In my application the raspi is an embedded device. It uses bluetooth to take an incoming audio stream, WiFi for the control connection, splits the audio stream, puts one stream to an analog amplifier and the second stream is used internally to drive some magnets.
Well, I first used the 3.5mm audio out headphone jack on the raspi to drive the amplifier, but the quality was very poor (as many noticed already). I read in the forums and found two alternatives:
a) a USB sound card
b) using an audio extractor to drive my amplifier (which needs an analog stereo input signal)
Since I already max out the USB interface with WiFi and Bluetooth I decided to use the HDMI output. I bought an HDMI audio extractor and cabled it all up. After a day of tinkering with it I go thus far:
* when I connect a computer monitor (without speakers) to the HDMI out of the extractor, connect the extractor to the raspi, configure alsa and pulse properly, tweak /boot/config.txt, THEN I get crystal clear, loud audio to the speakers. And my magnets are also properly driven.
* the moment I disconnect the monitor from the HDMI out of the extractor, the audio goes silent. It comes back, when I reconnect the monitor.
This is not good enough for me, as this should be embedded and run without a monitor. What do I have to do to make the raspi put audio out the HDMI even if there is no monitor, only the audio extractor, connected to its HDMI output?
Here is what I tried already:
* I made a dump of the edit config while audio was working and saved it to /boot/edid.dat, hoping this working config would then be forced onto the raspi
* I changed the audio devices to HDMI in pulse, alsa, bluetooth
What can I do to make the raspi stream HDMI audio even if only the extractor is plugged into its HDMI port and no monitor is connected?
Thanks a lot