363 lines
9.2 KiB
Plaintext
363 lines
9.2 KiB
Plaintext
Software Interface ALSA-DSP MADI Driver
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(translated from German, so no good English ;-),
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2004 - winfried ritsch
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Full functionality has been added to the driver. Since some of
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the Controls and startup-options are ALSA-Standard and only the
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special Controls are described and discussed below.
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hardware functionality:
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Audio transmission:
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number of channels -- depends on transmission mode
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The number of channels chosen is from 1..Nmax. The reason to
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use for a lower number of channels is only resource allocation,
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since unused DMA channels are disabled and less memory is
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allocated. So also the throughput of the PCI system can be
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scaled. (Only important for low performance boards).
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Single Speed -- 1..64 channels
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(Note: Choosing the 56channel mode for transmission or as
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receiver, only 56 are transmitted/received over the MADI, but
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all 64 channels are available for the mixer, so channel count
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for the driver)
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Double Speed -- 1..32 channels
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Note: Choosing the 56-channel mode for
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transmission/receive-mode , only 28 are transmitted/received
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over the MADI, but all 32 channels are available for the mixer,
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so channel count for the driver
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Quad Speed -- 1..16 channels
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Note: Choosing the 56-channel mode for
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transmission/receive-mode , only 14 are transmitted/received
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over the MADI, but all 16 channels are available for the mixer,
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so channel count for the driver
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Format -- signed 32 Bit Little Endian (SNDRV_PCM_FMTBIT_S32_LE)
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Sample Rates --
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Single Speed -- 32000, 44100, 48000
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Double Speed -- 64000, 88200, 96000 (untested)
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Quad Speed -- 128000, 176400, 192000 (untested)
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access-mode -- MMAP (memory mapped), Not interleaved
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(PCM_NON-INTERLEAVED)
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buffer-sizes -- 64,128,256,512,1024,2048,8192 Samples
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fragments -- 2
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Hardware-pointer -- 2 Modi
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The Card supports the readout of the actual Buffer-pointer,
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where DMA reads/writes. Since of the bulk mode of PCI it is only
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64 Byte accurate. SO it is not really usable for the
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ALSA-mid-level functions (here the buffer-ID gives a better
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result), but if MMAP is used by the application. Therefore it
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can be configured at load-time with the parameter
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precise-pointer.
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(Hint: Experimenting I found that the pointer is maximum 64 to
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large never to small. So if you subtract 64 you always have a
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safe pointer for writing, which is used on this mode inside
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ALSA. In theory now you can get now a latency as low as 16
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Samples, which is a quarter of the interrupt possibilities.)
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Precise Pointer -- off
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interrupt used for pointer-calculation
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Precise Pointer -- on
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hardware pointer used.
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Controller:
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Since DSP-MADI-Mixer has 8152 Fader, it does not make sense to
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use the standard mixer-controls, since this would break most of
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(especially graphic) ALSA-Mixer GUIs. So Mixer control has be
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provided by a 2-dimensional controller using the
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hwdep-interface.
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Also all 128+256 Peak and RMS-Meter can be accessed via the
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hwdep-interface. Since it could be a performance problem always
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copying and converting Peak and RMS-Levels even if you just need
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one, I decided to export the hardware structure, so that of
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needed some driver-guru can implement a memory-mapping of mixer
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or peak-meters over ioctl, or also to do only copying and no
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conversion. A test-application shows the usage of the controller.
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Latency Controls --- not implemented !!!
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Note: Within the windows-driver the latency is accessible of a
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control-panel, but buffer-sizes are controlled with ALSA from
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hwparams-calls and should not be changed in run-state, I did not
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implement it here.
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System Clock -- suspended !!!!
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Name -- "System Clock Mode"
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Access -- Read Write
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Values -- "Master" "Slave"
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!!!! This is a hardware-function but is in conflict with the
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Clock-source controller, which is a kind of ALSA-standard. I
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makes sense to set the card to a special mode (master at some
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frequency or slave), since even not using an Audio-application
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a studio should have working synchronisations setup. So use
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Clock-source-controller instead !!!!
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Clock Source
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Name -- "Sample Clock Source"
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Access -- Read Write
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Values -- "AutoSync", "Internal 32.0 kHz", "Internal 44.1 kHz",
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"Internal 48.0 kHz", "Internal 64.0 kHz", "Internal 88.2 kHz",
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"Internal 96.0 kHz"
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Choose between Master at a specific Frequency and so also the
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Speed-mode or Slave (Autosync). Also see "Preferred Sync Ref"
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!!!! This is no pure hardware function but was implemented by
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ALSA by some ALSA-drivers before, so I use it also. !!!
