av/revid/audio_linux.go

/*
LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)

  This is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package revid

import (
	"time"

	"bitbucket.org/ausocean/av/device/alsa"
	"bitbucket.org/ausocean/utils/logger"
)

// startAudioDevice is used to start capturing audio from an ALSA audio device and processing it.
// It returns a function that can be used to stop the device and any errors that occur.
func (r *Revid) startAudioDevice() (func() error, error) {
	// Create audio device.
	ai := alsa.NewALSA(r.cfg.Logger)

	err := ai.Set(r.cfg)
	if err != nil {
		r.cfg.Logger.Log(logger.Fatal, pkg+"failed to setup ALSA device", "error", err.Error())
	}

	// Start ALSA audio device
	err = ai.Start()
	if err != nil {
		r.cfg.Logger.Log(logger.Fatal, pkg+"failed to start ALSA device", "error", err.Error())
	}

	// Process output from ALSA audio device.
	r.cfg.ChunkSize = ai.ChunkSize()
	r.wg.Add(1)
	go r.processFrom(ai, time.Duration(float64(time.Second)/r.cfg.WriteRate))
	return func() error {
		ai.Stop()
		return nil
	}, nil
}