mdw@git.distorted.org.uk Git - disorder/blob - lib/resample.c

   1 /*
   2  * This file is part of DisOrder.
   3  * Copyright (C) 2009 Richard Kettlewell
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 /** @file lib/resample.c
  20  * @brief Audio resampling
  21  *
  22  * General purpose audio format conversion.  Rate conversion only works if the
  23  * SRC samplerate library is available, but the bitness/channel/endianness
  24  * conversion works regardless.
  25  */
  26
  27 #include "common.h"
  28 #include "resample.h"
  29 #include "log.h"
  30 #include "mem.h"
  31
  32 /** @brief Number of intermediate-format samples */
  33 #define SAMPLES 1024
  34
  35 /** @brief Multiplier for signed formats to allow easy switching */
  36 #define SIGNED 4
  37
  38 /** @brief Initialize a resampler
  39  * @param rs Resampler
  40  * @param input_bits Bits/sample in input
  41  * @param input_channels Number of input channels
  42  * @param input_signed Whether input samples are signed or unsigned
  43  * @param input_rate Frames/second in input
  44  * @param output_bits Bits/sample in output
  45  * @param output_channels Number of output channels
  46  * @param output_rate Frames/second in output
  47  * @param output_signed Whether output samples are signed or unsigned
  48  *
  49  * For formats with more than two channels it's assume that the first
  50  * two channels are left and right.  No particular meaning is attached
  51  * to additional channels other than to assume channel N in an input
  52  * means the same as channel N in an output, for N>1.
  53  */
  54 void resample_init(struct resampler *rs,
  55                     int input_bits, int input_channels,
  56                     int input_rate, int input_signed,
  57                     int input_endian,
  58                     int output_bits, int output_channels,
  59                     int output_rate, int output_signed,
  60                     int output_endian) {
  61   int error_;
  62   memset(rs, 0, sizeof *rs);
  63   assert(input_bits == 8 || input_bits == 16);
  64   assert(output_bits == 8 || output_bits == 16);
  65   assert(input_endian == ENDIAN_BIG || input_endian == ENDIAN_LITTLE);
  66   assert(output_endian == ENDIAN_BIG || output_endian == ENDIAN_LITTLE);
  67   assert(ENDIAN_BIG >= 0 && ENDIAN_BIG < SIGNED);
  68   assert(ENDIAN_LITTLE >= 0 && ENDIAN_LITTLE < SIGNED);
  69   rs->input_bits = input_bits;
  70   rs->input_channels = input_channels;
  71   rs->input_rate = input_rate;
  72   rs->input_signed = SIGNED * !!input_signed;
  73   rs->input_endian = input_endian;
  74   rs->output_bits = output_bits;
  75   rs->output_channels = output_channels;
  76   rs->output_rate = output_rate;
  77   rs->output_signed = SIGNED * !!output_signed;
  78   rs->output_endian = output_endian;
  79   rs->input_bytes_per_sample = (rs->input_bits + 7) / 8;
  80   rs->input_bytes_per_frame = rs->input_channels * rs->input_bytes_per_sample;
  81   if(rs->input_rate != rs->output_rate) {
  82 #if HAVE_SAMPLERATE_H
  83     rs->state = src_new(SRC_SINC_BEST_QUALITY, rs->output_channels, &error_);
  84     if(!rs->state)
  85       fatal(0, "calling src_new: %s", src_strerror(error_));
  86 #else
  87     fatal(0, "need to resample audio data but libsamplerate not available");
  88 #endif
  89   }
  90 }
  91
  92 /** @brief Destroy a resampler
  93  * @param rs Resampler
  94  */
  95 void resample_close(struct resampler *rs) {
  96 #if HAVE_SAMPLERATE_H
  97   if(rs->state)
