Back to basics

Back to basics

[Richard Jones]

Hi all

I have what I am hoping is a very basic question and the answer will 
help me better understand ALSA and how it works.

What I want to do is write a simple program that lists the available 
midi devices currently connected to my machine and I can then choose one 
and capture the input from that midi device.

I think it best to break it down into the components

1. I connect my Yamaha keyboard to my laptop and it is assigned to one 
of the midi devices in /dev/snd/midi????. Is there a way with ALSA to 
list the devices that are currently valid or a way of working it out in 
a program. I have seen "pmidi -l" but that gives me a list of ports that 
I don't know how to relate back to the device names in /dev/snd. 
Similarly, rawmidi requires me to know which device has been allocated 
to my keyboard. I have seen music applications using ALSA that produce a 
pull down list of valid devices to choose from. How do they work that out?

2. I want to read the midi stream coming in from the piano and just 
translate it into its relative note value - middle C. (using the ALSA API)

So, ignoring all error handling and other programming "stuff", could 
someone please write down the most basic piece of C code where the ALSA 
API is being used to achieve these two things?

Thanks
Bob



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