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axfer: fulfill manual section for libasound backend
This commit attempts to describe purpose of each option with more texts than aplay(1). I note that a section for scheduling model will be prepared near future. This commit just adds a placeholder for the section. Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de>
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Takashi Sakamoto
Takashi Iwai
parent
a0fb855e35
commit
0edb6ec765
1 changed files with 255 additions and 1 deletions
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@ -241,7 +241,257 @@ Select backend of transmission from a list below. The default is libasound.
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.SS Backend options for libasound
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(placeholder)
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.TP
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.B \-D, \-\-device
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This option is used to select PCM node in libasound configuration space.
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Available nodes are listed by
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.I pcm
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operation of
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.I list
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subcommand.
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.TP
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.B \-N, \-\-nonblock
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With this option, PCM substream is opened in non\-blocking mode. When audio
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data frame is not available in buffer of the PCM substream, I/O operation
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immediately returns without blocking process. This option implicitly uses
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.I \-\-waiter\-type
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option as well to prevent heavy consumption of CPU time.
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.TP
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.B \-M, \-\-mmap
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With this option, audio data frame is processed directly in buffer of PCM
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substream if selected node supports this operation. Without the option,
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temporary buffers are used to copy audio data frame for buffer of PCM substream.
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This option implicitly uses
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.I \-\-waiter\-type
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option as well to prevent heavy consumption of CPU time.
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.TP
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.B \-F, \-\-period\-size
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This option configures given value to
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.I period_size
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hardware parameter of PCM substream. The parameter indicates the number of audio
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data frame per period in buffer of the PCM substream. Actual number is decided
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as a result of interaction between each implementation of PCM plugin chained
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from the selected PCM node, and in\-kernel driver or PCM I/O plugins.
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Ideally, the same amount of audio data frame as the value should be handled in
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one I/O operation. Actually, it is not, depending on implementation of the PCM
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plugins, in\-kernel driver, PCM I/O plugins and scheduling model. For \(aqhw\(aq
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PCM plugin in \(aqirq\(aq scheduling model, the value is used to decide
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intervals of hardware interrupt, thus the same amount of audio data frame as
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the value is expected to be available for one I/O operation.
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.TP
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.B \-\-period\-time
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This option configures given value to
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.I period_time
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hardware parameter of PCM substream. This option is similar to
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.I \-\-period\-size
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option, however its unit is micro\-second.
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.TP
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.B \-B, \-\-buffer\-size
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This option configures given value to
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.I buffer_size
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hardware parameter of PCM substream. The parameter indicates the number of audio
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data frame in buffer of PCM substream. Actual number is decided as a result of
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interaction between each implementation of PCM plugin chained from the selected
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PCM node, and in\-kernel driver or PCM I/O plugins.
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Ideally, this is multiples of the number of audio data frame per period, thus
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the size of period. Actually, it is not, depending on implementation of the PCM
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plugins, in\-kernel driver and PCM I/O plugins.
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.TP
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.B \-\-buffer\-time
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This option configures given value to
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.I buffer_time
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hardware parameter of PCM substream. This option is similar to
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.I \-\-buffer\-size
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option, however its unit is micro\-second.
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.TP
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.B \-\-waiter\-type
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This option indicates the type of waiter for event notification. At present,
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four types are available;
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.I default
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,
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.I select
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,
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.I poll
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and
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.I epoll
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\&. With
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.I default
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type, \(aqsnd_pcm_wait()\(aq is used. With
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.I select
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type, \(aqselect(2)\(aq system call is used. With
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.I poll
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type, \(aqpoll(2)\(aq system call is used. With
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.I epoll
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type, Linux\-specific \(aqepoll(7)\(aq system call is used.
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This option should correspond to one of
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.I \-\-nonblock
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or
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.I \-\-mmap
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options, or
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.I timer
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value of
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.I \-\-sched\-model
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option.
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Neither this option nor
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.I \-\-test\-nowait
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is available at the same time.
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.TP
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.B \-\-sched\-model
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This option selects scheduling model for process of this program. One of
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.I irq
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or
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.I timer
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is available. In detail, please read \(aqSCHEDULING MODEL\(aq section.
