libao2/ao_null.c

   1 /*
   2  * null audio output driver
   3  *
   4  * This file is part of MPlayer.
   5  *
   6  * MPlayer is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * MPlayer is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <sys/time.h>
  24
  25 #include "config.h"
  26 #include "libaf/af_format.h"
  27 #include "audio_out.h"
  28 #include "audio_out_internal.h"
  29
  30 static ao_info_t info =
  31 {
  32         "Null audio output",
  33         "null",
  34         "Tobias Diedrich <ranma+mplayer@tdiedrich.de>",
  35         ""
  36 };
  37
  38 LIBAO_EXTERN(null)
  39
  40 struct  timeval last_tv;
  41 int     buffer;
  42
  43 static void drain(void){
  44
  45     struct timeval now_tv;
  46     int temp, temp2;
  47
  48     gettimeofday(&now_tv, 0);
  49     temp = now_tv.tv_sec - last_tv.tv_sec;
  50     temp *= ao_data.bps;
  51
  52     temp2 = now_tv.tv_usec - last_tv.tv_usec;
  53     temp2 /= 1000;
  54     temp2 *= ao_data.bps;
  55     temp2 /= 1000;
  56     temp += temp2;
  57
  58     buffer-=temp;
  59     if (buffer<0) buffer=0;
  60
  61     if(temp>0) last_tv = now_tv;//mplayer is fast
  62 }
  63
  64 // to set/get/query special features/parameters
  65 static int control(int cmd,void *arg){
  66     return -1;
  67 }
  68
  69 // open & setup audio device
  70 // return: 1=success 0=fail
  71 static int init(int rate,int channels,int format,int flags){
  72
  73     int samplesize = af_fmt2bits(format) / 8;
  74     ao_data.outburst = 256 * channels * samplesize;
  75     // A "buffer" for about 0.2 seconds of audio
  76     ao_data.buffersize = (int)(rate * 0.2 / 256 + 1) * ao_data.outburst;
  77     ao_data.channels=channels;
  78     ao_data.samplerate=rate;
  79     ao_data.format=format;
  80     ao_data.bps=channels*rate*samplesize;
  81     buffer=0;
  82     gettimeofday(&last_tv, 0);
  83
  84     return 1;
  85 }
  86
  87 // close audio device
  88 static void uninit(int immed){
  89
  90 }
  91
  92 // stop playing and empty buffers (for seeking/pause)
  93 static void reset(void){
  94     buffer=0;
  95 }
  96
  97 // stop playing, keep buffers (for pause)
  98 static void audio_pause(void)
  99 {
 100     // for now, just call reset();
 101     reset();
 102 }
 103
 104 // resume playing, after audio_pause()
 105 static void audio_resume(void)
 106 {
 107 }
 108
 109 // return: how many bytes can be played without blocking
 110 static int get_space(void){
 111
 112     drain();
 113     return ao_data.buffersize - buffer;
 114 }
 115
 116 // plays 'len' bytes of 'data'
 117 // it should round it down to outburst*n
 118 // return: number of bytes played
 119 static int play(void* data,int len,int flags){
 120
 121     int maxbursts = (ao_data.buffersize - buffer) / ao_data.outburst;
 122     int playbursts = len / ao_data.outburst;
 123     int bursts = playbursts > maxbursts ? maxbursts : playbursts;
 124     buffer += bursts * ao_data.outburst;
 125     return bursts * ao_data.outburst;
 126 }
 127
 128 // return: delay in seconds between first and last sample in buffer
 129 static float get_delay(void){
 130
 131     drain();
 132     return (float) buffer / (float) ao_data.bps;
 133 }