  98     src_delete(rs->state);
  99 #endif
 100 }
 101
 102 /** @brief Get one sample value and normalize it to [-1,1]
 103  * @param rs Resampler state
 104  * @param bytes Pointer to input data
 105  * @param where Where to store result
 106  * @return Number of bytes consumed
 107  */
 108 static size_t resample_get_sample(struct resampler *rs,
 109                                   const uint8_t *bytes,
 110                                   float *where) {
 111   switch(rs->input_bits + rs->input_signed + rs->input_endian) {
 112   case 8+ENDIAN_BIG:
 113   case 8+ENDIAN_LITTLE:
 114     *where = (bytes[0] - 128)/ 128;
 115     return 1;
 116   case 8+SIGNED+ENDIAN_BIG:
 117   case 8+SIGNED+ENDIAN_LITTLE:
 118     *where = (int8_t)bytes[0] / 128;
 119     return 1;
 120   case 16+ENDIAN_BIG:
 121     *where = (bytes[0] * 256 + bytes[1] - 32768)/ 32768.0;
 122     return 2;
 123     break;
 124   case 16+ENDIAN_LITTLE:
 125     *where = (bytes[1] * 256 + bytes[0] - 32768)/ 32768.0;
 126     return 2;
 127     break;
 128   case 16+SIGNED+ENDIAN_BIG:
 129     *where = (int16_t)(bytes[0] * 256 + bytes[1])/ 32768.0;
 130     return 2;
 131     break;
 132   case 16+SIGNED+ENDIAN_LITTLE:
 133     *where = (int16_t)(bytes[1] * 256 + bytes[0])/ 32768.0;
 134     return 2;
 135     break;
 136   default:
 137     assert(!"unsupported sample format");
 138   }
 139 }
 140
 141 static inline int clip(int n, int min, int max) {
 142   if(n >= min) {
 143     if(n <= max)
 144       return n;
 145     else
 146       return max;
 147   } else
 148     return min;
 149 }
 150
 151 /** @brief Store one sample value
 152  * @param rs Resampler state
 153  * @param sample Sample value
 154  * @param bytes Where to store it
 155  * @return Number of bytes stored
 156  *
 157  * The value is clipped naively if it will not fit.
 158  */
 159 static size_t resample_put_sample(struct resampler *rs,
 160                                   float sample,
 161                                   uint8_t *bytes) {
 162   unsigned value;
 163   switch(rs->input_bits + rs->input_signed + rs->input_endian) {
 164   case 8+ENDIAN_BIG:
 165   case 8+ENDIAN_LITTLE:
 166     *bytes = clip(sample * 128.0 + 128, 0, 255);
 167     return 1;
 168   case 8+SIGNED+ENDIAN_BIG:
 169   case 8+SIGNED+ENDIAN_LITTLE:
 170     *bytes = clip((int)(sample * 128.0), -128, 127);
 171     return 1;
 172   case 16+ENDIAN_BIG:                   /* unsigned */
 173     value = clip(sample * 32768.0 + 32768, 0, 65535);
 174     *bytes++ = value >> 8;
 175     *bytes++ = value;
 176     return 2;
 177   case 16+ENDIAN_LITTLE:
 178     value = clip(sample * 32768.0 + 32768, 0, 65535);
 179     *bytes++ = value;
 180     *bytes++ = value >> 8;
 181     return 2;
 182   case 16+SIGNED+ENDIAN_BIG:
 183     value = clip(sample * 32768.0, -32768, 32767);
 184     *bytes++ = value >> 8;
 185     *bytes++ = value;
 186     return 2;
 187   case 16+SIGNED+ENDIAN_LITTLE:
 188     value = clip(sample * 32768.0, -32768, 32767);
 189     *bytes++ = value;
 190     *bytes++ = value >> 8;
 191     return 2;
 192   default:
 193     assert(!"unsupported sample format");
 194   }
 195 }
 196
 197 /** @brief Convert input samples to floats
 198  * @param rs Resampler state
 199  * @param bytes Input bytes
 200  * @param nbytes Number of input bytes
 201  * @param floats Where to store converted data
 202  *
 203  * @p floats must be big enough.  As well as converting to floats this
 204  * also converts to the output's channel format.
