audio_oss_sink.cc

这是用python语言写的一个数字广播的信号处理工具包。利用它

/* -*- c++ -*- */
/*
 * Copyright 2004 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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <audio_oss_sink.h>
#include <gr_io_signature.h>
#include <gr_prefs.h>
#include <sys/soundcard.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <iostream>
#include <stdexcept>


static std::string
default_device_name ()
{
  return gr_prefs::singleton()->get_string("audio_oss", "default_output_device", "/dev/dsp");
}

audio_oss_sink_sptr
audio_oss_make_sink (int sampling_rate, const std::string dev, bool ok_to_block)
{
  return audio_oss_sink_sptr (new audio_oss_sink (sampling_rate, dev, ok_to_block));
}

audio_oss_sink::audio_oss_sink (int sampling_rate,
				const std::string device_name,
				bool ok_to_block)
  : gr_sync_block ("audio_oss_sink",
		   gr_make_io_signature (1, 2, sizeof (float)),
		   gr_make_io_signature (0, 0, 0)),
    d_sampling_rate (sampling_rate),
    d_device_name (device_name.empty() ? default_device_name() : device_name),
    d_fd (-1), d_buffer (0), d_chunk_size (0)
{
  if ((d_fd = open (d_device_name.c_str (), O_WRONLY)) < 0){
    fprintf (stderr, "audio_oss_sink: ");
    perror (d_device_name.c_str ());
    throw std::runtime_error ("audio_oss_sink");
  }

  double CHUNK_TIME = 
    std::max(0.001, gr_prefs::singleton()->get_double("audio_oss", "latency", 0.005));

  d_chunk_size = (int) (d_sampling_rate * CHUNK_TIME);
  set_output_multiple (d_chunk_size);

  d_buffer = new short [d_chunk_size * 2];

  int format = AFMT_S16_NE;
  int orig_format = format;
  if (ioctl (d_fd, SNDCTL_DSP_SETFMT, &format) < 0){
    std::cerr << "audio_oss_sink: " << d_device_name << " ioctl failed\n";
    perror (d_device_name.c_str ());
    throw std::runtime_error ("audio_oss_sink");
  }

  if (format != orig_format){
    fprintf (stderr, "audio_oss_sink: unable to support format %d\n", orig_format);
    fprintf (stderr, "  card requested %d instead.\n", format);
  }

  // set to stereo no matter what.  Some hardware only does stereo
  int channels = 2;
  if (ioctl (d_fd, SNDCTL_DSP_CHANNELS, &channels) < 0 || channels != 2){
    perror ("audio_oss_sink: could not set STEREO mode");
    throw std::runtime_error ("audio_oss_sink");
  }

  // set sampling freq
  int sf = sampling_rate;
  if (ioctl (d_fd, SNDCTL_DSP_SPEED, &sf) < 0){
    std::cerr << "audio_oss_sink: "
	      << d_device_name << ": invalid sampling_rate "
	      << sampling_rate << "\n";
    sampling_rate = 8000;
    if (ioctl (d_fd, SNDCTL_DSP_SPEED, &sf) < 0){
      std::cerr << "audio_oss_sink: failed to set sampling_rate to 8000\n";
      throw std::runtime_error ("audio_oss_sink");
    }
  }
}

audio_oss_sink::~audio_oss_sink ()
{
  close (d_fd);
  delete [] d_buffer;
}


int
audio_oss_sink::work (int noutput_items,
		      gr_vector_const_void_star &input_items,
		      gr_vector_void_star &output_items)
{
  const float  *f0, *f1;
  
  switch (input_items.size ()){

  case 1:		// mono input

    f0 = (const float *) input_items[0];

    for (int i = 0; i < noutput_items; i += d_chunk_size){
      for (int j = 0; j < d_chunk_size; j++){
	d_buffer[2*j+0] = (short) (f0[j] * 32767);
	d_buffer[2*j+1] = (short) (f0[j] * 32767);
      }
      f0 += d_chunk_size;
      if (write (d_fd, d_buffer, 2 * d_chunk_size * sizeof (short)) < 0)
	perror ("audio_oss_sink: write");
    }
    break;
    
  case 2:		// stereo input

    f0 = (const float *) input_items[0];
    f1 = (const float *) input_items[1];

    for (int i = 0; i < noutput_items; i += d_chunk_size){
      for (int j = 0; j < d_chunk_size; j++){
	d_buffer[2*j+0] = (short) (f0[j] * 32767);
	d_buffer[2*j+1] = (short) (f1[j] * 32767);
      }
      f0 += d_chunk_size;
      f1 += d_chunk_size;
      if (write (d_fd, d_buffer, 2 * d_chunk_size * sizeof (short)) < 0)
	perror ("audio_oss_sink: write");
    }
    break;
  }

  return noutput_items;
}