Thread: C program to play a sound

I'm new to C but I've been using linux for years -- I would NEVER recommend it to anyone, however, because it has such a ridiculous learning curve attached. But once you're comfortable windows looks like chintzy junk...

Anyway I presume you want play to be a function from some library. I don't know if such a thing exists for linux or windows, but you could look around. Linux C uses GNU glibc, if you haven't yet, see the official docs:
www.delorie.com/gnu/docs/glibc/libc_toc.html
Which includes an index to all standard functions.
Otherwise try execvp("mpg123 file.mp3", NULL);

ps. I hate to mention perl...

I'm pretty sure that the example you gave will try to execute a program called "mpg123 file.mp3", instead of executing a program called "mpg123" and passing "file.mp3" as a parameter.

A simple-ish way to do this is to use

Code:

system("program file.mp3");

where system() is in <stdlib.h> and program is the program you wish to use to open the file. I have no idea what mp3 player(s) you might have; you'll want to check. If you're using KDE, you might start with

Code:

system("konqueror file.mp3");

BTW -- I'd recommend Linux to someone who is willing to learn a little bit. If you don't like it, you can always switch back.

Well, you'll have to use an external library of some sort. The SDL along with SMPEG, for example. (There are probably easier ways, but I don't know of them.)

[edit] Of course, there are online tutorials and such so you could probably find code almost already-written for you.
http://www.gamedev.net/community/for...opic_id=348801
http://listas.apesol.org/pipermail/s...er/059216.html
[/edit]

Either way, it's going to be quite difficult to do this. If you know how to do it in Java, by all means try it. Just make sure your Linux system can run Java programs.

DWK was right about my invocation of "execvp" being wrong -- hopefully i'm about to correct myself.

If your problem with using "system" or "exec" is that you can't stop playback after it's started, then I have your solution (I once made a perl/Tk mp3 app where this figured in). Linux uses process id's ("pid"s) to track all running processes (see a list with "ps"), and you can signal the mp3 playing process to do different things with it's pid.

If you use a simple console based app like mpg123, you can call it without any pop-up windows popping up, etc -- it just plays the file. Then get the pid and kill it when you want. In perl "system" forks a process automatically and returns you the new pid (easy). In C, running a separate program with "system" and "exec" does NOT give you a new pid -- so if you kill the "mpg123" process you will kill your entire program. So you have to fork a process (=what I learned about C today).

Anyway, the following code will play a song until you hit ENTER, then it kills mpg123 (stopping the playback) and leaves a message.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> // for execlp

int main () {
        pid_t x;      // a special kind of int
        char kil[20] = "kill -s 9 ";

        x = fork();   /* now there's actually two "x"s:
if fork succeeds, "x" to the CHILD PROCESS is the return value of fork (0)
and "x" to the PARENT PROCESS is the actual system pid of the child process.*/
        
        if (x < 0) {  // just in case fork fails 
                puts("fork failure");
                exit(-1);
        }   
        else if (x == 0) { // therefore this block will be the child process 
                execlp("mpg123", "mpg123", "-q", "/songs/bertha.mp3", 0); 
        }                   // see GNU docs, "system" also works                
        else {  printf("from parent: mpg123 is pid %d\nENTER to quit\n", x);
                sprintf(kil,"%s%d",kil,x);
                getchar();  // wait for user input
                system(kil);
                printf("All ");
        }       /* witness that the "else if" and "else" blocks are both executed here in parallel. The "else" 
   (parent) block is continuous with the rest of the program (since the PARENT PROCESS is actually
   the program itself) so... */
        printf("done.\n");
        exit(0);
}

Get it? Anyway, that might be all you need.

I'm new to C, but I don't think you can do it without fork for a couple of reasons (mostly the first one):

(1) without fork, the pid of your program and the pid of the system command (mpg123) will be the same, meaning if you kill one, you kill everything.

(2) without fork, mpg123's console output (even if there is none, which is what the "-q" switch does) seems to occupy the terminal, meaning without a GUI there is no way to control the program while mpg123 runs. You could "background" the command (add an "&" to the end, eg. mpg123 -q song.mp3 & -- this only works via "system"), but you still won't get a new pid. Likewise, you could create a pipe and funnel off mpg123's stdout...this is even more complicated and doesn't work because of (1), again.

Anyway, good luck, fork seems like a useful thing to learn, which is what got me into this i guess. (Maybe some pro will come along and wisely contradict).

ps. yes, the child sends the command, the parent (which is really the program itself) kills it.

"You could probably use the kill() function instead of invoking an extra call to system() I believe."

Yes, next time i will, promise.

One of the great things about C/C++ is you can use library's to add functions.
As one has already posted, SDL or FMOD library can be called from a C program.
Without using a shell and having to kill a process.

With these library's, not only can you play WAV, MP3, etc. but have other controls over the sound, like volume, tone, speed. Can start and stop the sound at any point durring playback.

I used both of the above libraries with C.

Look at this SDL example http://www.libsdl.org/intro.en/usingsound.html

You need to install the mpg123-*.rpm package(s). [Only the binaries are necessary. If there isn't one in your current distribution, you can probably find one on the web, for example here: http://rpmfind.net/linux/rpm2html/se...p?query=mpg123

--
Mats

For simple playback of sounds, if you're developing for KDE4, you can use Phonon, which I've heard is pretty nice to work with.

Other than that, there's a multitude of sound libraries, like SDL's sound parts, OpenAL, etc. These are low-level; for high-level playback, there's e.g. Xinelib or gstreamer.