我正在尝试向 nweb 添加一项功能，使其能够将 MIDI .mid 文件渲染为 .wav 声音文件，以便具有内置 .wav 播放器的浏览器(例如 Chrome)可以播放它们。我有 nweb 但除此之外我完全被难住了。帮助将不胜感激!
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BUFSIZE 8096
#define ERROR 42
#define SORRY 43
#define LOG 44
struct {
char *ext;
char *filetype;
} extensions [] = {
{"gif", "image/gif" },
{"jpg", "image/jpeg"},
{"jpeg","image/jpeg"},
{"png", "image/png" },
{"zip", "image/zip" },
{"gz", "image/gz" },
{"tar", "image/tar" },
{"htm", "text/html" },
{"html","text/html" },
{"mp3","music/mp3"},
{0,0} };
void log(int type, char *s1, char *s2, int num)
{
int fd ;
char logbuffer[BUFSIZE*2];
switch (type) {
case ERROR: (void)sprintf(logbuffer,"ERROR: %s:%s Errno=%d exiting pid=%d",s1, s2, errno,getpid()); break;
case SORRY:
(void)sprintf(logbuffer, "<HTML><BODY><H1>nweb Web Server Sorry: %s %s</H1></BODY></HTML>\r\n", s1, s2);
(void)write(num,logbuffer,strlen(logbuffer));
(void)sprintf(logbuffer,"SORRY: %s:%s",s1, s2);
break;
case LOG: (void)sprintf(logbuffer," INFO: %s:%s:%d",s1, s2,num); break;
}
/* no checks here, nothing can be done a failure anyway */
if((fd = open("nweb.log", O_CREAT| O_WRONLY | O_APPEND,0644)) >= 0) {
(void)write(fd,logbuffer,strlen(logbuffer));
(void)write(fd,"\n",1);
(void)close(fd);
}
if(type == ERROR || type == SORRY) exit(3);
}
/* this is a child web server process, so we can exit on errors */
void web(int fd, int hit)
{
int j, file_fd, buflen, len;
long i, ret;
char * fstr;
static char buffer[BUFSIZE+1]; /* static so zero filled */
ret =read(fd,buffer,BUFSIZE); /* read Web request in one go */
if(ret == 0 || ret == -1) { /* read failure stop now */
log(SORRY,"failed to read browser request","",fd);
}
if(ret > 0 && ret < BUFSIZE) /* return code is valid chars */
buffer[ret]=0; /* terminate the buffer */
else buffer[0]=0;
for(i=0;i<ret;i++) /* remove CF and LF characters */
if(buffer[i] == '\r' || buffer[i] == '\n')
buffer[i]='*';
log(LOG,"request",buffer,hit);
if( strncmp(buffer,"GET ",4) && strncmp(buffer,"get ",4) )
log(SORRY,"Only simple GET operation supported",buffer,fd);
for(i=4;i<BUFSIZE;i++) { /* null terminate after the second space to ignore extra stuff */
if(buffer[i] == ' ') { /* string is "GET URL " +lots of other stuff */
buffer[i] = 0;
break;
}
}
for(j=0;j<i-1;j++) /* check for illegal parent directory use .. */
if(buffer[j] == '.' && buffer[j+1] == '.')
log(SORRY,"Parent directory (..) path names not supported",buffer,fd);
if( !strncmp(&buffer[0],"GET /\0",6) || !strncmp(&buffer[0],"get /\0",6) ) /* convert no filename to index file */
(void)strcpy(buffer,"GET /index.html");
/* work out the file type and check we support it */
buflen=strlen(buffer);
fstr = (char *)0;
for(i=0;extensions[i].ext != 0;i++) {
len = strlen(extensions[i].ext);
if( !strncmp(&buffer[buflen-len], extensions[i].ext, len)) {
fstr =extensions[i].filetype;
break;
}
}
if(fstr == 0) log(SORRY,"file extension type not supported",buffer,fd);
if(( file_fd = open(&buffer[5],O_RDONLY)) == -1) /* open the file for reading */
log(SORRY, "failed to open file",&buffer[5],fd);
log(LOG,"SEND",&buffer[5],hit);
(void)sprintf(buffer,"HTTP/1.0 200 OK\r\nContent-Type: %s\r\n\r\n", fstr);
(void)write(fd,buffer,strlen(buffer));
/* send file in 8KB block - last block may be smaller */
while ( (ret = read(file_fd, buffer, BUFSIZE)) > 0 ) {
(void)write(fd,buffer,ret);
}
#ifdef LINUX
sleep(1); /* to allow socket to drain */
#endif
exit(1);
}
int main(int argc, char **argv)
{
int i, port, pid, listenfd, socketfd, hit;
size_t length;
static struct sockaddr_in cli_addr; /* static = initialised to zeros */
static struct sockaddr_in serv_addr; /* static = initialised to zeros */
if( argc < 3 || argc > 3 || !strcmp(argv[1], "-?") ) {
(void)printf("hint: nweb Port-Number Top-Directory\n\n"
"\tnweb is a small and very safe mini web server\n"