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When nothing specified,
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.I irq
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model is used.
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.TP
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.B \-A, \-\-avail\-min
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This option configures given value to
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.I avail\-min
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software parameter of PCM substream. In blocking mode, the value is used as
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threshold of the number of available audio data frames in buffer of PCM
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substream to wake up process blocked by I/O operation. In non\-blocking mode,
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any I/O operation returns \-EAGAIN untill the available number of audio data frame reaches the threshold.
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This option has an effect in cases neither
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.I \-\-mmap
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nor
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.I timer
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value of
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.I \-\-sched\-model
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option is used.
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.TP
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.B \-R, \-\-start\-delay
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This option configures given value to
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.I start_threshold
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software parameter of PCM substream. The value is used as threshold to start
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PCM substream automatically. At present, this option has an effect in cases
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neither
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.I \-\-mmap
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nor
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.I timer
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value of
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.I \-\-sched\-model
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option is used.
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For playback transmission, when the number of accumulated audio data frame
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in buffer of PCM substream to which this program writes out reaches the
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threshold, the PCM substream starts automatically without an explicit call of
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.I snd_pcm_start()
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to the PCM substream.
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For capture transmission, this option is useless. The number of
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accumulated audio data frame is not increased without an explicit call of
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.I snd_pcm_start()
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to the PCM substream.
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This option has an effect in cases neither
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.I \-\-mmap
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nor
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.I timer
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value of
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.I \-\-sched\-model
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option is used.
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.TP
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.B \-T, \-\-stop\-delay
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This option configures given value to
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.I stop_threshold
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software parameter of PCM substream. The value is used as threshold to stop PCM
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substream automatically. At present, this option has an effect in cases neither
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.I \-\-mmap
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nor
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.I timer
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value of
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.I \-\-sched\-model
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option is used.
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For capture transmission, when the number of accumulated audio data frame
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in buffer of PCM substream to which a driver or alsa\-lib PCM plugins write
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reaches the threshold, the PCM substream stops automatically without an explicit
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call of
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.I snd_pcm_stop()
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to the PCM substream. This is a case that this program leaves the audio data
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frames without reading for a while.
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For playback transmission, when the number available audio data frame in buffer
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of PCM substream from which a driver or alsa\-lib PCM plugins read reaches the
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threshold, the PCM substream stops automatically without an explicit call of
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.I snd_pcm_stop()
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to the PCM substream. This is a case that this program leaves the audio data
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frames without writing for a while.
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This option has an effect in cases neither
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.I \-\-mmap
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nor
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.I timer
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value of
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.I \-\-sched\-model
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option is used.
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.TP
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.B \-\-disable\-resample
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This option has an effect for \(aqplug\(aq plugin in alsa\-lib to suppress
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conversion of sampling rate for audio data frame.
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.TP
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.B \-\-disable\-channels
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This option has an effect for \(aqplug\(aq plugin in alsa\-lib to suppress
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conversion of channels for audio data frame.
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.TP
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.B \-\-disable\-format
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This option has an effect for \(aqplug\(aq plugin in alsa\-lib to suppress
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conversion of sample format for audio data frame.
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.TP
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.B \-\-disable\-softvol
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This option has an effect for \(aqsoftvol\(aq plugin in alsa\-lib to suppress
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conversion of samples for audio data frame via additional control element.
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.TP
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.B \-\-fatal\-errors
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This option suppresses recovery operation from XRUN state of running PCM
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substream, then process of this program is going to finish as usual.
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.TP
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.B \-\-test\-nowait
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This option disables any waiter for I/O event notification. I/O operations are
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iterated till any of audio data frame is available. The option brings heavy
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load in consumption of CPU time.
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.SS Backend options for libffado
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@ -413,6 +663,10 @@ The above will transfer audio data frame as sample format of 48.0 kHz, 2
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channels, signed 32 bit big endian PCM for 1,024 number of data frames to files
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named \(aqchannels\-1.au\(aq and \(aqchannels\-2.au\(aq.
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.SH SCHEDULING MODEL
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(placeholder)
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.SH COMPATIBILITY TO APLAY
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The
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