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// SAMPLE audio decoder - you can use this file as template when creating new codec!
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "config.h"
#include "ad_internal.h"
static const ad_info_t info = {
"libmad mpeg audio decoder",
"libmad",
"A'rpi",
"libmad...",
"based on Xine's libmad/xine_decoder.c"
};
LIBAD_EXTERN(libmad)
#include <mad.h>
typedef struct mad_decoder_s {
struct mad_synth synth;
struct mad_stream stream;
struct mad_frame frame;
int have_frame;
int output_sampling_rate;
int output_open;
int output_mode;
} mad_decoder_t;
static int preinit(sh_audio_t *sh){
mad_decoder_t *this = (mad_decoder_t *) malloc(sizeof(mad_decoder_t));
memset(this,0,sizeof(mad_decoder_t));
sh->context = this;
mad_synth_init (&this->synth);
mad_stream_init (&this->stream);
mad_frame_init (&this->frame);
sh->audio_out_minsize=2*4608;
sh->audio_in_minsize=4096;
return 1;
}
static int read_frame(sh_audio_t *sh){
mad_decoder_t *this = (mad_decoder_t *) sh->context;
int len;
while((len=demux_read_data(sh->ds,&sh->a_in_buffer[sh->a_in_buffer_len],
sh->a_in_buffer_size-sh->a_in_buffer_len))>0){
sh->a_in_buffer_len+=len;
while(1){
int ret;
mad_stream_buffer (&this->stream, sh->a_in_buffer, sh->a_in_buffer_len);
ret=mad_frame_decode (&this->frame, &this->stream);
if (this->stream.next_frame) {
int num_bytes =
(char*)sh->a_in_buffer+sh->a_in_buffer_len - (char*)this->stream.next_frame;
memmove(sh->a_in_buffer, this->stream.next_frame, num_bytes);
mp_msg(MSGT_DECAUDIO,MSGL_DBG2,"libmad: %d bytes processed\n",sh->a_in_buffer_len-num_bytes);
sh->a_in_buffer_len = num_bytes;
}
if (ret == 0) return 1; // OK!!!
// error! try to resync!
if(this->stream.error==MAD_ERROR_BUFLEN) break;
}
}
mp_msg(MSGT_DECAUDIO,MSGL_INFO,"Cannot sync MAD frame\n");
return 0;
}
static int init(sh_audio_t *sh){
mad_decoder_t *this = (mad_decoder_t *) sh->context;
this->have_frame=read_frame(sh);
if(!this->have_frame) return 0; // failed to sync...
sh->channels=(this->frame.header.mode == MAD_MODE_SINGLE_CHANNEL) ? 1 : 2;
sh->samplerate=this->frame.header.samplerate;
sh->i_bps=this->frame.header.bitrate/8;
sh->samplesize=2;
return 1;
}
static void uninit(sh_audio_t *sh){
mad_decoder_t *this = (mad_decoder_t *) sh->context;
mad_synth_finish (&this->synth);
mad_frame_finish (&this->frame);
mad_stream_finish(&this->stream);
free(sh->context);
}
/* utility to scale and round samples to 16 bits */
static inline signed int scale(mad_fixed_t sample) {
/* round */
sample += (1L << (MAD_F_FRACBITS - 16));
/* clip */
if (sample >= MAD_F_ONE)
sample = MAD_F_ONE - 1;
else if (sample < -MAD_F_ONE)
sample = -MAD_F_ONE;
/* quantize */
return sample >> (MAD_F_FRACBITS + 1 - 16);
}
static int decode_audio(sh_audio_t *sh,unsigned char *buf,int minlen,int maxlen){
mad_decoder_t *this = (mad_decoder_t *) sh->context;
int len=0;
while(len<minlen && len+4608<=maxlen){
if(!this->have_frame) this->have_frame=read_frame(sh);
if(!this->have_frame) break; // failed to sync... or EOF
this->have_frame=0;
mad_synth_frame (&this->synth, &this->frame);
{ unsigned int nchannels, nsamples;
mad_fixed_t const *left_ch, *right_ch;
struct mad_pcm *pcm = &this->synth.pcm;
uint16_t *output = (uint16_t*) buf;
nchannels = pcm->channels;
nsamples = pcm->length;
left_ch = pcm->samples[0];
right_ch = pcm->samples[1];
len+=2*nchannels*nsamples;
buf+=2*nchannels*nsamples;
while (nsamples--) {
/* output sample(s) in 16-bit signed little-endian PCM */
*output++ = scale(*left_ch++);
if (nchannels == 2)
*output++ = scale(*right_ch++);
}
}
}
return len?len:-1;
}
static int control(sh_audio_t *sh,int cmd,void* arg, ...){
mad_decoder_t *this = (mad_decoder_t *) sh->context;
// various optional functions you MAY implement:
switch(cmd){
case ADCTRL_RESYNC_STREAM:
this->have_frame=0;
mad_synth_init (&this->synth);
mad_stream_init (&this->stream);
mad_frame_init (&this->frame);
return CONTROL_TRUE;
case ADCTRL_SKIP_FRAME:
this->have_frame=read_frame(sh);
return CONTROL_TRUE;
}
return CONTROL_UNKNOWN;
}
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