audio_alsa_source.h

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/* -*- c++ -*- */
/*
 * Copyright 2004-2011 Free Software Foundation, Inc.
 * 
 * This file is part of GNU Radio
 * 
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 * 
 * GNU Radio 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
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef INCLUDED_AUDIO_ALSA_SOURCE_H
#define INCLUDED_AUDIO_ALSA_SOURCE_H

// use new ALSA API
#define ALSA_PCM_NEW_HW_PARAMS_API
#define ALSA_PCM_NEW_SW_PARAMS_API

#include <gr_audio_source.h>
#include <string>
#include <alsa/asoundlib.h>
#include <stdexcept>

class audio_alsa_source;
typedef boost::shared_ptr<audio_alsa_source> audio_alsa_source_sptr;

/*!
 * \brief audio source using ALSA
 *
 * The source has between 1 and N input streams of floats, where N is
 * depends on the hardware characteristics of the selected device.
 *
 * Output samples will be in the range [-1,1].
 */
class audio_alsa_source : public audio_source {
  // typedef for pointer to class work method
  typedef int (audio_alsa_source::*work_t)(int noutput_items,
                                           gr_vector_const_void_star &input_items,
                                           gr_vector_void_star &output_items);

  unsigned int          d_sampling_rate;
  std::string           d_device_name;
  snd_pcm_t            *d_pcm_handle;
  snd_pcm_hw_params_t  *d_hw_params;
  snd_pcm_sw_params_t  *d_sw_params;
  snd_pcm_format_t      d_format;
  unsigned int          d_nperiods;
  unsigned int          d_period_time_us;       // microseconds
  snd_pcm_uframes_t     d_period_size;          // in frames
  unsigned int          d_buffer_size_bytes;    // sizeof of d_buffer
  char                 *d_buffer;
  work_t                d_worker;               // the work method to use
  unsigned int          d_hw_nchan;             // # of configured h/w channels
  bool                  d_special_case_stereo_to_mono;

  // random stats
  int                   d_noverruns;            // count of overruns
  int                   d_nsuspends;            // count of suspends

  void output_error_msg (const char *msg, int err);
  void bail (const char *msg, int err) throw (std::runtime_error);

public:
  audio_alsa_source (int sampling_rate, const std::string device_name,
                     bool ok_to_block);

  ~audio_alsa_source ();
  
  bool check_topology (int ninputs, int noutputs);

  int work (int noutput_items,
            gr_vector_const_void_star &input_items,
            gr_vector_void_star &output_items);

protected:
  bool read_buffer (void *buffer, unsigned nframes, unsigned sizeof_frame);

  int work_s16 (int noutput_items,
                gr_vector_const_void_star &input_items,
                gr_vector_void_star &output_items);

  int work_s16_2x1 (int noutput_items,
                    gr_vector_const_void_star &input_items,
                    gr_vector_void_star &output_items);

  int work_s32 (int noutput_items,
                gr_vector_const_void_star &input_items,
                gr_vector_void_star &output_items);

  int work_s32_2x1 (int noutput_items,
                    gr_vector_const_void_star &input_items,
                    gr_vector_void_star &output_items);
};

#endif /* INCLUDED_AUDIO_ALSA_SOURCE_H */