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 #ifdef USE_LIBMAD
  10
  11 #include "ad_internal.h"
  12
  13 static ad_info_t info =  {
  14         "libmad mpeg audio decoder",
  15         "libmad",
  16         "A'rpi",
  17         "libmad...",
  18         "based on Xine's libmad/xine_decoder.c"
  19 };
  20
  21 LIBAD_EXTERN(libmad)
  22
  23 #include <mad.h>
  24
  25 typedef struct mad_decoder_s {
  26
  27   struct mad_synth  synth;
  28   struct mad_stream stream;
  29   struct mad_frame  frame;
  30
  31   int have_frame;
  32
  33   int               output_sampling_rate;
  34   int               output_open;
  35   int               output_mode;
  36
  37 } mad_decoder_t;
  38
  39 static int preinit(sh_audio_t *sh){
  40
  41   mad_decoder_t *this = (mad_decoder_t *) malloc(sizeof(mad_decoder_t));
  42   memset(this,0,sizeof(mad_decoder_t));
  43   sh->context = this;
  44
  45   mad_synth_init  (&this->synth);
  46   mad_stream_init (&this->stream);
  47   mad_frame_init  (&this->frame);
  48
  49   sh->audio_out_minsize=2*4608;
  50   sh->audio_in_minsize=4096;
  51
  52   return 1;
  53 }
  54
  55 static int read_frame(sh_audio_t *sh){
  56   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  57   int len;
  58
  59 while((len=demux_read_data(sh->ds,&sh->a_in_buffer[sh->a_in_buffer_len],
  60           sh->a_in_buffer_size-sh->a_in_buffer_len))>0){
  61   sh->a_in_buffer_len+=len;
  62   while(1){
  63     int ret;
  64     mad_stream_buffer (&this->stream, sh->a_in_buffer, sh->a_in_buffer_len);
  65     ret=mad_frame_decode (&this->frame, &this->stream);
  66     if (this->stream.next_frame) {
  67         int num_bytes =
  68             (char*)sh->a_in_buffer+sh->a_in_buffer_len - (char*)this->stream.next_frame;
  69         memmove(sh->a_in_buffer, this->stream.next_frame, num_bytes);
  70         mp_msg(MSGT_DECAUDIO,MSGL_DBG2,"libmad: %d bytes processed\n",sh->a_in_buffer_len-num_bytes);
  71         sh->a_in_buffer_len = num_bytes;
  72     }
  73     if (ret == 0) return 1; // OK!!!
  74     // error! try to resync!
  75     if(this->stream.error==MAD_ERROR_BUFLEN) break;
  76   }
  77 }
  78 mp_msg(MSGT_DECAUDIO,MSGL_INFO,"Cannot sync MAD frame\n");
  79 return 0;
  80 }
  81
  82 static int init(sh_audio_t *sh){
  83   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  84
  85   this->have_frame=read_frame(sh);
  86   if(!this->have_frame) return 0; // failed to sync...
  87
  88   sh->channels=(this->frame.header.mode == MAD_MODE_SINGLE_CHANNEL) ? 1 : 2;
  89   sh->samplerate=this->frame.header.samplerate;
  90   sh->i_bps=this->frame.header.bitrate/8;
  91   sh->samplesize=2;
  92
  93   return 1;
  94 }
  95
  96 static void uninit(sh_audio_t *sh){
  97   mad_decoder_t *this = (mad_decoder_t *) sh->context;
  98   mad_synth_finish (&this->synth);
  99   mad_frame_finish (&this->frame);
 100   mad_stream_finish(&this->stream);
 101   free(sh->context);
 102 }
 103
 104 /* utility to scale and round samples to 16 bits */
 105 static inline signed int scale(mad_fixed_t sample) {
 106   /* round */
 107   sample += (1L << (MAD_F_FRACBITS - 16));
 108
 109   /* clip */
 110   if (sample >= MAD_F_ONE)
 111     sample = MAD_F_ONE - 1;
 112   else if (sample < -MAD_F_ONE)
 113     sample = -MAD_F_ONE;
 114
 115   /* quantize */
 116   return sample >> (MAD_F_FRACBITS + 1 - 16);
 117 }
 118
 119 static int decode_audio(sh_audio_t *sh,unsigned char *buf,int minlen,int maxlen){
 120   mad_decoder_t *this = (mad_decoder_t *) sh->context;
 121   int len=0;
 122
 123   while(len<minlen && len+4608<=maxlen){
 124     if(!this->have_frame) this->have_frame=read_frame(sh);
 125     if(!this->have_frame) break; // failed to sync... or EOF
 126     this->have_frame=0;
 127
 128     mad_synth_frame (&this->synth, &this->frame);
 129
 130         { unsigned int         nchannels, nsamples;
 131           mad_fixed_t const   *left_ch, *right_ch;
 132           struct mad_pcm      *pcm = &this->synth.pcm;
 133           uint16_t            *output = (uint16_t*) buf;
 134
 135           nchannels = pcm->channels;
 136           nsamples  = pcm->length;
 137           left_ch   = pcm->samples[0];
 138           right_ch  = pcm->samples[1];
 139
 140           len+=2*nchannels*nsamples;
 141           buf+=2*nchannels*nsamples;
 142
 143           while (nsamples--) {
 144             /* output sample(s) in 16-bit signed little-endian PCM */
 145
 146             *output++ = scale(*left_ch++);
 147
 148             if (nchannels == 2)
 149               *output++ = scale(*right_ch++);
 150
 151           }
 152         }
 153   }
 154
 155   return len?len:-1;
 156 }
 157
 158 static int control(sh_audio_t *sh,int cmd,void* arg, ...){
 159   mad_decoder_t *this = (mad_decoder_t *) sh->context;
 160     // various optional functions you MAY implement:
 161     switch(cmd){
 162       case ADCTRL_RESYNC_STREAM:
 163         this->have_frame=0;
 164         mad_synth_init  (&this->synth);
 165         mad_stream_init (&this->stream);
 166         mad_frame_init  (&this->frame);
 167         return CONTROL_TRUE;
 168       case ADCTRL_SKIP_FRAME:
 169         this->have_frame=read_frame(sh);
 170         return CONTROL_TRUE;
 171     }
 172   return CONTROL_UNKNOWN;
 173 }
 174 #endif