libmpcodecs/ad_sample.c

   1 // SAMPLE audio decoder - you can use this file as template when creating new codec!
   2
   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 <unistd.h>
  24
  25 #include "config.h"
  26 #include "ad_internal.h"
  27
  28 static const ad_info_t info = {
  29         "Sample audio decoder",  // name of the driver
  30         "sample",    // driver name. should be the same as filename without ad_
  31         "A'rpi",     // writer/maintainer of _this_ file
  32         "",          // writer/maintainer/site of the _codec_
  33         ""           // comments
  34 };
  35
  36 LIBAD_EXTERN(sample)
  37
  38 #include "libsample/sample.h" // include your codec's .h files here
  39
  40 static int preinit(sh_audio_t *sh){
  41   // let's check if the driver is available, return 0 if not.
  42   // (you should do that if you use external lib(s) which is optional)
  43   ...
  44
  45   // there are default values set for buffering, but you can override them:
  46
  47   // minimum output buffer size (should be the uncompressed max. frame size)
  48   sh->audio_out_minsize=4*2*1024; // in this sample, we assume max 4 channels,
  49                                   // 2 bytes/sample and 1024 samples/frame
  50                                   // Default: 8192
  51
  52   // minimum input buffer size (set only if you need input buffering)
  53   // (should be the max compressed frame size)
  54   sh->audio_in_minsize=2048; // Default: 0 (no input buffer)
  55
  56   // if you set audio_in_minsize non-zero, the buffer will be allocated
  57   // before the init() call by the core, and you can access it via
  58   // pointer: sh->audio_in_buffer
  59   // it will free'd after uninit(), so you don't have to use malloc/free here!
  60
  61   // the next few parameters define the audio format (channels, sample type,
  62   // in/out bitrate etc.). it's OK to move these to init() if you can set
  63   // them only after some initialization:
  64
  65   sh->samplesize=2;              // bytes (not bits!) per sample per channel
  66   sh->channels=2;                // number of channels
  67   sh->samplerate=44100;          // samplerate
  68   sh->sample_format=AF_FORMAT_S16_LE; // sample format, see libao2/afmt.h
  69
  70   sh->i_bps=64000/8; // input data rate (compressed bytes per second)
  71   // Note: if you have VBR or unknown input rate, set it to some common or
  72   // average value, instead of zero. it's used to predict time delay of
  73   // buffered compressed bytes, so it must be more-or-less real!
  74
  75 //sh->o_bps=...     // output data rate (uncompressed bytes per second)
  76   // Note: you DON'T need to set o_bps in most cases, as it defaults to:
  77   //   sh->samplesize*sh->channels*sh->samplerate;
  78
  79   // for constant rate compressed QuickTime (.mov files) codecs you MUST
  80   // set the compressed and uncompressed packet size (used by the demuxer):
  81   sh->ds->ss_mul = 34; // compressed packet size
  82   sh->ds->ss_div = 64; // samples per packet
  83
  84   return 1; // return values: 1=OK 0=ERROR
  85 }
  86
  87 static int init(sh_audio_t *sh_audio){
  88   // initialize the decoder, set tables etc...
  89
  90   // you can store HANDLE or private struct pointer at sh->context
  91   // you can access WAVEFORMATEX header at sh->wf
  92
  93   // set sample format/rate parameters if you didn't do it in preinit() yet.
  94
  95   return 1; // return values: 1=OK 0=ERROR
  96 }
  97
  98 static void uninit(sh_audio_t *sh){
  99   // uninit the decoder etc...
 100   // again: you don't have to free() a_in_buffer here! it's done by the core.
 101 }
 102
 103 static int decode_audio(sh_audio_t *sh_audio,unsigned char *buf,int minlen,int maxlen){
 104
 105   // audio decoding. the most important thing :)
 106   // parameters you get:
 107   //  buf = pointer to the output buffer, you have to store uncompressed
 108   //        samples there
 109   //  minlen = requested minimum size (in bytes!) of output. it's just a
 110   //        _recommendation_, you can decode more or less, it just tell you that
 111   //        the caller process needs 'minlen' bytes. if it gets less, it will
 112   //        call decode_audio() again.
 113   //  maxlen = maximum size (bytes) of output. you MUST NOT write more to the
 114   //        buffer, it's the upper-most limit!
 115   //        note: maxlen will be always greater or equal to sh->audio_out_minsize
 116
 117   // now, let's decode...
 118
 119   // you can read the compressed stream using the demux stream functions:
 120   //  demux_read_data(sh->ds, buffer, length) - read 'length' bytes to 'buffer'
 121   //  ds_get_packet(sh->ds, &buffer) - set ptr buffer to next data packet
 122   // (both func return number of bytes or 0 for error)
 123
 124   return len; // return value: number of _bytes_ written to output buffer,
 125               // or -1 for EOF (or uncorrectable error)
 126 }
 127
 128 static int control(sh_audio_t *sh,int cmd,void* arg, ...){
 129     // various optional functions you MAY implement:
 130     switch(cmd){
 131       case ADCTRL_RESYNC_STREAM:
 132         // it is called once after seeking, to resync.
 133         // Note: sh_audio->a_in_buffer_len=0; is done _before_ this call!
 134         ...
 135         return CONTROL_TRUE;
 136       case ADCTRL_SKIP_FRAME:
 137         // it is called to skip (jump over) small amount (1/10 sec or 1 frame)
 138         // of audio data - used to sync audio to video after seeking
 139         // if you don't return CONTROL_TRUE, it will defaults to:
 140         //      ds_fill_buffer(sh_audio->ds);  // skip 1 demux packet
 141         ...
 142         return CONTROL_TRUE;
 143     }
 144   return CONTROL_UNKNOWN;
 145 }