snd_pcm_channel_info

Information structure for a PCM channel

Synopsis:

#include <sys/asound_common.h>

typedef struct snd_pcm_channel_info
{
    int32_t     subdevice;              
    int8_t      subname[36];            
    int32_t     channel;                
    int32_t     zero1;                  
    int32_t     output_class;           
    int32_t     output_classes;         
    int32_t     zero2[2];               
    uint32_t    flags;                  
    uint32_t    formats;                
    uint32_t    rates;                  
    int32_t     min_rate;               
    int32_t     max_rate;               
    int32_t     min_voices;             
    int32_t     max_voices;             
    int32_t     max_buffer_size;        
    int32_t     min_fragment_size;      
    int32_t     max_fragment_size;      
    int32_t     fragment_align;         
    int32_t     fifo_size;              
    int32_t     transfer_block_size;    
    uint8_t     zero3[4];               

    snd_pcm_digital_t dig_mask;         
    uint32_t          zero4;            
    int32_t           mixer_device;     
    snd_mixer_eid_t   mixer_eid;        
    snd_mixer_gid_t   mixer_gid;        
    uint8_t           reserved[128];    
}       snd_pcm_channel_info_t;

Description:

The snd_pcm_channel_info_t structure describes PCM channel information. The members include:

subdevice

The subdevice number.

subname[32]

The subdevice name.

channel

The channel direction; either SND_PCM_CHANNEL_CAPTURE or SND_PCM_CHANNEL_PLAYBACK.

zerp1

Padding of size uint32_t.

output_class

The output class that's used for DRM purposes. These are the valid values you can use:

SND_OUTPUT_CLASS_UKNOWN: The output channel is for an unknown type.
SND_OUTPUT_CLASS_SPEAKER: Indicates that the output channel is for speakers connected to the system.
SND_OUTPUT_CLASS_HEADPHONE: Indicates that the output channel is for headphones connected to the system.
SND_OUTPUT_CLASS_LINEOUT: Indicates that the output channel is for the line-out for the system.
SND_OUTPUT_CLASS_BLUETOOTH: Indicates that the output channel is for Bluetooth.
SND_OUTPUT_CLASS_TOSLINK: Indicates the output channel is for an S-Link connector.
SND_OUTPUT_CLASS_MIRACAST: Indicates that the output channel is for Miracast.
SND_NUM_OUTPUT_CLASSES: An end-of-list identifier that indicates the total number of output types recognized by this library.

output_classes

The mask of the supported output classes that are used for DRM purposes.

flags

Any combination of:

SND_PCM_CHNINFO_BLOCK — the hardware supports block mode.
SND_PCM_CHNINFO_BLOCK_TRANSFER — the hardware transfers samples by chunks (for example PCI burst transfers).
SND_PCM_CHNINFO_INTERLEAVE — the hardware accepts audio data composed of interleaved samples.
SND_PCM_CHNINFO_MMAP — the hardware supports mmap access.
SND_PCM_CHNINFO_MMAP_VALID — fragment samples are valid during transfer. This means that the fragment samples may be used when the io member from the mmap control structure snd_pcm_mmap_control_t is set (the fragment is being transferred).
SND_PCM_CHNINFO_NONINTERLEAVE — the hardware accepts audio data composed of noninterleaved samples.
SND_PCM_CHNINFO_OVERRANGE — the hardware supports ADC (capture) overrange detection.
SND_PCM_CHNINFO_PAUSE — the PCM device, underlying hardware, or both supports pausing and resuming of the audio stream (playback only).
SND_PCM_CHNINFO_RESTRICTED — the hardware supports muting of channel data.
SND_PCM_CHNINFO_ROUTING — the hardware supports redirecting the channel to a different transducer.
SND_PCM_CHNINFO_LOGGING — PCM logging is enabled on the channel.
SND_PCM_CHNINFO_PROTECTED_VOICE — the hardware supports a protected voice channel. A protected voice channel contains only voice data.

formats

The supported formats (SND_PCM_FMT_*).

rates

Hardware rates (SND_PCM_RATE_*).

min_rate

The minimum rate (in Hz).

max_rate

The maximum rate (in Hz).

min_voices

The minimum number of voices (probably always 1).

max_voices

The maximum number of voices.

max_buffer_size

The maximum buffer size, in bytes.

min_fragment_size

The minimum fragment size, in bytes.

max_fragment_size

The maximum fragment size, in bytes.

fragment_align

If this value is set, the size of the buffer fragments must be a multiple of this value, so that they are in the proper alignment.

fifo_size

The stream FIFO size, in bytes. Deprecated; don't use this member.

transfer_block_size

The bus transfer block size in bytes.

dig_mask

Not currently implemented.

mixer_device

The mixer device for this channel.

mixer_eid

A snd_mixer_eid_t structure that describes the mixer element identification for this channel.

mixer_gid

The mixer group identification for this channel; see snd_mixer_gid_t. You should use this mixer group in applications that are implementing their own volume controls.

This mixer group is guaranteed to be the lowest-level mixer group for your channel (or subchannel), as determined at the time that you call snd_ctl_pcm_channel_info(). If you call this function after the channel has been configured, and a subchannel has been allocated (i.e., after calling snd_pcm_channel_params()), this mixer group is the subchannel mixer group that's specific to the application's current subchannel.

If the rates, formats, min_rate, max_rate, min_voices, max_voices, and max_fragsize fields of snd_pcm_channel_info_t all contain zeroed data, the PCM device is currently not available for further playback or capture sessions.

Classification:

QNX Neutrino