Re: kAudioFormatFlagIsFloat sample range
Re: kAudioFormatFlagIsFloat sample range
- Subject: Re: kAudioFormatFlagIsFloat sample range
- From: Paul Davis <email@hidden>
- Date: Sun, 12 Sep 2010 15:43:02 -0400
On Sun, Sep 12, 2010 at 3:01 AM, Brian Willoughby <email@hidden> wrote:
> As for AAC, it's a complex sum of multiple frequency bands, so it seems
> easily possible that the reconstructed wave might exceed the normal range.
> For sure, the waveform out of AAC is not going to match the waveform that
> went in, so it could just as easily be higher amplitude as lower amplitude.
> I would assume that the frequency banks in the AAC reconstruction filters
> have weights that would never sum to more than 1.0 in amplitude, but I must
> admit that I have not studied lossy formats because I primarily use
> lossless.
just for reference, we have seen the kind of issue brian describes
above using libsndfile (and libogg) to decode ogg/vorbis files, and
had to introduce some special case code in ardour/mixbus to avoid the
resulting signal from appearing to be clipped after being imported.
this is also a non-definitive answer, but might be helpful in
confirming that this is not necessarily a totally unusual phenomena.
--p
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