MP3 编码解码 附完整c代码

近期一直不间断学习音频处理，一直也没想着要去碰音频编解码相关。

主要是觉得没什么实际的作用和意义。

不管视频编解码，图像编解码，音频编解码，都有很多组织基金在推动。

当然，在一些特定的情景下，需要用起来编解码库，

而一般这些库都会有编译困难，使用困难等等困难综合症。

图像方面，已经有stb_image,spot,freeimage等编解码库系列，做得特别赞。

https://github.com/nothings/stb/

https://github.com/r-lyeh-archived/spot

http://freeimage.sourceforge.net/index.html

当然有一段时间，jpeg的编码库也是个头疼的事情，直到tinyjpg的出现。

视频这块有libav,ffmpeg

https://libav.org/

https://ffmpeg.org/

而音频这块，就有点差强人意了。

当然dr_libs 也已经做了不少工作了。

https://github.com/mackron/dr_libs

可惜的是，他做了wav的编解码库，mp3的解码库，就是没有mp3的编码库。

而一般mp3 的编码库，大众使用最多的是lame

http://lame.sourceforge.net/

在一阵寻寻觅觅之后，俺找到了一个mp3的编码库。

其原官网已经成为历史资源了。

https://web.archive.org/web/20060102002813/http://www.everett9981.freeserve.co.uk/pete.htm

也是相当历史久远了。

也有人对其进行了回炉重造。

https://github.com/toots/shine

俺一直惦念着，找个时间，进行代码整合，blabla

秉承着简洁简单的态度，就这么新鲜出炉了。

在写示例代码的时候，踩了几个小坑。

贴上完整代码:

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
 #include "timing.h"
 #include "shine_mp3.h"

 #define DR_WAV_IMPLEMENTATION

 #include "dr_wav.h"

 #define DR_MP3_IMPLEMENTATION

 #include "dr_mp3.h"

 void error(char *s);

 int16_t *wavRead_int16(char *filename, uint32_t *sampleRate, uint32_t *channels, uint64_t *totalSampleCount) {
     int16_t *buffer = drwav_open_and_read_file_s16(filename, channels, sampleRate, totalSampleCount);
     if (buffer == NULL) {
         drmp3_config pConfig;
         float *mp3_buffer = drmp3_open_and_decode_file_f32(filename, &pConfig, totalSampleCount);
         if (mp3_buffer != NULL) {
             buffer = (int16_t *) calloc(*totalSampleCount, sizeof(int16_t));
             *channels = pConfig.outputChannels;
             *sampleRate = pConfig.outputSampleRate;
             if (buffer != NULL)
                 drwav_f32_to_s16(buffer, mp3_buffer, *totalSampleCount);
             free(mp3_buffer);
         } else {
             printf("read file [%s] error.\n", filename);
         }
     }
     return buffer;
 }

 /* Some global vars. */
 char *infname, *outfname;
 FILE *outfile;
 int quiet = ;
 int stereo = STEREO;
 int force_mono = ;

 /* Write out the MP3 file */
 int write_mp3(long bytes, void *buffer, void *config) {
     return fwrite(buffer, sizeof(unsigned char), bytes, outfile) / sizeof(unsigned char);
 }

 /* Output error message and exit */
 void error(char *s) {
     fprintf(stderr, "Error: %s\n", s);
     exit();
 }

 static void print_usage() {
     printf("Audio Processing\n");
     printf("mp3 encoder && decoder\n");
     printf("blog: http://cpuimage.cnblogs.com/\n");
     printf("Usage: mp3 encoder && decoder [options] <infile> <outfile>\n\n");
     printf("Use \"-\" for standard input or output.\n\n");
     printf("Options:\n");
     printf(" -h            this help message\n");
     printf(" -b <bitrate>  set the bitrate [8-320], default 64 kbit\n");
     printf(" -m            force encoder to operate in mono\n");
     printf(" -c            set copyright flag, default off\n");
     printf(" -j            encode in joint stereo (stereo data only)\n");
     printf(" -d            encode in dual-channel (stereo data only)\n");
     printf(" -q            quiet mode\n");
     printf(" -v            verbose mode\n");
 }

 /* Use these default settings, can be overridden */
 static void set_defaults(shine_config_t *config) {
     shine_set_config_mpeg_defaults(&config->mpeg);
 }

 /* Parse command line arguments */
 static int parse_command(int argc, char **argv, shine_config_t *config) {
     int i = ;

     if (argc < ) return ;

     while (argv[++i][] == '-' && argv[i][] != '\000' && argv[i][] != ' ')
         switch (argv[i][]) {
             case 'b':
                 config->mpeg.bitr = atoi(argv[++i]);
                 break;

             case 'm':
                 force_mono = ;
                 break;

             case 'j':
                 stereo = JOINT_STEREO;
                 break;

             case 'd':
                 stereo = DUAL_CHANNEL;
                 break;

             case 'c':
                 config->mpeg.copyright = ;
                 break;

             case 'q':
                 quiet = ;
                 break;

             case 'v':
                 quiet = ;
                 break;

             case 'h':
             default :
                 return ;
         }

     if (argc - i != ) return ;
     infname = argv[i++];
     outfname = argv[i];
     return ;
 }

