近期一直不間斷學習音頻處理，一直也沒想着要去碰音頻編解碼相關。
主要是覺得沒什么實際的作用和意義。
不管視頻編解碼，圖像編解碼，音頻編解碼，都有很多組織基金在推動。
當然，在一些特定的情景下，需要用起來編解碼庫，
而一般這些庫都會有編譯困難，使用困難等等困難綜合症。
圖像方面，已經有stb_image,spot,freeimage等編解碼庫系列，做得特別贊。
https://github.com/nothings/stb/
https://github.com/r-lyeh-archived/spot
http://freeimage.sourceforge.net/index.html
當然有一段時間，jpeg的編碼庫也是個頭疼的事情，直到tinyjpg的出現。
視頻這塊有libav,ffmpeg
而音頻這塊，就有點差強人意了。
當然dr_libs 也已經做了不少工作了。
https://github.com/mackron/dr_libs
可惜的是，他做了wav的編解碼庫，mp3的解碼庫，就是沒有mp3的編碼庫。
而一般mp3 的編碼庫，大眾使用最多的是lame
在一陣尋尋覓覓之后，俺找到了一個mp3的編碼庫。
其原官網已經成為歷史資源了。
https://web.archive.org/web/20060102002813/http://www.everett9981.freeserve.co.uk/pete.htm
也是相當歷史久遠了。
也有人對其進行了回爐重造。
https://github.com/toots/shine
俺一直惦念着，找個時間，進行代碼整合，blabla
秉承着簡潔簡單的態度，就這么新鮮出爐了。
在寫示例代碼的時候，踩了幾個小坑。
貼上完整代碼:
1 #include <stdio.h> 2 #include <stdlib.h> 3 #include <string.h> 4 #include <time.h> 5 #include "timing.h" 6 #include "shine_mp3.h" 7 8 #define DR_WAV_IMPLEMENTATION 9 10 #include "dr_wav.h" 11 12 #define DR_MP3_IMPLEMENTATION 13 14 #include "dr_mp3.h" 15 16 void error(char *s); 17 18 19 int16_t *wavRead_int16(char *filename, uint32_t *sampleRate, uint32_t *channels, uint64_t *totalSampleCount) { 20 int16_t *buffer = drwav_open_and_read_file_s16(filename, channels, sampleRate, totalSampleCount); 21 if (buffer == NULL) { 22 drmp3_config pConfig; 23 float *mp3_buffer = drmp3_open_and_decode_file_f32(filename, &pConfig, totalSampleCount); 24 if (mp3_buffer != NULL) { 25 buffer = (int16_t *) calloc(*totalSampleCount, sizeof(int16_t)); 26 *channels = pConfig.outputChannels; 27 *sampleRate = pConfig.outputSampleRate; 28 if (buffer != NULL) 29 drwav_f32_to_s16(buffer, mp3_buffer, *totalSampleCount); 30 free(mp3_buffer); 31 } else { 32 printf("read file [%s] error.\n", filename); 33 } 34 } 35 return buffer; 36 } 37 38 39 /* Some global vars. */ 40 char *infname, *outfname; 41 FILE *outfile; 42 int quiet = 0; 43 int stereo = STEREO; 44 int force_mono = 0; 45 46 /* Write out the MP3 file */ 47 int write_mp3(long bytes, void *buffer, void *config) { 48 return fwrite(buffer, sizeof(unsigned char), bytes, outfile) / sizeof(unsigned char); 49 } 50 51 /* Output error message and exit */ 52 void error(char *s) { 53 fprintf(stderr, "Error: %s\n", s); 54 exit(1); 55 } 56 57 static void print_usage() { 58 printf("Audio Processing\n"); 59 printf("mp3 encoder && decoder\n"); 60 printf("blog: http://cpuimage.cnblogs.com/\n"); 61 printf("Usage: mp3 encoder && decoder [options] <infile> <outfile>\n\n"); 62 printf("Use \"-\" for standard input or output.