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03-24-2008, 09:39 AM
| #1 |
| Registered User Join Date: Mar 2008
Posts: 6
|  Mixing wav files using ANSI C I'm looking to write a basic Visual C++ ANSI C program which will mix two audio wav files together. The program should operate in a DOS console and should simply request both the input files, the percentage mix, i.e. 50/50 mix etc, and the output filename. The filetype can be a 8 bit mono type. I need some help with what to do, some programming structure as to how I do it. I would also appreciate the code for how to go through the process cos as I say I have no real programming experience to speak of.......... I'd be grateful for anyone's assistance in this, please mail back as soon as you can |
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03-24-2008, 04:11 PM
| #2 | ||
| Hardware Engineer Join Date: Sep 2001
Posts: 1,397
| Quote:
I suggest you start by working-through the C++ Made Easy Tutorial. I also suggest that you get a beginning C+ book. The tutorial is very abbreviated. A beginning book will cover essentially the same topics, but with 350-700 pages of detail and explanation. As you work-through the tutorial, you should be able to see how you can apply what you are learning to your project. Most tutorials and books jump right-into the particular language and are rather light on "general programming concepts" or "structure". Unless you are taking a formal class, you will have to pick-up this stuff as you go along, and do a bit of your own research. You could find books on these subjects, but they would probably be more-advanced books aimed at university-level computer science students. You can find the WAV file spec at Wotsit.org. I assume you know something about digital audio, and how the "wave" is stored as a series of individual samples. Like most technical specifications, it's fairly complicated and you might not understand it the first time you look at it... You will probably need to do some additional research. It will also help to look at some WAV files with a Hex Editor. You will be able to see the file header and the individual sample values. (You will be looking a bytes in hexadecimal format, so you'd have to combine the bytes to see 16-bit samples.) This may not make much sense at first, since most people are not used to working in hex. But, the hex editor will also show the ASCII character for each byte, so you will see the ASCII characters in the header. The hex editor doesn't know which bytes are supposed to represent ASCII characters, but with the spec in-hand, you will know which "characters" are meaningful, and which ones are actually audio data, etc. Quote:
* I'd consider this an "easy project" if you require the two WAV files to have the same format (Don't try to mix a 16-bit, 44.1kHz stereo file with an 8-bit 12kHz file) and if you only use the program for "regular" uncompressed WAV files. A beginning programming student could handle this "assignment" by the end of the semester, and probably sooner. If you wanted the ability to mix different formats and compressed files, I say that's an intermediate-to-advanced project. Last edited by DougDbug; 03-24-2008 at 04:35 PM. | ||
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03-24-2008, 06:53 PM
| #3 |
| Guest  Join Date: Aug 2001
Posts: 4,895
| shouldn't this be added to the FAQ?  |
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04-01-2008, 09:08 AM
| #4 |
| Registered User Join Date: Mar 2008
Posts: 6
| Hi DougDbug, Many thanks for your reply, am still having some difficulties with this. Do you have any more suggestions, parts of this just look very complicated. Are you aware of anyone who's tried doing this in the past |
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04-01-2008, 09:14 AM
| #5 |
| Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England
Posts: 15,686
| It is not trivial to do this - you obviously will have to do some code to access the sound data. Reading wav files is not terribly difficult, but does require a little bit of work. Then comes the actual mixing process, which in a trivial variant is just an averaging algorithm, but for better result you probably need to use a more complex method. -- Mats
__________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers. |
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04-01-2008, 09:38 AM
| #6 |
| Senior software engineer  Join Date: Mar 2007 Location: Portland, OR
Posts: 5,357
| If you don't really have C++ experience, this is going to be hard to do in C++... For opening and reading/writing sound files, look at libsndfile. The API looks complex but you only need a few of the calls. As far as mixing, just make the weighted average of the corresponding signals. If you are mixing 70/30, you would produce output[i] = 0.7 * input1[i] + 0.3 * input2[i]. If that equation looks confusing I wouldn't try to tackle this project. Last edited by brewbuck; 04-01-2008 at 09:41 AM. |
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04-01-2008, 05:31 PM
| #7 |
| Super Moderator  Join Date: Aug 2001
Posts: 7,456
| You just have to add all the samples at any point in time for the duration of the sound and place those in the final mix buffer. Averaging will cause the volumes to all merge on a central overall volume level which is why it's not a good idea. |
