[mythtv-users] Legibility from the sofa

Robert Koblish rkoblish at gmail.com
Wed Feb 17 02:04:45 UTC 2010

I've been dealing with issues of legibility from the couch also. I
think I've had some success. Perhaps some of my findings will be
useful to others.

I've been using Mythtv on-and-off since version 0.17 or so. Now I am
getting serious about setting it up for the family to use. I have been
using the MythCenter theme. The menus are legible when viewed on the
computer's screen at a normal distance. But legibility from the couch
was an issue. Beyond the 10-foot problem itself, I am using a ~20
years old NTSC TV driven with Svideo from an Nvidia FX5200 card.
Because of the limited frequency response of the TV, even over Svideo,
the smaller characters were blurry and hard to read. Also I noticed
that in both Mythcenter and the default theme, some of the text was
truncated. In most screens this is not a problem, but it would reduce
the WAF when one recording rule (there is more than one that begins
"record at any time...") could not be distinguished from another.

Also, it seemed that not all themes worked well with all combinations
of the available date and time formats. In particular, when I was
using the default font with a date format like "Sun 02/14" and an
AM/PM time format, it was not possible to distinguish between 1:00 pm
and 11:00 pm in the watch recordings screen because the tens digit of
the hour was cut off.

So I investigated the theme's layout, font usage, etc. I noticed that
even though MythCenter calls for a different typeface (Trebuchet MS)
from the default (DejaVu Sans), all of the menus in Mythcenter were
displayed in the default font. I discovered that Trebuchet MS was not
installed on my frontend.  (I looked at the logs, but did not see any
complaint in them that the font requested by the theme was not
available. Perhaps I didn't look in the right place, or with the
correct set of logging options enabled.)

I installed the MS Core Truetype font package. Now the main menus were
displayed in Trebuchet (it's easiest for me to tell Trebuchet from
DejaVu Sans based on the shape of the lowercase 'g' and the digit
'1'). But other screens were still displayed in DejaVu Sans, and the
same problems with text too big for its space persisted in those
screens. I made a copy of the MythCenter theme to experiment on --
call it MythCenter-test. After reading the theming documentation I
discovered that if I copied the first of the base font definitions
/usr/share/mythtv/themes/MythCenter-test/base.xml, that all of the
screens would use the Trebuchet font.
The text I copied was
   <!-- Base Font Definitions -->
   <font name="basesmall" face="Trebuchet MS">

I also changed the font definitions in base.xml to inherit their names
from basesmall -- for example:
<!-- this is the line I removed
       <font name="small" face="Trebuchet MS">
       <font name="small" from="basesmall">

I made a similar change in menu-ui.xml.

Now all the menus use the same typeface, so they have a consistent
appearance, and I can change the base font by editing a single line in
my base.xml file.


I did some further experimentation in the interest of legibility. I
considered trying Verdana, which I read was designed for good
legibility on the screen. But then I recalled taking a tour of the NBC
studios years ago, and observing that the typeface used in their title
cards had characters that were distorted to precompensate for the
limited resolution of the broadcast video encoding and of home
receivers. Among the font's salient characteristics was this: the
inside corners of the glyphs had small-radius arcs cut out of them
instead of the strokes just meeting at a point. By the time the signal
passed through the broadcast video chain and into the receiver, the
cutouts were invisible and the corners of the characters looked as
crisp as possible. I started looking for Truetype fonts that had this
same characteristic.

I did not come across any video titling fonts per se, but I did
stumble across a family of fonts called Bell Century. These were
developed in the late 1960s for use by the Bell System telephone
companies. They were aimed at improving the legibility of small
characters printed on cheap paper in the telephone directory. The
glyphs were designed with large center holes, large gaps between
characters, and ink traps cut out at the inside corners, all aimed at
minimizing the tendency for ink spread to reduce the legibility of the
characters. I reasoned that the ink spread acts as a low-pass filter
similarly to the NTSC video encoding, so a typeface designed to be
legible in small sizes on paper might work well in video. I am happy
with the results; I never did get around to trying Verdana. And
because the characters are narrower than those of the default font,
all the text now fits within its designated column or box. The only
drawback I've found is the lack of a glyph for the '%' sign, which is
used in some of the On-Screen Displays.

I am not sure of the legal or copyright status of the Bell Century
fonts. I found some web sites that want to sell them, and a couple
that would let me download them at no cost. This may or may not be an
issue in your jurisdiction.

Does anyone know of a free font designed for video titling, or
optimized for good legibility at small resolutions?

Bob Koblish

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