On an i.MX6Q embedded Linux device, I have an application with two different video modes available: 1280x1024 and 800x600. Here are the mode specs from /etc/fb.modes:
mode "1280x1024 60Hz 24bit"
# D: 107.99 MHz, H: 64.281 KHz, V: 60.08 Hz
geometry 1280 1024 1280 5120 24
timings 9260 128 128 40 2 144 4
mode "800x600 59Hz 24bit"
# D: 41.38 MHz, H: 37.754 kHz, V: 59.93 Hz
geometry 800 600 1280 5120 24
timings 22727 128 96 24 2 144 4
When I use the speaker test to generate a sine wave, e.g. using:
speaker-test -D plughw:0,0 --test sine
(Note: in my hardware/kernel HDMI is the only audio device.)
I get a different tone (pitch/frequency) depending on which video mode is selected, even though the speaker test is supposed to generate a default frequency of 440 Hz (music note A4) for the sine wave. The difference between the two in the different video modes is easily noticeable. Off hand, I'm not sure if or which one is correct.
Does anyone know why different frequencies are being output?