C++ RSS C++ RSS

Writing PCM as raw data in C/C++ in Windows

Please support our C++ advertiser: Intel Parallel Studio Home
Thread Solved

•
•
Join Date: Jul 2005
Posts: 14
Reputation: fluidDelusions is an unknown quantity at this point 
Solved Threads: 0
fluidDelusions fluidDelusions is offline Offline
Newbie Poster

Writing PCM as raw data in C/C++ in Windows

 
0
  #1
Jan 15th, 2006
Hello!
I'm having a very difficult time with this problem. What I'm trying to do is generate a sine wave for a specific frequency and output it as raw pcm data to a file.
The sine wave is generated as follows:

C++ Syntax (Toggle Plain Text) 
  1.  samples[i]=static_cast<int>(32767 * amplitude * sin(static_cast<double>(i)*scale) );

where scale = 2*PI/sample_rate.

And to write a specific sample in raw format, I'm first converting it to an array of char in little endian byte order, like this:

C++ Syntax (Toggle Plain Text) 
  1. void writeInt(std::ofstream& out, int integer, int num_bytes)
  2. {
  3. 	int y = (integer);
  4. 	for(int i=0; i<num_bytes; i++)
  5. 	{
  6. 		int x = y&255;
  7. 		out.put(x);
  8. 		y = y>>8;
  9. 	}
  10. }

Now, this is fine in Linux (using gcc). I am able to play a smooth frequency. The problem is when I try to run the same code under Windows (compiled with mingw or bcc32), I get a very distorted sounding wave. Clearly, the data is not being written or converted properly. So to get right down to it, what is causing this difference between Linux and Windows? And, if at all possible, how do I do this the right way in Windows?
Thanks for your consideration!
Reply With Quote Quick reply to this message  
•
•
Join Date: Dec 2005
Posts: 5,850
Reputation: Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute 
Solved Threads: 749
Team Colleague
Salem's Avatar
Salem Salem is offline Offline
Void main'ers are DOOMed

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #2
Jan 15th, 2006
Well did you open the file for output in binary mode?
Did you check the sizes of the file on the two different systems was the same?
Have you copied a file generated on your Linux box to the windows box, and tried to play that?
Reply With Quote Quick reply to this message  
•
•
Join Date: Jul 2005
Posts: 14
Reputation: fluidDelusions is an unknown quantity at this point 
Solved Threads: 0
fluidDelusions fluidDelusions is offline Offline
Newbie Poster

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #3
Jan 15th, 2006
•
•
•
•
Originally Posted by Salem
Well did you open the file for output in binary mode?
Did you check the sizes of the file on the two different systems was the same?
Have you copied a file generated on your Linux box to the windows box, and tried to play that?
Yes, yes, and yes. I can make a wave file out of the linux and the windows pcm data, and the linux sounds correct on both linux and windows. I can make a wave in windows and it sounds the same in windows and linux (scratchy and bad). I can make the raw data in windows, and use sox to convert that to a wave in linux, and it sounds the same on linux as it does windows.
The difference is happening at the conversion from integer to bytes, I'm almost sure of that. Another thing: in linux, you can just call ostream.write((char*)(&samples[i]),2) and this will work fine. Again, it doesn't work in windows. Why?
Reply With Quote Quick reply to this message  
•
•
Join Date: Jul 2005
Posts: 14
Reputation: fluidDelusions is an unknown quantity at this point 
Solved Threads: 0
fluidDelusions fluidDelusions is offline Offline
Newbie Poster

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #4
Jan 15th, 2006
Uh, heh heh. Problem solved. I wasn't opening the ofstream for binary output. Thanks Salem. I'm so ashamed...
Reply With Quote Quick reply to this message  
•
•
Join Date: Dec 2005
Posts: 5,850
Reputation: Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute Salem has a reputation beyond repute 
Solved Threads: 749
Team Colleague
Salem's Avatar
Salem Salem is offline Offline
Void main'ers are DOOMed

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #5
Jan 15th, 2006
> y = y>>8;
Right shift of negative numbers is implementation defined.
On some systems, the sign bit is propagated
11110000 would become 11111000

and on others zero is inserted.
11110000 would become 01111000
Reply With Quote Quick reply to this message  
•
•
Join Date: Jul 2005
Posts: 14
Reputation: fluidDelusions is an unknown quantity at this point 
Solved Threads: 0
fluidDelusions fluidDelusions is offline Offline
Newbie Poster

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #6
Jan 15th, 2006
That might be true, but then I had tried using standard division, and it did the exact same thing...
Reply With Quote Quick reply to this message  
•
•
Join Date: Apr 2008
Posts: 1
Reputation: ims is an unknown quantity at this point 
Solved Threads: 0
ims ims is offline Offline
Newbie Poster

Re: Writing PCM as raw data in C/C++ in Windows

 
0
  #7
Apr 4th, 2008
Hi,
I am facing the same problem as fluidDelusions.
I can make a wave file out of the linux and the windows pcm data, and the linux sounds correct on both linux and windows. I can make a wave in windows and it sounds the same in windows and linux (scratchy and bad).
If a play the recordfile which is PCM data, 16 bit mono, rate 8000 using the API, it plays fine, bu when i add wave header to it, it becomes bad and scratchy. I am using the same code to write wavheader in Linux and there it works perfectly fine. What can be the problem?
I am in urgent need of the reply. Kindly reply As soon as possible.

Thanks
IMS
Reply With Quote Quick reply to this message  
Reply

Quick Reply to Thread
This thread has been marked solved.
Perhaps start a new thread instead?
•
•
•
•
•
•
•
•
Message:
•
•
•
•



Similar Threads
Other Threads in the C++ Forum
Thread Tools Search this Thread



api array based beginner binary c++ c/c++ calculator char char* class classes code compile compiler console conversion count delete deploy desktop directshow dll download dynamic dynamiccharacterarray email encryption error file forms fstream function functions game givemetehcodez google graph gui homeworkhelp homeworkhelper iamthwee ifstream input int integer java lib linkedlist linker linux list loop looping loops map math matrix memory news numbertoword output parameter pointer problem program programming project proxy python random read recursion recursive reference return rpg sorting string strings struct temperature template templates test text text-file tree unix url variable vector video visualstudio win32 windows winsock word wordfrequency wxwidgets
About Us | Contact Us | Advertise | DaniWeb | Acceptable Use Policy | RSS Feed

©2003 - 2009 DaniWeb® LLC