2 MS ADPCM Decoder for MPlayer
5 This file is responsible for decoding Microsoft ADPCM data.
6 Details about the data format can be found here:
7 http://www.pcisys.net/~melanson/codecs/
16 #include "ad_internal.h"
18 static ad_info_t info
=
20 "MS ADPCM audio decoder",
29 static int ms_adapt_table
[] =
31 230, 230, 230, 230, 307, 409, 512, 614,
32 768, 614, 512, 409, 307, 230, 230, 230
35 static int ms_adapt_coeff1
[] =
37 256, 512, 0, 192, 240, 460, 392
40 static int ms_adapt_coeff2
[] =
42 0, -256, 0, 64, 0, -208, -232
45 #define MS_ADPCM_PREAMBLE_SIZE 6
47 #define LE_16(x) ((x)[0]+(256*((x)[1])))
48 //#define LE_16(x) (le2me_16((x)[1]+(256*((x)[0]))))
49 //#define LE_16(x) (le2me_16(*(unsigned short *)(x)))
50 //#define LE_32(x) (le2me_32(*(unsigned int *)(x)))
53 // clamp a number between 0 and 88
54 #define CLAMP_0_TO_88(x) if (x < 0) x = 0; else if (x > 88) x = 88;
55 // clamp a number within a signed 16-bit range
56 #define CLAMP_S16(x) if (x < -32768) x = -32768; \
57 else if (x > 32767) x = 32767;
58 // clamp a number above 16
59 #define CLAMP_ABOVE_16(x) if (x < 16) x = 16;
60 // sign extend a 16-bit value
61 #define SE_16BIT(x) if (x & 0x8000) x -= 0x10000;
62 // sign extend a 4-bit value
63 #define SE_4BIT(x) if (x & 0x8) x -= 0x10;
65 static int preinit(sh_audio_t
*sh_audio
)
67 sh_audio
->audio_out_minsize
= sh_audio
->wf
->nBlockAlign
* 4;
68 sh_audio
->ds
->ss_div
=
69 (sh_audio
->wf
->nBlockAlign
- MS_ADPCM_PREAMBLE_SIZE
) * 2;
70 sh_audio
->audio_in_minsize
=
71 sh_audio
->ds
->ss_mul
= sh_audio
->wf
->nBlockAlign
;
75 static int init(sh_audio_t
*sh_audio
)
77 sh_audio
->channels
=sh_audio
->wf
->nChannels
;
78 sh_audio
->samplerate
=sh_audio
->wf
->nSamplesPerSec
;
79 sh_audio
->i_bps
= sh_audio
->wf
->nBlockAlign
*
80 (sh_audio
->channels
*sh_audio
->samplerate
) / sh_audio
->ds
->ss_div
;
81 sh_audio
->samplesize
=2;
86 static void uninit(sh_audio_t
*sh_audio
)
90 static int control(sh_audio_t
*sh_audio
,int cmd
,void* arg
, ...)
92 if(cmd
==ADCTRL_SKIP_FRAME
){
93 demux_read_data(sh_audio
->ds
, sh_audio
->a_in_buffer
,sh_audio
->ds
->ss_mul
);
96 return CONTROL_UNKNOWN
;
99 static int ms_adpcm_decode_block(unsigned short *output
, unsigned char *input
,
100 int channels
, int block_size
)
102 int current_channel
= 0;
110 int upper_nibble
= 1;
112 int snibble
; // signed nibble
115 // fetch the header information, in stereo if both channels are present
116 if (input
[stream_ptr
] > 6)
117 mp_msg(MSGT_DECAUDIO
, MSGL_WARN
,
118 "MS ADPCM: coefficient (%d) out of range (should be [0..6])\n",
120 coeff1
[0] = ms_adapt_coeff1
[input
[stream_ptr
]];
121 coeff2
[0] = ms_adapt_coeff2
[input
[stream_ptr
]];
125 if (input
[stream_ptr
] > 6)
126 mp_msg(MSGT_DECAUDIO
, MSGL_WARN
,
127 "MS ADPCM: coefficient (%d) out of range (should be [0..6])\n",
129 coeff1
[1] = ms_adapt_coeff1
[input
[stream_ptr
]];
130 coeff2
[1] = ms_adapt_coeff2
[input
[stream_ptr
]];
134 idelta
[0] = LE_16(&input
[stream_ptr
]);
139 idelta
[1] = LE_16(&input
[stream_ptr
]);
144 sample1
[0] = LE_16(&input
[stream_ptr
]);
146 SE_16BIT(sample1
[0]);
149 sample1
[1] = LE_16(&input
[stream_ptr
]);
151 SE_16BIT(sample1
[1]);
154 sample2
[0] = LE_16(&input
[stream_ptr
]);
156 SE_16BIT(sample2
[0]);
159 sample2
[1] = LE_16(&input
[stream_ptr
]);
161 SE_16BIT(sample2
[1]);
166 output
[out_ptr
++] = sample2
[0];
167 output
[out_ptr
++] = sample1
[0];
169 output
[out_ptr
++] = sample2
[0];
170 output
[out_ptr
++] = sample2
[1];
171 output
[out_ptr
++] = sample1
[0];
172 output
[out_ptr
++] = sample1
[1];
175 while (stream_ptr
< block_size
)
177 // get the next nibble
179 nibble
= snibble
= input
[stream_ptr
] >> 4;
181 nibble
= snibble
= input
[stream_ptr
++] & 0x0F;
186 ((sample1
[current_channel
] * coeff1
[current_channel
]) +
187 (sample2
[current_channel
] * coeff2
[current_channel
])) / 256) +
188 (snibble
* idelta
[current_channel
]);
189 CLAMP_S16(predictor
);
190 sample2
[current_channel
] = sample1
[current_channel
];
191 sample1
[current_channel
] = predictor
;
192 output
[out_ptr
++] = predictor
;
194 // compute the next adaptive scale factor (a.k.a. the variable idelta)
195 idelta
[current_channel
] =
196 (ms_adapt_table
[nibble
] * idelta
[current_channel
]) / 256;
197 CLAMP_ABOVE_16(idelta
[current_channel
]);
199 // toggle the channel
200 current_channel
^= channels
- 1;
203 return (block_size
- (MS_ADPCM_PREAMBLE_SIZE
* channels
)) * 2;
206 static int decode_audio(sh_audio_t
*sh_audio
,unsigned char *buf
,int minlen
,int maxlen
)
208 if (demux_read_data(sh_audio
->ds
, sh_audio
->a_in_buffer
,
209 sh_audio
->ds
->ss_mul
) !=
210 sh_audio
->ds
->ss_mul
)
213 return 2 * ms_adpcm_decode_block(
214 (unsigned short*)buf
, sh_audio
->a_in_buffer
,
215 sh_audio
->wf
->nChannels
, sh_audio
->wf
->nBlockAlign
);