[alsa-devel] zero appl_ptr reported

[Takashi Iwai]

At Thu, 19 Feb 2009 13:20:16 +0800,
Wu Fengguang wrote:
> 
> Hi Takashi,
> 
> I noticed that 'appl_ptr' is always 0 during playback, whether it be
> mplayer or aplay, T61 or DG45ID. Is this a bug?

No, it's a feature.  When you use dmix, the appl_ptr isn't updated
in the driver side but the driver is running in a "free-wheel" mode.
OTOH, if you use pulseaudio or use HDMI out, the device is opened in a
normal mode, thus appl_ptr is handled in the driver side.


Takashi

> 
>         % grep -r . /proc/asound/card0/pcm0p
>         /proc/asound/card0/pcm0p/sub0/prealloc_max:32768
>         /proc/asound/card0/pcm0p/sub0/prealloc:64
>         /proc/asound/card0/pcm0p/sub0/status:state: RUNNING
>         /proc/asound/card0/pcm0p/sub0/status:trigger_time: 260.550520867
>         /proc/asound/card0/pcm0p/sub0/status:tstamp      : 264.361429403
>         /proc/asound/card0/pcm0p/sub0/status:delay       : -182952
>         /proc/asound/card0/pcm0p/sub0/status:avail       : 191144
>         /proc/asound/card0/pcm0p/sub0/status:avail_max   : 191144
>         /proc/asound/card0/pcm0p/sub0/status:-----
>         /proc/asound/card0/pcm0p/sub0/status:hw_ptr      : 182952
>         /proc/asound/card0/pcm0p/sub0/status:appl_ptr    : 0
>         /proc/asound/card0/pcm0p/sub0/sw_params:tstamp_mode: ENABLE
>         /proc/asound/card0/pcm0p/sub0/sw_params:period_step: 1
>         /proc/asound/card0/pcm0p/sub0/sw_params:avail_min: 1024
>         /proc/asound/card0/pcm0p/sub0/sw_params:start_threshold: 1
>         /proc/asound/card0/pcm0p/sub0/sw_params:stop_threshold: 4611686018427387904
>         /proc/asound/card0/pcm0p/sub0/sw_params:silence_threshold: 0
>         /proc/asound/card0/pcm0p/sub0/sw_params:silence_size: 4611686018427387904
>         /proc/asound/card0/pcm0p/sub0/sw_params:boundary: 4611686018427387904
>         /proc/asound/card0/pcm0p/sub0/hw_params:access: MMAP_INTERLEAVED
>         /proc/asound/card0/pcm0p/sub0/hw_params:format: S32_LE
>         /proc/asound/card0/pcm0p/sub0/hw_params:subformat: STD
>         /proc/asound/card0/pcm0p/sub0/hw_params:channels: 2
>         /proc/asound/card0/pcm0p/sub0/hw_params:rate: 48000 (48000/1)
>         /proc/asound/card0/pcm0p/sub0/hw_params:period_size: 1024
>         /proc/asound/card0/pcm0p/sub0/hw_params:buffer_size: 8192
>         /proc/asound/card0/pcm0p/sub0/info:card: 0
>         /proc/asound/card0/pcm0p/sub0/info:device: 0
>         /proc/asound/card0/pcm0p/sub0/info:subdevice: 0
>         /proc/asound/card0/pcm0p/sub0/info:stream: PLAYBACK
>         /proc/asound/card0/pcm0p/sub0/info:id: STAC92xx Analog
>         /proc/asound/card0/pcm0p/sub0/info:name: STAC92xx Analog
>         /proc/asound/card0/pcm0p/sub0/info:subname: subdevice #0
>         /proc/asound/card0/pcm0p/sub0/info:class: 0
>         /proc/asound/card0/pcm0p/sub0/info:subclass: 0
>         /proc/asound/card0/pcm0p/sub0/info:subdevices_count: 1
>         /proc/asound/card0/pcm0p/sub0/info:subdevices_avail: 0
>         /proc/asound/card0/pcm0p/xrun_debug:0
>         /proc/asound/card0/pcm0p/info:card: 0
>         /proc/asound/card0/pcm0p/info:device: 0
>         /proc/asound/card0/pcm0p/info:subdevice: 0
>         /proc/asound/card0/pcm0p/info:stream: PLAYBACK
>         /proc/asound/card0/pcm0p/info:id: STAC92xx Analog
>         /proc/asound/card0/pcm0p/info:name: STAC92xx Analog
>         /proc/asound/card0/pcm0p/info:subname: subdevice #0
