原创文｜Space9
猫耳FM音频与普通音频的差异首先我们发现猫耳FM音频是没有后缀名的音频文件，然后我们通过对比发现猫耳FM音频文件并不是什么加密文件，只是将音频文件、封面图片、弹幕文件合并到了一起（导致其他音频播放器无法识别音频）。
如何分离中间部分的音频文件我们要分离中间部分的音频文件需要获得以下两个信息（文件的开头和结尾）。
猫耳FM的文件头探究 第21-24字节 0014H 0015H 0016H 0017H（4字节）是使用小端存储的开始地址第41-44字节 0028H 0029H 0030H 0031H（4字节）是使用小端存储的结束地址 源码 #include <stdio.h>#include <stdint.h>#include <stdlib.h>#include <string.h>#define CHUNK_SIZE 4096#define HEADER_SIZE 12int main(int argc, const char *argv[]){FILE *inFp = NULL;FILE *outFp = NULL;uint32_t remaining_size;unsigned long i;char buff[CHUNK_SIZE];char file_header[HEADER_SIZE];uint32_t file_start_addr, file_size;if (argc <= 1){printf("no input filen");return 0;}char targetName[strlen(argv[1]) + 10];strncpy(targetName, argv[1], strlen(argv[1]));inFp = fopen(argv[1], "rb");if (inFp == NULL){printf("open file failn");exit(1);}fseek(inFp, 20, SEEK_SET);fread(&file_start_addr, 1, sizeof(file_start_addr), inFp);printf("start:%dn", file_start_addr);fseek(inFp, 40, SEEK_SET);fread(&file_size, 1, sizeof(file_size), inFp);printf("end:%ldn", file_size);fseek(inFp, file_start_addr, SEEK_SET);fread(&file_header, HEADER_SIZE, 1, inFp);if ((file_header[0] == 0x49 && file_header[1] == 0x44 && file_header[2] == 0x33) || (file_header[0] == 0xFF && file_header[1] == 0xfb)){printf("MP3 filen");strcat(targetName, ".mp3");}else if ((file_header[4] == 0x66 && file_header[5] == 0x74 && file_header[6] == 0x79 && file_header[7] == 0x70 && file_header[8] == 0x4D && file_header[9] == 0x34 && file_header[10] == 0x41) || (file_header[0] == 0x4D && file_header[1] == 0x34 && file_header[2] == 0x41 && file_header[3] == 0x20)){printf("M4A filen");strcat(targetName, ".m4a");}else{printf("OTHER filen");strcat(targetName, ".temp");}outFp = fopen(targetName, "wb");if (outFp == NULL){printf("open file failn");exit(1);}fseek(inFp, file_start_addr, SEEK_SET);remaining_size = file_size % CHUNK_SIZE;if (remaining_size != 0){fread(&buff, remaining_size, 1, inFp);fwrite(&buff, remaining_size, 1, outFp);}for (i = 0; i < file_size / CHUNK_SIZE; ++i){fread(&buff, CHUNK_SIZE, 1, inFp);fwrite(&buff, CHUNK_SIZE, 1, outFp);}fclose(inFp);inFp = NULL;fclose(outFp);outFp = NULL;return 0;} 优化代码 #include <stdio.h>#include <stdint.h>#include <stdlib.h>#include <string.h>#define CHUNK_SIZE 4096#define HEADER_SIZE 12int main(int argc, const char *argv[]){FILE *inFp = NULL;FILE *outFp = NULL;uint32_t read_temp_size;char buff[CHUNK_SIZE];char file_header[HEADER_SIZE];uint32_t file_start_addr, file_size;if (argc <= 1){printf("no input filen");return 0;}char targetName[strlen(argv[1]) + 10];strncpy(targetName, argv[1], strlen(argv[1]));inFp = fopen(argv[1], "rb");if (inFp == NULL){printf("open file failn");exit(1);}fseek(inFp, 20, SEEK_SET);fread(&file_start_addr, 1, sizeof(file_start_addr), inFp);printf("start:%dn", file_start_addr);fseek(inFp, 40, SEEK_SET);fread(&file_size, 1, sizeof(file_size), inFp);printf("end:%ldn", file_size);fseek(inFp, file_start_addr, SEEK_SET);fread(&file_header, HEADER_SIZE, 1, inFp);if ((file_header[0] == 0x49 && file_header[1] == 0x44 && file_header[2] == 0x33) || (file_header[0] == 0xFF && file_header[1] == 0xfb)){printf("MP3 filen");strcat(targetName, ".mp3");}else if ((file_header[4] == 0x66 && file_header[5] == 0x74 && file_header[6] == 0x79 && file_header[7] == 0x70 && file_header[8] == 0x4D && file_header[9] == 0x34 && file_header[10] == 0x41) || (file_header[0] == 0x4D && file_header[1] == 0x34 && file_header[2] == 0x41 && file_header[3] == 0x20)){printf("M4A filen");strcat(targetName, ".m4a");}else{printf("OTHER filen");strcat(targetName, ".temp");}outFp = fopen(targetName, "wb");if (outFp == NULL){printf("open file failn");exit(1);}fseek(inFp, file_start_addr, SEEK_SET);while (file_size != 0){/* 使用右移和按位与优化代码 */// read_temp_size = file_size / CHUNK_SIZE ? CHUNK_SIZE : file_size % CHUNK_SIZE;read_temp_size = file_size >> 12 ? CHUNK_SIZE : file_size & (CHUNK_SIZE - 1);fread(&buff, read_temp_size, 1, inFp);fwrite(&buff, read_temp_size, 1, outFp);file_size -= read_temp_size;}fclose(inFp);inFp = NULL;fclose(outFp);outFp = NULL;return 0;} 实现DEMO猫儿转换器 WIN端
https://474b.com/file/20114131-442366646
猫儿转换器 MAC端
https://n802.com/file/20114131-463229588
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