Re: Help with AudioFileGetProperty
Re: Help with AudioFileGetProperty
- Subject: Re: Help with AudioFileGetProperty
- From: Gilbert Mackall <email@hidden>
- Date: Tue, 25 Feb 2003 18:18:53 -0500
Tommy,
Thanks for the help. After a few changes here are the results of
opening an AIFF formated file created with QuickTime and the code used
to get them.
PATH = /Users/gilbertmackall/Desktop/VAM_greeting.aif
SampleRate 44100.000000
FormatID 1819304813
FormatFlags 14
BytesPerPacket 2
FramesPerPacket 1
BytesPerFrame 2
ChannelsPerFrame 1
- (IBAction)getFile:(id)sender
{
int result;
NSString *path;
FSRef fileRef;
AudioFileID fileID;
UInt32 theSize;
UInt32 isWritable;
OSStatus osStatus = noErr;
AudioStreamBasicDescription basicDescription;
NSArray *fileTypes = [NSArray
arrayWithObjects:@"AIFF",@"aif",@"AIFC",@"WAVE",@"wav",nil];
NSOpenPanel *oPanel = [NSOpenPanel openPanel];
[oPanel setAllowsMultipleSelection:NO];
result = [oPanel runModalForTypes:fileTypes];
if (result == NSOKButton)
{
NSArray *filesToOpen = [oPanel filenames];
path = [filesToOpen objectAtIndex:0];
printf("%s \n",[path cString]);
FSPathMakeRef([path fileSystemRepresentation],&fileRef,NULL);
AudioFileOpen(&fileRef, fsRdPerm, 0, &fileID);
osStatus = AudioFileGetPropertyInfo(fileID,
kAudioFilePropertyDataFormat, &theSize, & isWritable);
if( osStatus == noErr )
{
// basicDescription = (AudioStreamBasicDescription *
)malloc(sizeof(AudioStreamBasicDescription));
osStatus =
AudioFileGetProperty(fileID,kAudioFilePropertyDataFormat,&theSize,&basic
Description);
if( osStatus == noErr )
{
printf("SampleRate %f\n",basicDescription.mSampleRate);
printf("FormatID %ld\n",basicDescription.mFormatID);
printf("FormatFlags
%ld\n",basicDescription.mFormatFlags);
printf("BytesPerPacket
%ld\n",basicDescription.mBytesPerPacket);
printf("FramesPerPacket
%ld\n",basicDescription.mFramesPerPacket);
printf("BytesPerFrame
%ld\n",basicDescription.mBytesPerFrame);
printf("ChannelsPerFrame
%ld\n",basicDescription.mChannelsPerFrame);
}
}
}
On Monday, February 24, 2003, at 11:25 PM, Tommy Braas wrote:
Gilbert,
Void pointers is the C way of achieving a generic way of sending
untyped data. Any pointer can be a void pointer. There shouldn't be a
need to cast something to a void pointer, there is, however, a need to
cast a pointer from a void pointer to some other kind of pointer.
The simplest way of changing your code would be to change the
following lines;
AudioFileOpen(fileRef, fsRdPerm, 0, fileID);
AudioFileGetProperty(fileID,kAudioFilePropertyDataFormat,theSize,basicD
escription);
to
// the fourth parameter needs to be a pointer, prepend
ampersand to any datatype to make it a pointer to that type
AudioFileOpen(fileRef, fsRdPerm, 0, &fileID);
// the fourth parameter needs to be a pointer, prepend
ampersand to any datatype to make it a pointer to that type
AudioFileGetProperty(fileID, kAudioFilePropertyDataFormat,
theSize, &basicDescription);
The reason why that should work, without retrieving the size properly
first, is that the AudioStreamBasicDescription is fixed in size. Any
property that has a variable size should be retrieved using the steps
outlined below.
The way the various get property methods are supposed to be used, as
far as I know, is that first you query the API to get the size of the
data, then you get the data.
