[openbeosmediakit] format conversion
- From: Jérôme Duval <korli@xxxxxxxx>
- To: openbeosmediakit@xxxxxxxxxxxxx
- Date: Thu, 26 Feb 2004 15:38:40 +0100
Hi,
i was wondering about format conversions for supporting more output formats. I
just fell on this. I don't know if float to other formats conversions should be
inspired by this or not.
BTW should the OBOS mixer support int32 output ?
"If you want to convert from 16 to 8 bit without dither, there are two
approaches.
The first method is to simply chop off the least significant byte of the 16bit
word, leaving you with only the most significant byte (8bits). The wavestrip
application, a.o. Sounddesigner (with use dither set to of) S/Link and
SoundEdit
do this. In this way everything between the (vertical) 16-bitsample-values 0 to
128 will result in 8 bit zeros, but everything between 16-bit sample-values
-128
to 0 will go to an 8 bit -1.Even the slightest studio background noise (at say,
-90dB) during a 16 bit voice recording will result, when converting to 8 bits
with the chop method, in what seems like a random square wave below the 0 axis
with an amplitude of 1 (8bit) Qunit. The noise thus produced is very audible.
The second method is to round the least significant byte to the nearest most
significant byte value. This is what Soundhack, WaveConvert, Deck (optional)
and
BarbaBatch do. The most important difference is that everything between the 16
bit values -128 to +128 will round to an 8-bit zero, thus eliminating every
signal present in that area. (the area below-48dB or -99.6%). This way you will
loose the hiss described in the chop case. Hope this helps..."
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