Raspberry Pi A, User Manual, Page: 128 / 314

112
P A R T I
C O N N E C T I N G T H E B O A R D
❍
framebuffer_ignore_alpha —Set to
1
, this value disables the alpha channel , which
controls transparency in the console. Disabling the alpha channel is not normally
required, but it may correct graphical corruption caused when setting
framebuffer_
depth
to 32 bits per pixel.
❍
sdtv_mode— This value affects the analogue composite video output of the Pi, adjust-
ing it to operate in various countries. By default, the Pi uses the North American ver-
sion of the NTSC video standard; users in other countries may need to change this
value to get a picture on an analogue TV. Possible values are:
•
0
—NTSC, the North American video standard
•
1 —NTSC-J, the Japanese video standard
•
2— PAL, the video standard for the UK and other countries
•
3 —PAL-M, the Brazilian video standard
❍
sdtv_aspect—
Controls the aspect ratio of the analogue composite output. If the pic-
ture looks stretched or squished, alter this to correspond to your TV’s aspect ratio.
Possible values are:
•
1
—4:3 aspect ratio, common on older sets
•
2
—14:9 aspect ratio, common for smaller widescreen TVs
•
3
—16:9 aspect ratio, common for modern widescreen TVs
❍
hdmi_mode— In addition to setting the video mode for the analogue composite out-
put, it’s also possible to override automatic resolution detection on the HDMI port.
This is handy if you want to run your Pi at a lower resolution than the display’s native
resolution in order to make things more readable from a distance. Appendix C, “HDMI
Display Modes”, lists the possible values for this setting.
❍
hdmi_drive —It’s also possible to alter the voltage output by the HDMI port. This is
important when you’re using an HDMI to DVI adapter, because HDMI and DVI volt-
ages differ slightly. If you find that your picture is snowy or blown out with too bright
an image, try altering this setting. Possible values are:
•
1 —DVI output voltages. In this mode, no audio is included on the HDMI cable.
•
2
—HDMI output voltages. In this mode, audio is included on the HDMI cable.
❍
hdmi_force_hotplug —Forces the Raspberry Pi to use the HDMI port, even if it
doesn’t detect a connected display. A value of
0
allows the Pi to attempt to detect the
display, while a value of
1
forces the Pi to use HDMI regardless.