IMA 4:1 Compression woes

Posted: Thu Sep 06, 2001 12:33 pm

HowdyI recently finished a score for a
computer game and checked out a late FC (Final Conadidate) version. In this version, I noticed that the music exhibited more than a subtle amount of what sounds like quantization noise. You can listen to the files here.The source for both files is a 44k, 16 bit .wav recorded to Sound Forge 5 from an O2r. The "bad" file was compressed (for the purposes of this example) using the "IMA ADPCM" format in SF5. Although I'm not certain this is the same as the "IMA 4:1" compression option I used in Peak, the resulting noise is similar.Through the rest of the game, loud sources are less affected by this noise than quiet ones. Must one squeeze the dynamic range to avoid this kind of noise? Should one pre-filter highs and lows for optimal sound? My previous experience with this compression and the resulting sound was good. I'm just trying to determine why now, especially on the piano that the audio sounds like "ass".And, unfortunately (of course) its too late to update the audio for the game. The upside is, through horrid "multimedia" speakers, the noise is all but inaudible.Thanks

Posted: Thu Sep 06, 2001 5:33 pm

Hello!Sometimes a codec will "phase" causing a sound like Flutter coming through. 4:1 should not do this. I would take the piano file and for the heck of it, invert the phase 180 and try it.If you do not have a phase plug-in, you can get one here.Look for PhasePiano's have wierd phase character so this may not help you much but it is worth a try.Could you compress the track at 192KBS in MP3?Hope this helps some..

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