note
	description: "Tools to capture audio from a capturing audio device"
	author: "Louis Marchand"
	date: "Thu, 15 Jun 2017 19:17:55 +0000"
	revision: "0.1"

class interface
	AUDIO_CAPTURE_CONTROLLER

create {AUDIO_LIBRARY_CONTROLLER}
	make

feature -- Access

	is_capturing: BOOLEAN
			-- Current is presently capturing sound

	is_device_closed: BOOLEAN
			-- The capturing device id closed

	channel_count: INTEGER_32
			-- The channel number of Current (1=mono, 2=stereo, etc.).

	frequency: INTEGER_32
			-- The frequency (sample rate) of Current.

	bits_per_sample: INTEGER_32
			-- The bit resolution of one frame of Current (without channel count).

	buffer_sample_count: INTEGER_32
			-- The number of samples that the buffer will be able to contain (for example,
			-- a stereo 16 bits capture with a buffer count of 1024 will have the size 1024*2*2 = 5096 bytes)

	buffer: MANAGED_POINTER
			-- The data that has been read by update

	start_capture
			-- Strart the capture (use update to fill the buffer)
		require
			device_open: not is_device_closed
			not_already_started: not is_capturing
		ensure
			capture_started: not has_error implies is_capturing

	stop_capture
			-- Stop the capture
		require
			device_open: not is_device_closed
			not_already_stopped: is_capturing
		ensure
			captue_stopped: not is_capturing

	update
			-- Update a_buffer with the new value of the capture
		require
			device_open: not is_device_closed
			is_capturing: is_capturing

	has_samples: BOOLEAN
			-- Samples has been found by the last call to update

	get_sample (a_index: INTEGER_32): LIST [INTEGER_16]
			-- Get the sample at the position a_index in the buffer (start at 1).
			-- The number of value in Result represent the channel_count
			-- If bits_per_sample is 8, the values are unsigned from 0 to 255 with 128 being an ouput level of 0
			-- If bits_per_sample is 16, the values are signed from -32768 to 32767 with 0 being an ouput level of 0
		require
			index_valid: a_index >= 1 and a_index <= buffer_sample_count
		ensure
			sample_count_valid: Result.count ~ channel_count
	
invariant
	buffer_count_valid: buffer.count ~ buffer_sample_count * channel_count * (bits_per_sample // 8)

end -- class AUDIO_CAPTURE_CONTROLLER

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