 205  *
 206  * Excess input channels are just discarded.  If there are insufficient input
 207  * channels the last one is duplicated as often as necessary to make up the
 208  * numbers.  This is a rather naff heuristic and may be improved in a future
 209  * version, but mostly in DisOrder the output is pretty much always stereo and
 210  * the input either mono or stereo, so the result isn't actually going to be
 211  * too bad.
 212  */
 213 static void resample_prepare_input(struct resampler *rs,
 214                                    const uint8_t *bytes,
 215                                    size_t nbytes,
 216                                    float *floats) {
 217   size_t nframes = nbytes / (rs->input_bytes_per_frame);
 218
 219   while(nframes > 0) {
 220     int n;
 221
 222     for(n = 0; n < rs->input_channels && n < rs->output_channels; ++n) {
 223       bytes += resample_get_sample(rs, bytes, floats);
 224       ++floats;
 225     }
 226     if(n < rs->input_channels) {
 227       /* More input channels; discard them */
 228       bytes += (rs->input_channels - n) * rs->input_bytes_per_sample;
 229     } else if(n < rs->output_channels) {
 230       /* More output channels; duplicate the last input channel */
 231       for(; n < rs->output_channels; ++n) {
 232         *floats = floats[-1];
 233         ++floats;
 234       }
 235     }
 236   }
 237 }
 238
 239 /** @brief Convert between sample formats
 240  * @param rs Resampler state
 241  * @param bytes Bytes to convert
 242  * @param nbytes Number of bytes to convert
 243  * @param eof Set an end of input stream
 244  * @param converted Called with converted data (possibly more than once)
 245  * @return Number of bytes consumed
 246  */
 247 size_t resample_convert(struct resampler *rs,
 248                         const uint8_t *bytes,
 249                         size_t nbytes,
 250                         int eof,
 251                         void (*converted)(uint8_t *bytes,
 252                                           size_t nbytes)) {
 253   size_t nframesin = nbytes / (rs->input_bytes_per_frame);
 254   size_t nsamplesout;
 255   float *input = xcalloc(nframesin * rs->output_channels, sizeof (float));
 256   float *output = 0;
 257
 258   resample_prepare_input(rs, bytes, nbytes, input);
 259 #if HAVE_SAMPLERATE_H
 260   if(rs->state) {
 261     /* A sample-rate conversion must be performed */
 262     SRC_DATA data;
 263     /* Compute how many frames are expected to come out. */
 264     size_t maxframesout = nframesin * rs->output_rate / rs->input_rate + 1;
 265     output = xcalloc(maxframesout * rs->output_channels, sizeof(float));
 266     data.data_in = input;
 267     data.data_out = output;
 268     data.input_frames = nframesin;
 269     data.output_frames = maxframesout;
 270     data.end_of_input = eof;
 271     data.src_ratio = rs->output_rate / rs->input_rate;
 272     int error_ = src_process(rs->state, &data);
 273     if(error_)
 274       fatal(0, "calling src_process: %s", src_strerror(error_));
 275     nframesin = data.input_frames_used;
 276     nsamplesout = data.output_frames_gen * rs->output_channels;
 277   }
 278 #endif
 279   if(!output) {
 280     /* No sample-rate conversion required */
 281     output = input;
 282     nsamplesout = nframesin * rs->output_channels;
 283   }
 284   const float *op = output;
 285   while(nsamplesout > 0) {
 286     uint8_t buffer[4096];
 287     size_t bufused = 0;
 288
 289     while(bufused < sizeof buffer && nsamplesout > 0) {
 290       bufused += resample_put_sample(rs, *op++, buffer + bufused);
 291       --nsamplesout;
 292     }
 293     converted(buffer, bufused);
 294   }
 295   if(output != input)
 296     xfree(output);
 297   xfree(input);
 298   /* Report how many input bytes were actually consumed */
 299   return nframesin * rs->input_bytes_per_frame;
 300 }
 301
 302 /*
 303 Local Variables:
 304 c-basic-offset:2
 305 comment-column:40
 306 fill-column:79
 307 indent-tabs-mode:nil
 308 End:
 309 */