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04-02-2008, 08:20 AM
| #8 |
| Registered User Join Date: Mar 2008
Posts: 6
| Thanks Guys for your responses, Was just wondering if anyone knew of any code to do part of this as I may be able to understand it a bit better if I have some code to look at. Have managed to specify the wav files and have got the program to read them in. Am just looking at how to mix them together....it need only be a 50/50 mix |
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04-02-2008, 08:22 AM
| #9 |
| Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England
Posts: 15,686
| Mixing them together should be very easy - just read the raw data for both files, and produce a new WAV file based on the sum of the two [clamping to max and min values of course] -- Mass
__________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers. |
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04-02-2008, 08:25 AM
| #10 |
| Registered User Join Date: Mar 2008
Posts: 6
| Thanks matsp, Will try and do that, will it be ok to mail you if I need any more help |
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04-02-2008, 08:32 AM
| #11 | |
| Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England
Posts: 15,686
| Quote:
Just post here, and someone will answer - that's much quicker than sending me a PM to find that I'm sleeping, eating or otherwise occupied elsewhere. -- Mats
__________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers. | |
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04-02-2008, 09:39 AM
| #12 | |
| Senior software engineer Join Date: Mar 2007 Location: Portland, OR
Posts: 5,357
| Quote:
EDIT: Adding the two samples is a specific instance of mixing: 1.0*x+1.0*y. 0.7*x+0.3*y is another instance. There's nothing different here except the coefficients. | |
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04-12-2008, 02:56 PM
| #13 |
| Registered User Join Date: Mar 2008
Posts: 6
| Hey Guys, Am still trying to do this C program, have been making some progress but am still finding some of what are probably the easiest things in C really difficult....... Could someone have a little look over my code so far and tell me where I'm going wrong. This is the code I was looking to open a audio file in C, was trying to get it to output the contents of the file but wasn't having much luck...... Code:
#include <stdio.h>
#include <avg_bytes_sec>
#include <format_length>
#include <format_tag>
#include <channels>
#include <sample_rate>
#include <block_align>
#include <bits_per_sample>
#include <data_size>
#include <sound_buffer>
#include <string.h>
public:
char* myPath;
int myChunkSize;
int mySubChunkSize;
short myFormat;
short myChannels;
int mySampleRate;
int myByteRate;
short myBlockAlign;
short myBitsPerSample;
~ DING.WAVForIO()
{
delete myPath;
myChunkSize = NULL;
mySubChunk1Size = NULL;
myFormat = NULL;
myChannels = NULL;
mySampleRate = NULL;
myByteRate = NULL;
myBlockAlign = NULL;
myBitsPerSample = NULL;
myDataSize = NULL;
}
void Load_Wave_File(char *fname)
{
FILE *fp;
fp = fopen("DING.WAV","rb");
if (fp)
{
BYTE id[4], *sound_buffer; //four bytes to hold 'RIFF'
DWORD size; //32 bit value to hold file size
short format_tag, channels, block_align, bits_per_sample; //our 16 values
DWORD format_length, sample_rate, avg_bytes_sec, data_size, i; //our 32 bit values
fread(id, sizeof(BYTE), 4, fp); //read in first four bytes
if (!strcmp(id, "RIFF")) { //we had 'RIFF' let's continue
fread(size, sizeof(DWORD), 1, fp); //read in 32bit size value
fread(id, sizeof(BYTE), 4, fp); //read in 4 byte string now
if (!strcmp(id,"WAVE"))
{ //this is probably a wave file since it contained "WAVE"
fread(id, sizeof(BYTE), 4, fp); //read in 4 bytes "fmt ";
fread(&format_length, sizeof(DWORD),1,fp);
fread(&format_tag, sizeof(short), 1, fp); //check mmreg.h (i think?) for other
// possible format tags like ADPCM
fread(&channels, sizeof(short),1,fp); //1 mono, 2 stereo
fread(&sample_rate, sizeof(DWORD), 1, fp); //like 44100, 22050, etc...
fread(&avg_bytes_sec, sizeof(short), 1, fp); //probably won't need this
fread(&block_align, sizeof(short), 1, fp); //probably won't need this
fread(&bits_per_sample, sizeof(short), 1, fp); //8 bit or 16 bit file?
fread(id, sizeof(BYTE), 4, fp); //read in 'data'
fread(&data_size, sizeof(DWORD), 1, fp); //how many bytes of sound data we have
sound_buffer = (BYTE *) malloc (sizeof(BYTE) * data_size); //set aside sound buffer space
fread(sound_buffer, sizeof(BYTE), data_size, fp); //read in our whole sound data chunk
}
else
printf("Error: RIFF file but not a wave file\n");
}
else
printf("Error: not a RIFF file\n");
}
}
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04-12-2008, 03:43 PM
| #14 |
| Cat without Hat  Join Date: Apr 2003
Posts: 8,433
| Well, first you should be clear on whether you want to program C or C++. Your code consists of a curious mix of elements of both languages, with the C++ parts used incorrectly.
__________________ All the buzzt!  CornedBee"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code." - Flon's Law |
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04-13-2008, 09:47 AM
| #15 |
| Registered User Join Date: Mar 2008
Posts: 6
| Hi, Was looking to code it in C, not C++.....  What do I need to do change it over to C, is it a big change!! Can you give me some info |
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