Sound Blaster Live mixer / default DSP code		===========================================The EMU10K1 chips have a DSP part which can be programmed to supportvarious ways of sample processing, which is described here.(This article does not deal with the overall functionality of the EMU10K1 chips. See the manuals section for further details.)The ALSA driver programs this portion of chip by default code(can be altered later) which offers the following functionality:1) IEC958 (S/PDIF) raw PCM--------------------------This PCM device (it's the 4th PCM device (index 3!) and first subdevice(index 0) for a given card) allows to forward 48kHz, stereo, 16-bitlittle endian streams without any modifications to the digital output(coaxial or optical). The universal interface allows the creation of upto 8 raw PCM devices operating at 48kHz, 16-bit little endian. It wouldbe easy to add support for multichannel devices to the current code,but the conversion routines exist only for stereo (2-channel streams)at the time. Look to tram_poke routines in lowlevel/emu10k1/emufx.c for more details.2) Digital mixer controls-------------------------These controls are built using the DSP instructions. They offer extendedfunctionality. Only the default build-in code in the ALSA driver is describedhere. Note that the controls work as attenuators: the maximum value is the neutral position leaving the signal unchanged. Note that if the  same destination is mentioned in multiple controls, the signal is accumulated and can be wrapped (set to maximal or minimal value without checking of overflow).Explanation of used abbreviations:DAC    - digital to analog converterADC    - analog to digital converterI2S    - one-way three wire serial bus for digital sound by Philips Semiconductors         (this standard is used for connecting standalone DAC and ADC converters)LFE    - low frequency effects (subwoofer signal)AC97   - a chip containing an analog mixer, DAC and ADC convertersIEC958 - S/PDIFFX-bus - the EMU10K1 chip has an effect bus containing 16 accumulators.         Each of the synthesizer voices can feed its output to these accumulators         and the DSP microcontroller can operate with the resulting sum.name='Wave Playback Volume',index=0This control is used to attenuate samples for left and right PCM FX-busaccumulators. ALSA uses accumulators 0 and 1 for left and right PCM samples.The result samples are forwarded to the front DAC PCM slots of the AC97 codec.name='Wave Surround Playback Volume',index=0This control is used to attenuate samples for left and right PCM FX-busaccumulators. ALSA uses accumulators 0 and 1 for left and right PCM samples.The result samples are forwarded to the rear I2S DACs. These DACs operatesseparately (they are not inside the AC97 codec).name='Wave Center Playback Volume',index=0This control is used to attenuate samples for left and right PCM FX-busaccumulators. ALSA uses accumulators 0 and 1 for left and right PCM samples.The result is mixed to mono signal (single channel) and forwarded tothe ??rear?? right DAC PCM slot of the AC97 codec.name='Wave LFE Playback Volume',index=0This control is used to attenuate samples for left and right PCM FX-busaccumulators. ALSA uses accumulators 0 and 1 for left and right PCM.The result is mixed to mono signal (single channel) and forwarded tothe ??rear?? left DAC PCM slot of the AC97 codec.name='Wave Capture Volume',index=0name='Wave Capture Switch',index=0These controls are used to attenuate samples for left and right PCM FX-busaccumulator. ALSA uses accumulators 0 and 1 for left and right PCM.The result is forwarded to the ADC capture FIFO (thus to the standard capturePCM device).name='Music Playback Volume',index=0This control is used to attenuate samples for left and right MIDI FX-busaccumulators. ALSA uses accumulators 4 and 5 for left and right MIDI samples.The result samples are forwarded to the front DAC PCM slots of the AC97 codec.name='Music Capture Volume',index=0name='Music Capture Switch',index=0These controls are used to attenuate samples for left and right MIDI FX-busaccumulator. ALSA uses accumulators 4 and 5 for left and right PCM.The result is forwarded to the ADC capture FIFO (thus to the standard capturePCM device).name='Surround Playback Volume',index=0This control is used to attenuate samples for left and right rear PCM FX-busaccumulators. ALSA uses accumulators 2 and 3 for left and right rear PCM samples.The result samples are forwarded to the rear I2S DACs. These DACs operateseparately (they are not inside the AC97 codec).name='Surround Capture Volume',index=0name='Surround Capture Switch',index=0These controls are used to attenuate samples for left and right rear PCM FX-busaccumulators. ALSA uses