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02-18-2008, 09:34 AM
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 Re: 8kHz sampling rates and i2s based ppc audio devices On Fri, Nov 23, 2007 at 05:50:27PM +0100, Marco Trillo wrote: > Hi, > > At 2007-11-22 21:48:40, Jacob Meuser wrote: > > It's been reported that 8kHz sampling rates cause an "evil" > > sound with snapper(4). 8kHz is the audio(4) default, so, just > > about any operation with these devices causes the "evil" sound. > > I have experienced that too with snapper(4). I also recall that some > users mentioned audio stability problems after playing a lot of files with > tumbler(4), this may be the cause of such problems (if they were using > the /dev/audio device with its 8 kHz default rate). > > > disabling 8kHz in sys/arch/macppc/dev/i2s.c avoids the "evil" sound. > > however, this disables 8kHz sampling rates in all i2s based audio > > devices, and I'd rather not do that if not necessary. > > According to the datasheets of these codecs, these are the supported rates: > snapper: 32 kHz, 44.1 kHz, 48 kHz > tumbler: 32 kHz, 44.1 kHz, 48 kHz, 96 kHz > daca: 8 kHz, 11.025 kHz, 12 kHz, 16 kHz, 22.05 kHz, 24 kHz, 32 kHz, > 44.1 kHz, 48 kHz > > 'snapper' and 'tumbler' do not require any special configuration to set the > sampling rate. However, 'daca' might need to be informed of the band of the > rate setting via the I2C register SR_REG (subaddress 0x01). These are > the values: > > 000 32-48 kHz > 001 26-32 kHz > 010 20-26 kHz > 011 14-20 kHz > 100 10-14 kHz > 101 8-10 kHz > > The current daca(4) driver does not configure this register, and the > default setting > is the 32-48 kHz band. > There is also an autoselect mode, but this appears to be for MPEG streams. thanks. the information is much appreciated. -- jakemsr@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org      |
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