"\tnweb only servers out file/web pages with extensions named below\n"
"\t and only from the named directory or its sub-directories.\n"
"\tThere is no fancy features = safe and secure.\n\n"
"\tExample: nweb 8181 /home/nwebdir &\n\n"
"\tOnly Supports:");
for(i=0;extensions[i].ext != 0;i++)
(void)printf(" %s",extensions[i].ext);
(void)printf("\n\tNot Supported: URLs including \"..\", Java, Javascript, CGI\n"
"\tNot Supported: directories / /etc /bin /lib /tmp /usr /dev /sbin \n"
"\tNo warranty given or implied\n\tNigel Griffiths nag@uk.ibm.com\n"
);
exit(0);
}
if( !strncmp(argv[2],"/" ,2 ) || !strncmp(argv[2],"/etc", 5 ) ||
!strncmp(argv[2],"/bin",5 ) || !strncmp(argv[2],"/lib", 5 ) ||
!strncmp(argv[2],"/tmp",5 ) || !strncmp(argv[2],"/usr", 5 ) ||
!strncmp(argv[2],"/dev",5 ) || !strncmp(argv[2],"/sbin",6) ){
(void)printf("ERROR: Bad top directory %s, see nweb -?\n",argv[2]);
exit(3);
}
if(chdir(argv[2]) == -1){
(void)printf("ERROR: Can't Change to directory %s\n",argv[2]);
exit(4);
}
/* Become daemon + unstoppable and no zombies children (= no wait()) */
if(fork() != 0)
return 0; /* parent returns OK to shell */
(void)signal(SIGCLD, SIG_IGN); /* ignore child death */
(void)signal(SIGHUP, SIG_IGN); /* ignore terminal hangups */
for(i=0;i<32;i++)
(void)close(i); /* close open files */
(void)setpgrp(); /* break away from process group */
log(LOG,"nweb starting",argv[1],getpid());
/* setup the network socket */
if((listenfd = socket(AF_INET, SOCK_STREAM,0)) <0)
log(ERROR, "system call","socket",0);
port = atoi(argv[1]);
if(port < 0 || port >60000)
log(ERROR,"Invalid port number (try 1->60000)",argv[1],0);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(port);
if(bind(listenfd, (struct sockaddr *)&serv_addr,sizeof(serv_addr)) <0)
log(ERROR,"system call","bind",0);
if( listen(listenfd,64) <0)
log(ERROR,"system call","listen",0);
for(hit=1; ;hit++) {
length = sizeof(cli_addr);
if((socketfd = accept(listenfd, (struct sockaddr *)&cli_addr, &length)) < 0)
log(ERROR,"system call","accept",0);
if((pid = fork()) < 0) {
log(ERROR,"system call","fork",0);
}
else {
if(pid == 0) { /* child */
(void)close(listenfd);
web(socketfd,hit); /* never returns */
} else { /* parent */
(void)close(socketfd);
}
}
}
}
最佳答案
您可以使用 FluidSynth ( http://www.fluidsynth.org/ )。它带有一个 C 库。 API 记录在此处:
http://fluidsynth.sourceforge.net/api/
您可以使用以下内容渲染 MIDI 文件:
#include <fluidsynth.h>
// ...
fluid_settings_t* settings = new_fluid_settings()
// Render at 44.1KHz.
fluid_settings_setnum(settings, "synth.sample-rate", 44100);
fluid_synth_t* synth = new_fluid_synth(settings)
// Set volume to 70%. High volume levels may cause clipping.
fluid_synth_set_gain(synth, 0.7f);
// Quality of interpolation. This is high quality. Needs more CPU.
fluid_synth_set_interp_method(synth, -1, FLUID_INTERP_7THORDER);
// Which soundfont file to use.
fluid_synth_sfload(synth, "soundfont.sf2", true);
fluid_player_t* player = new_fluid_player(synth);
// Load a MIDI file.
fluid_player_add(player, "midi_file.mid");
// Start "playing" the MIDI file. This simply prepares the file for
// rendering, it doesn't really "play" anything.
fluid_player_play(player);
注意:您可以使用 fluid_player_add_mem() 代替 fluid_player_add() 将 MIDI 字节提供给 FluidSynth。这取决于您如何从源中获取 MIDI 数据。
上面初始化并设置了一个合成器和一个播放器。请注意，您需要一个 soundfont 文件(SF2 格式)，否则您无法渲染任何内容。 SF2 文件包含各种 MIDI 乐器的音频数据。假设您的 MIDI 文件以 GM 标准(通用 MIDI)为目标，您将需要找到一个 GM soundfont(或 GS 一个；GS 是 GM 的扩展，具有更多乐器，一些 MIDI 文件需要它。)有许多免费的 SF2 soundfonts可用，大小不一(范围在 2MB 到几 GB 之间。)
要实际进行渲染并取回音频数据，您可以调用 fluid_synth_write_float()(对于浮点样本)或 fluid_synth_write_s16()(对于整数样本)。之后，使用fluid_player_get_status()检查MIDI文件是否结束播放。
获得音频样本后，您可以以 WAV 格式提供它们，或使用编码器(如 libvorbisfile 库)将样本压缩为 Ogg/Vorbis 音频。或者可能使用 libmpg123 来提供 MP3 音频。
关于创建一个 wav。来自 MIDI 文件的文件并将其提供给 NWEB，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30290665/