accumulators 2 and 3 for left and right rear PCM samples.The result is forwarded to the ADC capture FIFO (thus to the standard capturePCM device).name='Center Playback Volume',index=0This control is used to attenuate sample for center PCM FX-bus accumulator.ALSA uses accumulator 6 for center PCM sample. The result sample is forwardedto the ??rear?? right DAC PCM slot of the AC97 codec.name='LFE Playback Volume',index=0This control is used to attenuate sample for center PCM FX-bus accumulator.ALSA uses accumulator 6 for center PCM sample. The result sample is forwardedto the ??rear?? left DAC PCM slot of the AC97 codec.name='AC97 Playback Volume',index=0This control is used to attenuate samples for left and right front ADC PCM slotsof the AC97 codec. The result samples are forwarded to the front DAC PCMslots of the AC97 codec.*********************************************************************************** Note: This control should be zero for the standard operations, otherwise ****** a digital loopback is activated.                                         ***********************************************************************************name='AC97 Capture Volume',index=0This control is used to attenuate samples for left and right front ADC PCM slotsof the AC97 codec. The result is forwarded to the ADC capture FIFO (thus tothe standard capture PCM device).*********************************************************************************** Note: This control should be 100 (maximal value), otherwise no analog    ****** inputs of the AC97 codec can be captured (recorded).                     ***********************************************************************************name='IEC958 TTL Playback Volume',index=0This control is used to attenuate samples from left and right IEC958 TTLdigital inputs (usually used by a CDROM drive). The result samples areforwarded to the front DAC PCM slots of the AC97 codec.name='IEC958 TTL Capture Volume',index=0This control is used to attenuate samples from left and right IEC958 TTLdigital inputs (usually used by a CDROM drive). The result samples areforwarded to the ADC capture FIFO (thus to the standard capture PCM device).name='Zoom Video Playback Volume',index=0This control is used to attenuate samples from left and right zoom videodigital inputs (usually used by a CDROM drive). The result samples areforwarded to the front DAC PCM slots of the AC97 codec.name='Zoom Video Capture Volume',index=0This control is used to attenuate samples from left and right zoom videodigital inputs (usually used by a CDROM drive). The result samples areforwarded to the ADC capture FIFO (thus to the standard capture PCM device).name='IEC958 LiveDrive Playback Volume',index=0This control is used to attenuate samples from left and right IEC958 opticaldigital input. The result samples are forwarded to the front DAC PCM slotsof the AC97 codec.name='IEC958 LiveDrive Capture Volume',index=0This control is used to attenuate samples from left and right IEC958 opticaldigital inputs. The result samples are forwarded to the ADC capture FIFO(thus to the standard capture PCM device).name='IEC958 Coaxial Playback Volume',index=0This control is used to attenuate samples from left and right IEC958 coaxialdigital inputs. The result samples are forwarded to the front DAC PCM slotsof the AC97 codec.name='IEC958 Coaxial Capture Volume',index=0This control is used to attenuate samples from left and right IEC958 coaxialdigital inputs. The result samples are forwarded to the ADC capture FIFO(thus to the standard capture PCM device).name='Line LiveDrive Playback Volume',index=0name='Line LiveDrive Playback Volume',index=1This control is used to attenuate samples from left and right I2S ADCinputs (on the LiveDrive). The result samples are forwarded to the frontDAC PCM slots of the AC97 codec.name='Line LiveDrive Capture Volume',index=1name='Line LiveDrive Capture Volume',index=1This control is used to attenuate samples from left and right I2S ADCinputs (on the LiveDrive). The result samples are forwarded to the ADCcapture FIFO (thus to the standard capture PCM device).name='Tone Control - Switch',index=0This control turns the tone control on or off. The samples for front, rearand center / LFE outputs are affected.name='Tone Control - Bass',index=0This control sets the bass intensity. There is no neutral value!!When the tone control code is activated, the samples are always modified.The closest value to pure signal is 20.name='Tone Control - Treble',index=0This control sets the treble intensity. There is no neutral value!!When the tone control code is activated, the samples are always modified.The closest value to pure signal is 20.name='IEC958 Optical Raw Playback Switch',index=0If