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Preferred Sync Ref
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Name -- "Preferred Sync Reference"
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Access -- Read Write
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Values -- "Word" "MADI"
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Within the Auto-sync-Mode the preferred Sync Source can be
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chosen. If it is not available another is used if possible.
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Note: Since MADI has a much higher bit-rate than word-clock, the
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card should synchronise better in MADI Mode. But since the
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RME-PLL is very good, there are almost no problems with
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word-clock too. I never found a difference.
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TX 64 channel ---
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Name -- "TX 64 channels mode"
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Access -- Read Write
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Values -- 0 1
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Using 64-channel-modus (1) or 56-channel-modus for
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MADI-transmission (0).
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Note: This control is for output only. Input-mode is detected
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automatically from hardware sending MADI.
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Clear TMS ---
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Name -- "Clear Track Marker"
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Access -- Read Write
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Values -- 0 1
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Don't use to lower 5 Audio-bits on AES as additional Bits.
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Safe Mode oder Auto Input ---
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Name -- "Safe Mode"
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Access -- Read Write
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Values -- 0 1
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(default on)
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If on (1), then if either the optical or coaxial connection
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has a failure, there is a takeover to the working one, with no
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sample failure. Its only useful if you use the second as a
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backup connection.
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Input ---
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Name -- "Input Select"
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Access -- Read Write
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Values -- optical coaxial
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Choosing the Input, optical or coaxial. If Safe-mode is active,
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this is the preferred Input.
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-------------- Mixer ----------------------
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Mixer
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Name -- "Mixer"
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Access -- Read Write
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Values - <channel-number 0-127> <Value 0-65535>
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Here as a first value the channel-index is taken to get/set the
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corresponding mixer channel, where 0-63 are the input to output
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fader and 64-127 the playback to outputs fader. Value 0
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is channel muted 0 and 32768 an amplification of 1.
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Chn 1-64
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fast mixer for the ALSA-mixer utils. The diagonal of the
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mixer-matrix is implemented from playback to output.
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Line Out
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Name -- "Line Out"
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Access -- Read Write
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Values -- 0 1
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Switching on and off the analog out, which has nothing to do
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with mixing or routing. the analog outs reflects channel 63,64.
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--- information (only read access):
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Sample Rate
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Name -- "System Sample Rate"
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Access -- Read-only
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getting the sample rate.
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External Rate measured
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Name -- "External Rate"
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Access -- Read only
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Should be "Autosync Rate", but Name used is
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ALSA-Scheme. External Sample frequency liked used on Autosync is
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reported.
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MADI Sync Status
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Name -- "MADI Sync Lock Status"
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Access -- Read
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Values -- 0,1,2
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MADI-Input is 0=Unlocked, 1=Locked, or 2=Synced.
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Word Clock Sync Status
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Name -- "Word Clock Lock Status"
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Access -- Read
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Values -- 0,1,2
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Word Clock Input is 0=Unlocked, 1=Locked, or 2=Synced.
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AutoSync
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Name -- "AutoSync Reference"
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Access -- Read
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Values -- "WordClock", "MADI", "None"
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Sync-Reference is either "WordClock", "MADI" or none.
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RX 64ch --- noch nicht implementiert
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MADI-Receiver is in 64 channel mode oder 56 channel mode.
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AB_inp --- not tested
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Used input for Auto-Input.
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actual Buffer Position --- not implemented
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!!! this is a ALSA internal function, so no control is used !!!
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Calling Parameter:
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index int array (min = 1, max = 8),
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"Index value for RME HDSPM interface." card-index within ALSA
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note: ALSA-standard
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id string array (min = 1, max = 8),
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"ID string for RME HDSPM interface."
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note: ALSA-standard
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enable int array (min = 1, max = 8),
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"Enable/disable specific HDSPM sound-cards."
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note: ALSA-standard
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precise_ptr int array (min = 1, max = 8),
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"Enable precise pointer, or disable."
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note: Use only when the application supports this (which is a special case).
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line_outs_monitor int array (min = 1, max = 8),
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"Send playback streams to analog outs by default."
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note: each playback channel is mixed to the same numbered output
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channel (routed). This is against the ALSA-convention, where all
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channels have to be muted on after loading the driver, but was
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used before on other cards, so i historically use it again)
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enable_monitor int array (min = 1, max = 8),
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"Enable Analog Out on Channel 63/64 by default."
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note: here the analog output is enabled (but not routed).
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