So, you would do the following in the general case (which covers ALL
values and types for the property data returned by a query);
UInt32 theSize;
void *theData;
UInt32 isWritable;
OSStatus osStatus = noErr;
osStatus = AudioFileGetPropertyInfo(inAudioFile, inPropertyID,
&theSize, &writable);
if( osStatus == noErr )
{
// allocate enough space to hold the data
theData = malloc( theSize * sizeof(char));
osStatus = AudioFileGetProperty(inAudioFile, inPropertyID, &theSize,
theData);
if( osStatus == noErr )
{
// the data is valid
// do something with the data
// cast 'theData' to the type that was returned by
the property, and access its fields
}
}
Some properties are writable using the AudioFileSetProperty(...), and
the 'writable' variable will be true (1) if the specific property is
writable.
I would change your code to the following;
- (IBAction)getFile:(id)sender
{
int result;
NSString *path;
FSRef *fileRef;
AudioFileID fileID;
UInt32 theSize;
UInt32 isWritable;
AudioStreamBasicDescription *basicDescription;
OSStatus osStatus = noErr;
NSArray *fileTypes = [NSArray
arrayWithObjects:@"AIFF",@"AIFC",@"WAVE",@"wav",nil];
NSOpenPanel *oPanel = [NSOpenPanel openPanel];
[oPanel setAllowsMultipleSelection:NO];
result = [oPanel runModalForTypes:fileTypes];
if (result == NSOKButton)
{
NSArray *filesToOpen = [oPanel filenames];
path = [filesToOpen objectAtIndex:0];
NSLog(@"%@ \n", path);
FSPathMakeRef([path fileSystemRepresentation], fileRef, NULL);
AudioFileOpen(fileRef, fsRdPerm, 0, &fileID);
osStatus = AudioFileGetPropertyInfo(fileID,
kAudioFilePropertyDataFormat, &theSize, & isWritable);
if( osStatus == noErr )
{
basicDescription = (AudioStreamBasicDescription *
)malloc(sizeof(AudioStreamBasicDescription));
osStatus = AudioFileGetProperty(fileID,
kAudioFilePropertyDataFormat, &theSize, basicDescription);
if( osStatus == noErr )
{
// your data should be contained and accessible
through 'basicDescription' here
}
}
}
}
I hope this helps you out!
Best regards,
Tommy Braas
deep sea software
On Monday, Feb 24, 2003, at 18:48 US/Pacific, Gilbert Mackall wrote:
I am having a problem in understanding how the AudioFileGetProperty
function is passed a pointer for the AudioStreamBasicDescription of
the file I have selected. Below is the section of code I am having
problems with. In reading AudioFile.h it states:
AudioFileGetProperty( AudioFileID inAudioFile,
AudioFilePropertyID inPropertyID,
UInt32 *ioDataSize,
void *outPropertyData);
My problem seems to be that I am not understanding, how to pass a
void pointer.
- (IBAction)getFile:(id)sender
{
int result;
NSString *path;
FSRef *fileRef;
AudioFileID fileID;
UInt32 *theSize;
AudioStreamBasicDescription basicDescription;
NSArray *fileTypes = [NSArray
arrayWithObjects:@"AIFF",@"AIFC",@"WAVE",@"wav",nil];
NSOpenPanel *oPanel = [NSOpenPanel openPanel];
[oPanel setAllowsMultipleSelection:NO];
result = [oPanel runModalForTypes:fileTypes];
if (result == NSOKButton)
{
NSArray *filesToOpen = [oPanel filenames];
path = [filesToOpen objectAtIndex:0];
printf("%s \n",[path cString]);
FSPathMakeRef([path fileSystemRepresentation],fileRef,NULL);
AudioFileOpen(fileRef, fsRdPerm, 0, fileID);
AudioFileGetProperty(fileID,kAudioFilePropertyDataFormat,theSize,basic
Description);
}
}
_______________________________________________
coreaudio-api mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/coreaudio-api
Do not post admin requests to the list. They will be ignored.
_______________________________________________
coreaudio-api mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/coreaudio-api
Do not post admin requests to the list. They will be ignored.
Gilbert Mackall
_______________________________________________
coreaudio-api mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/coreaudio-api
Do not post admin requests to the list. They will be ignored.