libmpcodecs/ad_libmad.c

   1 // SAMPLE audio decoder - you can use this file as template when creating new codec!
   2
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <unistd.h>
   6
   7 #include "config.h"
   8
   9 #include "ad_internal.h"
  10
  11 static ad_info_t info =  {
  12         "libmad mpeg audio decoder",
  13         "libmad",
  14         "A'rpi",
  15         "libmad...",
  16         "based on Xine's libmad/xine_decoder.c"
  17 };
  18
  19 LIBAD_EXTERN(libmad)
  20
  21 #include <mad.h>
  22
  23 typedef struct mad_decoder_s {
  24
  25   struct mad_synth  synth;
  26   struct mad_stream stream;
  27   struct mad_frame  frame;
  28
  29   int have_frame;
  30
  31   int               output_sampling_rate;
  32   int               output_open;
  33   int               output_mode;
  34
  35 } mad_decoder_t;
  36
  37 static int preinit(sh_audio_t *sh){
  38
  39   mad_decoder_t *this = (mad_decoder_t *) malloc(sizeof(mad_decoder_t));
  40   memset(this,0,sizeof(mad_decoder_t));
  41   sh->context = this;
  42
  43   mad_synth_init  (&this->synth);
  44   mad_stream_init (&this->stream);
  45   mad_frame_init  (&this->frame);
  46
  47   sh->audio_out_minsize=2*4608;
  48   sh->audio_in_minsize=4096;
  49
  50   return 1;
  51 }
  52
  53 static int read_frame(sh_audio_t *sh){
  54   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  55   int len;
  56
  57 while((len=demux_read_data(sh->ds,&sh->a_in_buffer[sh->a_in_buffer_len],
  58           sh->a_in_buffer_size-sh->a_in_buffer_len))>0){
  59   sh->a_in_buffer_len+=len;
  60   while(1){
  61     int ret;
  62     mad_stream_buffer (&this->stream, sh->a_in_buffer, sh->a_in_buffer_len);
  63     ret=mad_frame_decode (&this->frame, &this->stream);
  64     if (this->stream.next_frame) {
  65         int num_bytes =
  66             (char*)sh->a_in_buffer+sh->a_in_buffer_len - (char*)this->stream.next_frame;
  67         memmove(sh->a_in_buffer, this->stream.next_frame, num_bytes);
  68         mp_msg(MSGT_DECAUDIO,MSGL_DBG2,"libmad: %d bytes processed\n",sh->a_in_buffer_len-num_bytes);
  69         sh->a_in_buffer_len = num_bytes;
  70     }
  71     if (ret == 0) return 1; // OK!!!
  72     // error! try to resync!
  73     if(this->stream.error==MAD_ERROR_BUFLEN) break;
  74   }
  75 }
  76 mp_msg(MSGT_DECAUDIO,MSGL_INFO,"Cannot sync MAD frame\n");
  77 return 0;
  78 }
  79
  80 static int init(sh_audio_t *sh){
  81   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  82
  83   this->have_frame=read_frame(sh);
  84   if(!this->have_frame) return 0; // failed to sync...
  85
  86   sh->channels=(this->frame.header.mode == MAD_MODE_SINGLE_CHANNEL) ? 1 : 2;
  87   sh->samplerate=this->frame.header.samplerate;
  88   sh->i_bps=this->frame.header.bitrate/8;
  89   sh->samplesize=2;
  90
  91   return 1;
  92 }
  93
  94 static void uninit(sh_audio_t *sh){
  95   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  96   mad_synth_finish (&this->synth);
  97   mad_frame_finish (&this->frame);
  98   mad_stream_finish(&this->stream);
  99   free(sh->context);
 100 }
 101
 102 /* utility to scale and round samples to 16 bits */
 103 static inline signed int scale(mad_fixed_t sample) {
 104   /* round */
 105   sample += (1L << (MAD_F_FRACBITS - 16));
 106
 107   /* clip */
 108   if (sample >= MAD_F_ONE)
 109     sample = MAD_F_ONE - 1;
 110   else if (sample < -MAD_F_ONE)
 111     sample = -MAD_F_ONE;
 112
 113   /* quantize */
 114   return sample >> (MAD_F_FRACBITS + 1 - 16);
 115 }
 116
 117 static int decode_audio(sh_audio_t *sh,unsigned char *buf,int minlen,int maxlen){
 118   mad_decoder_t *this = (mad_decoder_t *) sh->context;
 119   int len=0;
 120
 121   while(len<minlen && len+4608<=maxlen){
 122     if(!this->have_frame) this->have_frame=read_frame(sh);
 123     if(!this->have_frame) break; // failed to sync... or EOF
 124     this->have_frame=0;
 125
 126     mad_synth_frame (&this->synth, &this->frame);
 127
 128         { unsigned int         nchannels, nsamples;
 129           mad_fixed_t const   *left_ch, *right_ch;
 130           struct mad_pcm      *pcm = &this->synth.pcm;
 131           uint16_t            *output = (uint16_t*) buf;
 132
 133           nchannels = pcm->channels;
 134           nsamples  = pcm->length;
 135           left_ch   = pcm->samples[0];
 136           right_ch  = pcm->samples[1];
 137
 138           len+=2*nchannels*nsamples;
 139           buf+=2*nchannels*nsamples;
 140
 141           while (nsamples--) {
 142             /* output sample(s) in 16-bit signed little-endian PCM */
 143
 144             *output++ = scale(*left_ch++);
 145
 146             if (nchannels == 2)
 147               *output++ = scale(*right_ch++);
 148
 149           }
 150         }
 151   }
 152
 153   return len?len:-1;
 154 }
 155
 156 static int control(sh_audio_t *sh,int cmd,void* arg, ...){
 157   mad_decoder_t *this = (mad_decoder_t *) sh->context;
 158     // various optional functions you MAY implement:
 159     switch(cmd){
 160       case ADCTRL_RESYNC_STREAM:
 161         this->have_frame=0;
 162         mad_synth_init  (&this->synth);
 163         mad_stream_init (&this->stream);
 164         mad_frame_init  (&this->frame);
 165         return CONTROL_TRUE;
 166       case ADCTRL_SKIP_FRAME:
 167         this->have_frame=read_frame(sh);
 168         return CONTROL_TRUE;
 169     }
 170   return CONTROL_UNKNOWN;
 171 }