Re: FLLR (compression ?) in AIFF file
Re: FLLR (compression ?) in AIFF file
- Subject: Re: FLLR (compression ?) in AIFF file
- From: Brian Willoughby <email@hidden>
- Date: Wed, 6 Aug 2008 12:58:49 -0700
If you're having trouble reading AIFF with your own code, then
perhaps you should use the Apple AudioFIle and ExtAudioFile API. A
proper file parsing API should help a great deal, and Apple's will
translate from 16-bit fixed to 32-bit float for you. There may be
3rd-party AIFF libraries, too.
By the way, AIFF never stores float. AIFC can store float, but only
with certain compression types.
Brian Willoughby
Sound Consulting
On Aug 6, 2008, at 12:28, Francois Baronnet wrote:
Ok, thanks. As I'm the recorder of the sound and then there is
only me
to analyse it (then the sound file is deleted), I thing I can use
uncompressed AIFF, no?
Please correct me if I go wrong, but if I move to the SSND chunk, I
should find very closed to it the "sound data", shouldn't I?
And these data must be of type float, from -1.000 to 1.000, right? If
it's true, then I don't understand why I'm getting stange numbers
(xxx.xx E-41 for example).
Here is a screenshot of my file opened with some hexadecimal editor.
My app is reading from 00 22 00 00 until the end of file.
http://cpcstats.free.fr/upload/files/1218044603_Image_1.png
May be it's not float? May be the offset isn't good? I tried many
combinations but I can't get one "good" float value...
Oooops...
Now I'm reading my data (16 bit float) 2 bytes by 2 bytes (first 30
000) and I'm getting all values between -1.999 and -1.991.
float value;
int i=0;
do
{
[[theFileHandle readDataOfLength: 2] getBytes: &value];
NSLog(@"%f",value);
chunkSize -= 2;
i++;
}while(chunkSize > 0 && i < 30000);
I haven't plot my values but I'm pretty sure it won't look like a nice
wave as I can see in Audacity...
--
François Baronnet
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