>         /proc/asound/card0/pcm0p/info:class: 0
>         /proc/asound/card0/pcm0p/info:subclass: 0
>         /proc/asound/card0/pcm0p/info:subdevices_count: 1
>         /proc/asound/card0/pcm0p/info:subdevices_avail: 0
> 
> 
> Interestingly DG45ID HDMI audio playback does not have this problem:
> 
>         /proc/asound/card0/pcm3p/sub0/prealloc_max:32768
>         /proc/asound/card0/pcm3p/sub0/prealloc:64
>         /proc/asound/card0/pcm3p/sub0/status:state: RUNNING
>         /proc/asound/card0/pcm3p/sub0/status:trigger_time: 441.375970806
>         /proc/asound/card0/pcm3p/sub0/status:tstamp      : 447.039903859
>         /proc/asound/card0/pcm3p/sub0/status:delay       : 16096
>         /proc/asound/card0/pcm3p/sub0/status:avail       : 288
>         /proc/asound/card0/pcm3p/sub0/status:avail_max   : 288
>         /proc/asound/card0/pcm3p/sub0/status:-----
>         /proc/asound/card0/pcm3p/sub0/status:hw_ptr      : 249824
>         /proc/asound/card0/pcm3p/sub0/status:appl_ptr    : 265920
>         /proc/asound/card0/pcm3p/sub0/sw_params:tstamp_mode: NONE
>         /proc/asound/card0/pcm3p/sub0/sw_params:period_step: 1
>         /proc/asound/card0/pcm3p/sub0/sw_params:avail_min: 1024
>         /proc/asound/card0/pcm3p/sub0/sw_params:start_threshold: 1024
>         /proc/asound/card0/pcm3p/sub0/sw_params:stop_threshold: 4611686018427387904
>         /proc/asound/card0/pcm3p/sub0/sw_params:silence_threshold: 0
>         /proc/asound/card0/pcm3p/sub0/sw_params:silence_size: 4611686018427387904
>         /proc/asound/card0/pcm3p/sub0/sw_params:boundary: 4611686018427387904
>         /proc/asound/card0/pcm3p/sub0/hw_params:access: RW_INTERLEAVED
>         /proc/asound/card0/pcm3p/sub0/hw_params:format: S16_LE
>         /proc/asound/card0/pcm3p/sub0/hw_params:subformat: STD
>         /proc/asound/card0/pcm3p/sub0/hw_params:channels: 2
>         /proc/asound/card0/pcm3p/sub0/hw_params:rate: 44100 (44100/1)
>         /proc/asound/card0/pcm3p/sub0/hw_params:period_size: 1024
>         /proc/asound/card0/pcm3p/sub0/hw_params:buffer_size: 16384
>         /proc/asound/card0/pcm3p/sub0/info:card: 0
>         /proc/asound/card0/pcm3p/sub0/info:device: 3
>         /proc/asound/card0/pcm3p/sub0/info:subdevice: 0
>         /proc/asound/card0/pcm3p/sub0/info:stream: PLAYBACK
>         /proc/asound/card0/pcm3p/sub0/info:id: INTEL HDMI
>         /proc/asound/card0/pcm3p/sub0/info:name: INTEL HDMI
>         /proc/asound/card0/pcm3p/sub0/info:subname: subdevice #0
>         /proc/asound/card0/pcm3p/sub0/info:class: 0
>         /proc/asound/card0/pcm3p/sub0/info:subclass: 0
>         /proc/asound/card0/pcm3p/sub0/info:subdevices_count: 1
>         /proc/asound/card0/pcm3p/sub0/info:subdevices_avail: 0
>         /proc/asound/card0/pcm3p/xrun_debug:0
>         /proc/asound/card0/pcm3p/info:card: 0
>         /proc/asound/card0/pcm3p/info:device: 3
>         /proc/asound/card0/pcm3p/info:subdevice: 0
>         /proc/asound/card0/pcm3p/info:stream: PLAYBACK
>         /proc/asound/card0/pcm3p/info:id: INTEL HDMI
>         /proc/asound/card0/pcm3p/info:name: INTEL HDMI
>         /proc/asound/card0/pcm3p/info:subname: subdevice #0
>         /proc/asound/card0/pcm3p/info:class: 0
>         /proc/asound/card0/pcm3p/info:subclass: 0
>         /proc/asound/card0/pcm3p/info:subdevices_count: 1
>         /proc/asound/card0/pcm3p/info:subdevices_avail: 0
> 
> Thanks,
> Fengguang
>