\n\n"); 63 printf("Options:\n"); 64 printf(" -h this help message\n"); 65 printf(" -b <bitrate> set the bitrate [8-320], default 64 kbit\n"); 66 printf(" -m force encoder to operate in mono\n"); 67 printf(" -c set copyright flag, default off\n"); 68 printf(" -j encode in joint stereo (stereo data only)\n"); 69 printf(" -d encode in dual-channel (stereo data only)\n"); 70 printf(" -q quiet mode\n"); 71 printf(" -v verbose mode\n"); 72 } 73 74 /* Use these default settings, can be overridden */ 75 static void set_defaults(shine_config_t *config) { 76 shine_set_config_mpeg_defaults(&config->mpeg); 77 } 78 79 /* Parse command line arguments */ 80 static int parse_command(int argc, char **argv, shine_config_t *config) { 81 int i = 0; 82 83 if (argc < 3) return 0; 84 85 while (argv[++i][0] == '-' && argv[i][1] != '\000' && argv[i][1] != ' ') 86 switch (argv[i][1]) { 87 case 'b': 88 config->mpeg.bitr = atoi(argv[++i]); 89 break; 90 91 case 'm': 92 force_mono = 1; 93 break; 94 95 case 'j': 96 stereo = JOINT_STEREO; 97 break; 98 99 case 'd': 100 stereo = DUAL_CHANNEL; 101 break; 102 103 case 'c': 104 config->mpeg.copyright = 1; 105 break; 106 107 case 'q': 108 quiet = 1; 109 break; 110 111 case 'v': 112 quiet = 0; 113 break; 114 115 case 'h': 116 default : 117 return 0; 118 } 119 120 if (argc - i != 2) return 0; 121 infname = argv[i++]; 122 outfname = argv[i]; 123 return 1; 124 } 125 126 /* Print some info about what we're going to encode */ 127 static void check_config(shine_config_t *config) { 128 static char *version_names[4] = {"2.5", "reserved", "II", "I"}; 129 static char *mode_names[4] = {"stereo", "joint-stereo", "dual-channel", "mono"}; 130 static char *demp_names[4] = {"none", "50/15us", "", "CITT"}; 131 132 printf("MPEG-%s layer III, %s Psychoacoustic Model: Shine\n", 133 version_names[shine_check_config(config->wave.samplerate, config->mpeg.bitr)], 134 mode_names[config->mpeg.mode]); 135 printf("Bitrate: %d kbps ", config->mpeg.bitr); 136 printf("De-emphasis: %s %s %s\n", 137 demp_names[config->mpeg.emph], 138 ((config->mpeg.original) ? "Original" : ""), 139 ((config->mpeg.copyright) ? "(C)" : "")); 140 printf("Encoding \"%s\" to \"%s\"\n", infname, outfname); 141 } 142 143 int main(int argc, char **argv) { 144 shine_config_t config; 145 shine_t s; 146 int written; 147 unsigned char *data; 148 /* Set the default MPEG encoding paramters - basically init the struct */ 149 set_defaults(&config); 150 151 if (!parse_command(argc, argv, &config)) { 152 print_usage(); 153 exit(1); 154 } 155 156 quiet = quiet || !strcmp(outfname, "-"); 157 158 if (!quiet) { 159 printf("Audio Processing\n"); 160 printf("mp3 encoder && decoder\n"); 161 printf("blog:http://cpuimage.cnblogs.com/\n"); 162 } 163 uint32_t sampleRate = 0; 164 uint64_t totalSampleCount = 0; 165 uint32_t channels = 0; 166 int16_t *data_in = wavRead_int16(infname, &sampleRate, &channels, &totalSampleCount); 167 if (data_in == NULL) 168 return -1; 169 double startTime = now(); 170 config.wave.samplerate = sampleRate; 171 config.wave.channels = channels; 172 173 if (force_mono) 174 config.wave.channels = 1; 175 176 /* See if samplerate and bitrate are valid */ 177 if (shine_check_config(config.wave.samplerate, config.mpeg.bitr) < 0) 178 error("Unsupported samplerate/bitrate configuration."); 179 180 /* open the output file */ 181 if (!strcmp(outfname, "-")) 182 outfile = stdout; 183 else 184 outfile = fopen(outfname, "wb"); 185 if (!outfile) { 186 fprintf(stderr, "Could not create \"%s\".