this switch is on, then the samples for the IEC958 (S/PDIF) digitaloutput are taken only from the raw FX8010 PCM, otherwise standard frontPCM samples are taken.name='Headphone Playback Volume',index=1This control attenuates the samples for the headphone output.name='Headphone Center Playback Switch',index=1If this switch is on, then the sample for the center PCM is put to theleft headphone output (useful for SB Live cards without separate center/LFEoutput).name='Headphone LFE Playback Switch',index=1If this switch is on, then the sample for the center PCM is put to theright headphone output (useful for SB Live cards without separate center/LFEoutput).3) PCM stream related controls------------------------------name='EMU10K1 PCM Volume',index 0-31Channel volume attenuation in range 0-0xffff. The maximum value (noattenuation) is default. The channel mapping for three values isas follows:	0 - mono, default 0xffff (no attenuation)	1 - left, default 0xffff (no attenuation)	2 - right, default 0xffff (no attenuation)name='EMU10K1 PCM Send Routing',index 0-31This control specifies the destination - FX-bus accumulators. There aretwelve values with this mapping:	 0 -  mono, A destination (FX-bus 0-15), default 0	 1 -  mono, B destination (FX-bus 0-15), default 1	 2 -  mono, C destination (FX-bus 0-15), default 2	 3 -  mono, D destination (FX-bus 0-15), default 3	 4 -  left, A destination (FX-bus 0-15), default 0	 5 -  left, B destination (FX-bus 0-15), default 1	 6 -  left, C destination (FX-bus 0-15), default 2	 7 -  left, D destination (FX-bus 0-15), default 3	 8 - right, A destination (FX-bus 0-15), default 0	 9 - right, B destination (FX-bus 0-15), default 1	10 - right, C destination (FX-bus 0-15), default 2	11 - right, D destination (FX-bus 0-15), default 3Don't forget that it's illegal to assign a channel to the same FX-bus accumulator more than once (it means 0=0 && 1=0 is an invalid combination). name='EMU10K1 PCM Send Volume',index 0-31It specifies the attenuation (amount) for given destination in range 0-255.The channel mapping is following:	 0 -  mono, A destination attn, default 255 (no attenuation)	 1 -  mono, B destination attn, default 255 (no attenuation)	 2 -  mono, C destination attn, default 0 (mute)	 3 -  mono, D destination attn, default 0 (mute)	 4 -  left, A destination attn, default 255 (no attenuation)	 5 -  left, B destination attn, default 0 (mute)	 6 -  left, C destination attn, default 0 (mute)	 7 -  left, D destination attn, default 0 (mute)	 8 - right, A destination attn, default 0 (mute)	 9 - right, B destination attn, default 255 (no attenuation)	10 - right, C destination attn, default 0 (mute)	11 - right, D destination attn, default 0 (mute)4) MANUALS/PATENTS:-------------------ftp://opensource.creative.com/pub/doc-------------------------------------        Files:        LM4545.pdf      AC97 Codec        m2049.pdf       The EMU10K1 Digital Audio Processor        hog63.ps        FX8010 - A DSP Chip Architecture for Audio EffectsWIPO Patents------------        Patent numbers:        WO 9901813 (A1) Audio Effects Processor with multiple asynchronous (Jan. 14, 1999)                        streams        WO 9901814 (A1) Processor with Instruction Set for Audio Effects (Jan. 14, 1999)        WO 9901953 (A1) Audio Effects Processor having Decoupled Instruction                        Execution and Audio Data Sequencing (Jan. 14, 1999)US Patents (http://www.uspto.gov/)----------------------------------        US 5925841      Digital Sampling Instrument employing cache memory (Jul. 20, 1999)        US 5928342      Audio Effects Processor integrated on a single chip (Jul. 27, 1999)                        with a multiport memory onto which multiple asynchronous                        digital sound samples can be concurrently loaded        US 5930158      Processor with Instruction Set for Audio Effects (Jul. 27, 1999)        US 6032235      Memory initialization circuit (Tram) (Feb. 29, 2000)        US 6138207      Interpolation looping of audio samples in cache connected to    (Oct. 24, 2000)                        system bus with prioritization and modification of bus transfers                        in accordance with loop ends and minimum block sizes        US 6151670      Method for conserving memory storage using a (Nov. 21, 2000)                        pool of  short term memory registers        US 6195715      Interrupt control for multiple programs communicating with      (Feb. 27, 2001)                        a common interrupt by associating programs to GP registers,                        defining interrupt register, polling GP registers, and invoking                        callback routine associated with defined interrupt register