iPhone: get duration of an audio file

Question

Hi,

What is the easiest way to get a duration of an audio file?

I could create an object of AVAudioPlayer, initialize it with URL and than get the duration, but this way is too long. Is there an easier way?

Thanks.

Answer 1

If you know anything about the audio file in question (samplerate, bitdepth, channel count), and it's an uncompressed format (WAV/AIFF), then you can calculate the /approximate/ duration from the filesize:

length_in_seconds = (file_length-guess_100_bytes_for_header) / (samplerate*(bitdepth*channel_count/8))

Answer 2

It depends on the file type. If it's a WAV file you can locate the file's header and determine the playback duration that way. If it's a compressed format (*.mp3 etc.) you're better off sticking to the method you mentioned.

Answer 3

You can use the Audio File Services functions. There's one property to get that should give you the estimated duration. Code:

    NSURL *afUrl = [NSURL fileURLWithPath:soundPath];
    AudioFileID fileID;
    OSStatus result = AudioFileOpenURL((CFURLRef)afUrl, kAudioFileReadPermission, 0, &fileID);
    UInt64 outDataSize = 0;
    UInt32 thePropSize = sizeof(UInt64);
    result = AudioFileGetProperty(fileID, kAudioFilePropertyEstimatedDuration, &thePropSize, &outDataSize);
    AudioFileClose(fileID);

You can check the docs here

Answer 4

Hi,

I am also using kAudioFilePropertyEstimatedDuration property to get duration . but in what format it will give duration. ?? and in which parameter it will give output. ?

NSURL *afUrl = [NSURL fileURLWithPath:soundPath];
AudioFileID fileID;
OSStatus result = AudioFileOpenURL((CFURLRef)afUrl, kAudioFileReadPermission, 0, &fileID);
UInt64 outDataSize = 0;

UInt32 thePropSize = sizeof(UInt64);
result = AudioFileGetProperty(fileID, kAudioFilePropertyEstimatedDuration, &thePropSize, &outDataSize);
AudioFileClose(fileID);

I will get outDataSize for duration but it is giving big value. I want to know in which format it is giving me duration and how can I convert that into Seconds. ?

Thanks in advance