\n", outfname); 187 exit(1); 188 } 189 190 /* Set to stereo mode if wave data is stereo, mono otherwise. */ 191 if (config.wave.channels > 1) 192 config.mpeg.mode = stereo; 193 else 194 config.mpeg.mode = MONO; 195 196 /* Initiate encoder */ 197 s = shine_initialise(&config); 198 199 // assert(s != NULL); 200 /* Print some info about the file about to be created (optional) */ 201 if (!quiet) check_config(&config); 202 203 int samples_per_pass = shine_samples_per_pass(s) * channels; 204 205 /* All the magic happens here */ 206 size_t count = totalSampleCount / samples_per_pass; 207 int16_t *buffer = data_in; 208 for (int i = 0; i < count; i++) { 209 data = shine_encode_buffer_interleaved(s, buffer, &written); 210 if (write_mp3(written, data, &config) != written) { 211 fprintf(stderr, "mp3 encoder && decoder: write error\n"); 212 return 1; 213 } 214 buffer += samples_per_pass; 215 } 216 size_t last = totalSampleCount % samples_per_pass; 217 if (last != 0) { 218 int16_t *cache = (int16_t *) calloc(samples_per_pass, sizeof(int16_t)); 219 if (cache != NULL) { 220 memcpy(cache, buffer, last * sizeof(int16_t)); 221 data = shine_encode_buffer_interleaved(s, cache, &written); 222 free(cache); 223 if (write_mp3(written, data, &config) != written) { 224 fprintf(stderr, "mp3 encoder && decoder: write error\n"); 225 return 1; 226 } 227 } 228 } 229 /* Flush and write remaining data. */ 230 data = shine_flush(s, &written); 231 write_mp3(written, data, &config); 232 /* Close encoder. */ 233 shine_close(s); 234 /* Close the MP3 file */ 235 fclose(outfile); 236 free(data_in); 237 double time_interval = calcElapsed(startTime, now()); 238 if (!quiet) 239 printf("time interval: %d ms\n ", (int) (time_interval * 1000)); 240 241 return 0; 242 }
熟悉我的風格的朋友們，估計一看就清楚了。
也不多做解釋，當然了，這份代碼是學習mp3編解碼的不二之選。
使用示例:
tinymp3 -b 64 input.mp3 ouput.mp3
tinymp3 -b 64 input.wav ouput.mp3
相關參數說明：
Usage: tinymp3 [options] <infile> <outfile>
Use "-" for standard input or output.
Options:
-h this help message
-b <bitrate> set the bitrate [8-320], default 64 kbit
-m force encoder to operate in mono
-c set copyright flag, default off
-j encode in joint stereo (stereo data only)
-d encode in dual-channel (stereo data only)
-q quiet mode
不做解釋，直接上取下項目，cmake一下，你懂的。
項目地址:
https://github.com/cpuimage/tinymp3
前面有不少朋友問到音頻重采樣庫的問題，抽空整理了下speex的resampler。
我想重采樣這方面也是夠用的了。
項目地址:
https://github.com/cpuimage/speex_resampler
以上，權當拋磚引玉。
另外感謝 熱心網友打賞兩瓶可樂。
獨樂樂，不如眾樂樂。
若有其他相關問題或者需求也可以郵件聯系俺探討。
郵箱地址是:
gaozhihan@vip.qq.com