Thread: File format converter, wav to aiff.

Why are you making this so insanely complicated? Why do you want to rewrite the file in place? I don't know of a single conversion utility (sound, video, image or otherwise) that does that. And I wouldn't use such a tool -- if it crashes, I've lost my original file.

Originally Posted by Subsonics

Brewbuck, if it´s complicated it´s because I´m new to this. What would be a better way of doing this in your oppinion? And at some point I would have to rewrite over the old file or end up with two files right?

I don't think it's that complicated. It sounds like you're on the right track by reading the WAV header into a structure then writing that out as an AIFF header. I just wouldn't suggest complicating it by trying to do everything in place. Just use a temporary file. If you insist on overwriting the original, then do this after the conversion by deleting it then renaming the temporary file.

In any case, rewriting directly in place is not only more complicated, it's dangerous because a bug in your program can trash the input file, and that will probably anger the user If you are replacing the original, at least provide a way to turn this feature off in case the user is paranoid. Then you can always say "I warned you..."

Reading the entire WAV into memory isn't the best plan either, since that means the size of file you can convert is limited by available RAM.

Originally Posted by Subsonics

Yes, point taken. Using a temp file seems like a better way of doing this. I think it´s safe to say that it will save me from some headache while testing my code as well.

Yep!

So I guess doing it in portions, performing any necessary conversion then writing to the temp file is the way to do it.

Maybe 1MB at a time... Anything is reasonable, just not "potentially infinite." I've seen some extremely large WAV files.

Originally Posted by Subsonics

Getting into more details. What whould be the best way of getting the data from the file into the specific struct members that are not constants? For now I have set up a for loop that fgetc´s the first 44 bytes and assigns them into a char array. I then memcpy from the array into the appropriate struct members. The memcpy have the side effect of changing the endianess as well which is welcomed in this case.

Is there a more effective way of doing this? I have tried to make an array of just the struct members I want to write to but got an error message, is that at all possible? It would be nice if I could some how get the data from the file into the struct using a loop or something.

memcpy() shouldn't change endianness. Can you give more details and/or code?

Here is the first part where I read 44 bytes into the array fileName (re-used BTW, as I use it for file name as well). (This code is losely based on Noir´s code in the sticky about development process BTW.)

Code:

	// collect data from fileheader in file: fileName.
	FILE *fp = fopen( fileName, "r" ); 

	if ( fp ) {
		for(i = 0; i < 44; i++) {
			fileName[i] = fgetc( fp ); 
	    }
	    fclose( fp );
	} else {
		perror( "error opening the file" );
	}

Here is the part where I memcpy from the array. (it´s just the first struct of three but it should do to demonstrate what happens):

Code:

	// Add data to FORM chunk
	FormAIFFChunk form = {"FORM", 0, "AIFF"};
	memcpy(&form.ckDataSize, &fileName[4], 4);	
	printf("%s%d%s", form.ckID, form.ckDataSize, form.formType);

OT:

I managed to collect all struct members that I plan to write to (6 in total) in an array BTW, so I might try to somehow automate the assigning from the file in a for loop instead of using the array and memcpy later on.

There's no endian reversing going on there -- what proof do you have that it's happening? Also, what's your platform?

What I did was trying the program on a wav file and passed stdout to a new file. I then opened both the the original wav and the file the program gave me into an hexeditor. I set the hexeditor to display the wav as little endian and compared the filesize (that is byte 4-8) and my file. The output from the program is a string and I changed %d to %x to get a hexnumber. The wave displays: 6409 | 6800 | and the string in my file displays: 680964.

I´m using a mac BTW, but it´s an intel one.