aspect ratios "None", "4:3", and "Fill" all look the same: the
image is stretched horizontally to fill the screen. The aspect ratio
is incorrect.

Experiment #2: Indicating an aspect override of 4:3 in TV->Playback.
Result: PVR-250 captured content is still horizontally stretched to
fill the whole screen.
Analysis: I wasn't really expecting this to work because it's the same
as changing the Aspect Ratio to 4:3 (by pressing "W").

Experiment #3: Changing the aspect ratio on the capture card in
(Settings->TV->Recording Profiles)
Result: PVR-250 captured content is still horizontally stretched to
fill the whole screen, and the aspect ratio is incorrect regardless of
which aspect ratio I choose.
Analysis: This incorrect behavior doesn't surprise me, because there's
no way to stretch 4:3 content into a 15:9 window while maintaining the
proper aspect ratio.

Experiment #4: Changing the PVR-250's capture resolution to 640x480 (a
4:3 ratio).
Result: PVR-250 captured content is still horizontally stretched to
fill the whole screen, and the aspect ratio is incorrect.
Analysis: Again, if the 4:3 content fills the 15:9 screen, the aspect
ratio will be incorrect.

Experiment #5: Setting Option "IgnoreEDID" "true" in the xorg.conf
file for "VideoCard0".
Result: 4:3 content fills the 15:9 screen, the aspect ratio is incorrect.
Analysis: My thinking for this experiment was that the LT26HVE was
incorrectly reporting via EDID that it is a 4:3 display device. MythTV
was seeing this information and consequently filling the whole
1280x768 screen (thinking it had a 4:3 aspect ratio).

Experiment #6: Setting the DisplaySize in the xorg.conf file to
indicate a 100x100 dpi resolution. Many posts indicate that this is
required for MythTV to size GUI elements properly (although I have not
seen any improperly sized GUI elements in any of my previous
Result: No change in the improper behavior. 4:3 content fills the 15:9
screen, and the aspect ratio is incorrect.
Analysis: I wasn't expecting this to work, because it solves a
different problem (improperly sized GUI elements) which I haven't

Does anybody have any advice on how to get 4:3 content to display with
the proper aspect ratio (which would mean black bars on the sides)?

I'm open to many suggestions (including re-installs and potentially
system breaking experiments).

More information about the mythtv-users mailing list