objective-c - AudioFileOpen无法以读/写权限打开

Question

我正在尝试以编程方式优化使用AudioFileOptimize()而非iTunes或afconvert的软件创建的AAC文件(.m4a)。

但是，当我尝试执行具有读/写权限的AudioFileOpen时，它给我一个错误。即使我手动将POSIX权限设置为0666(每个人均为r / w)，我也只能以读取权限打开。

我正在使用AudioFileOpenUrl描述的here方法并返回“prm？” (kAudioFilePermissionsError)。

这是引发错误的代码:

#import <Cocoa/Cocoa.h>
#import <CoreFoundation/CoreFoundation.h>
#import <AudioToolbox/AudioToolbox.h>
#import "CAXException.h"



int main(int argc, const char * argv[])
{

    int result = 0;

    try {

    //optimize the output file:
    AudioFileID outfile;

    NSURL *outputFileURL = [NSURL fileURLWithPath:@"/DIR/PATH TO.m4a"];

    OSStatus err = AudioFileOpenURL((__bridge CFURLRef)outputFileURL, kAudioFileReadWritePermission, 0, &outfile);
    XThrowIfError(err, "AudioFileOpenURL");

    err = AudioFileOptimize(outfile); //Optimize the file
    XThrowIfError(err, "AudioFileOptimize");

    err = AudioFileClose(outfile);
    XThrowIfError(err, "AudioFileClose");

    } catch (CAXException e) {
        char str[32];
        printf ("CAXException thrown from CoreAudioConverter.mm. : %s, %s\n", e.FormatError(str), e.mOperation);
        result = 1;
    } catch (...) {
        result = 1;
    }

    return result;
}

输出:

CAXException thrown from CoreAudioConverter.mm. : 'prm?', AudioFileOpenURL

如果有人可以帮助，那就太好了!

旁注，是否有人以编程方式将流式提示添加到AAC文件中完成任何工作？

谢谢!

Answer 1

AudioFile Services将不允许对某些文件的写访问:

There is however a limitation when working with MPEG-4 file types which include; .mp4 (kAudioFileMPEG4Type), .m4a (kAudioFileM4AType), .3g2 (kAudioFile3GP2Type) and .3gp (kAudioFile3GPType).

AudioFile does not currently support writing to existing files of these types.

看到:
http://developer.apple.com/library/mac/#qa/qa1676/_index.html