 /* Print some info about what we're going to encode */
 static void check_config(shine_config_t *config) {
     static char *version_names[] = {"2.5", "reserved", "II", "I"};
     static char *mode_names[] = {"stereo", "joint-stereo", "dual-channel", "mono"};
     static char *demp_names[] = {"none", "50/15us", "", "CITT"};

     printf("MPEG-%s layer III, %s  Psychoacoustic Model: Shine\n",
            version_names[shine_check_config(config->wave.samplerate, config->mpeg.bitr)],
            mode_names[config->mpeg.mode]);
     printf("Bitrate: %d kbps  ", config->mpeg.bitr);
     printf("De-emphasis: %s   %s %s\n",
            demp_names[config->mpeg.emph],
            ((config->mpeg.original) ? "Original" : ""),
            ((config->mpeg.copyright) ? "(C)" : ""));
     printf("Encoding \"%s\" to \"%s\"\n", infname, outfname);
 }

 int main(int argc, char **argv) {
     shine_config_t config;
     shine_t s;
     int written;
     unsigned char *data;
     /* Set the default MPEG encoding paramters - basically init the struct */
     set_defaults(&config);

     if (!parse_command(argc, argv, &config)) {
         print_usage();
         exit();
     }

     quiet = quiet || !strcmp(outfname, "-");

     if (!quiet) {
         printf("Audio Processing\n");
         printf("mp3 encoder && decoder\n");
         printf("blog:http://cpuimage.cnblogs.com/\n");
     }
     uint32_t sampleRate = ;
     uint64_t totalSampleCount = ;
     uint32_t channels = ;
     int16_t *data_in = wavRead_int16(infname, &sampleRate, &channels, &totalSampleCount);
     if (data_in == NULL)
         return -;
     double startTime = now();
     config.wave.samplerate = sampleRate;
     config.wave.channels = channels;

     if (force_mono)
         config.wave.channels = ;

     /* See if samplerate and bitrate are valid */
     if (shine_check_config(config.wave.samplerate, config.mpeg.bitr) < )
         error("Unsupported samplerate/bitrate configuration.");

     /* open the output file */
     if (!strcmp(outfname, "-"))
         outfile = stdout;
     else
         outfile = fopen(outfname, "wb");
     if (!outfile) {
         fprintf(stderr, "Could not create \"%s\".\n", outfname);
         exit();
     }

     /* Set to stereo mode if wave data is stereo, mono otherwise. */
     if (config.wave.channels > )
         config.mpeg.mode = stereo;
     else
         config.mpeg.mode = MONO;

     /* Initiate encoder */
     s = shine_initialise(&config);

     // assert(s != NULL);
     /* Print some info about the file about to be created (optional) */
     if (!quiet) check_config(&config);

     int samples_per_pass = shine_samples_per_pass(s) * channels;

     /* All the magic happens here */
     size_t count = totalSampleCount / samples_per_pass;
     int16_t *buffer = data_in;
     for (int i = ; i < count; i++) {
         data = shine_encode_buffer_interleaved(s, buffer, &written);
         if (write_mp3(written, data, &config) != written) {
             fprintf(stderr, "mp3 encoder && decoder: write error\n");
             return ;
         }
         buffer += samples_per_pass;
     }
     size_t last = totalSampleCount % samples_per_pass;
     if (last != ) {
         int16_t *cache = (int16_t *) calloc(samples_per_pass, sizeof(int16_t));
         if (cache != NULL) {
             memcpy(cache, buffer, last * sizeof(int16_t));
             data = shine_encode_buffer_interleaved(s, cache, &written);
             free(cache);
             if (write_mp3(written, data, &config) != written) {
                 fprintf(stderr, "mp3 encoder && decoder: write error\n");
                 return ;
             }
         }
     }
     /* Flush and write remaining data. */
     data = shine_flush(s, &written);
     write_mp3(written, data, &config);
     /* Close encoder. */
     shine_close(s);
     /* Close the MP3 file */
     fclose(outfile);
     free(data_in);
     double time_interval = calcElapsed(startTime, now());
     if (!quiet)
         printf("time interval: %d ms\n ", (int) (time_interval * ));

     return ;
 }

熟悉我的风格的朋友们，估计一看就清楚了。

也不多做解释，当然了，这份代码是学习mp3编解码的不二之选。

使用示例:

tinymp3 -b 64 input.mp3 ouput.mp3

tinymp3 -b 64 input.wav ouput.mp3

相关参数说明：

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

不做解释，直接上取下项目，cmake一下，你懂的。

项目地址:

https://github.com/cpuimage/tinymp3

前面有不少朋友问到音频重采样库的问题，抽空整理了下speex的resampler。

我想重采样这方面也是够用的了。

项目地址:

https://github.com/cpuimage/speex_resampler

以上，权当抛砖引玉。

另外感谢 热心网友打赏两瓶可乐。

独乐乐，不如众乐乐。

若有其他相关问题或者需求也可以邮件联系俺探讨。

邮箱地址是: 
gaozhihan@vip.qq.com