On 2023-07-04 12:00, Alexandre Ratchov wrote:
On Mon, Jul 03, 2023 at 05:18:13PM -0400, Ricky Cintron wrote:
While troubleshooting some audio issues, I noticed that the values of
play.bytes and record.bytes in audioctl's output were identical, even
when only playing audio.
1) Is this expected behavior?
yes, by default the device always does DMA in both directions
(synchronously), so record.bytes increases like play.bytes
Great to know! This, along with the other details you've provided, will
help me understand what I'm seeing much more clearly now.
Thank you.
2) What is the source of this data (record.bytes)?
The source is the audio hardware interrupts. The audio(4) driver
handles them and increments its couter. The counter is readable by
userland with the AUDIO_GETPOS ioctl.
I found it interesting that the values were the same, so I took a look
at mixerctl, and noticed that 'line' (which is an output) and 'mix'
(which has line as its only source) were the sources for both
record.adc variables. At that point I figured that simply removing
all sources from those two variables would eliminate all audio data
from those recording channels, but record.bytes continued to match
play.bytes. I even attempted to mute both ADCs and to disable
recording
in mixerctl (without rebooting), but nothing changed.
I'm probably going to remove 'line' and 'mix' as sources for the ADCs
because they don't make sense there, but I'm still hoping to
understand
what's going on.
The mixer is a completely different thing and is completely
independent from DMA. It is supposed to control the analog
knobs/selectors, jack sensors, and alike.
Setting the record level to 0 (or removing all sources) would make the
ADC sample silence and produce zeros without affecting how it
works. That's why record.bytes still increases.
# mixerctl -v
inputs.dac-2:3=126,126
inputs.dac-0:1=126,126
record.adc-0:1_mute=off [ off on ]
record.adc-0:1=124,124
record.adc-2:3_mute=off [ off on ]
record.adc-2:3=124,124
inputs.mix_source=line { line }
inputs.mix_line=120,120
inputs.mix2_source=dac-2:3 { dac-2:3 mix }
inputs.mix3_source=dac-0:1 { dac-0:1 mix }
outputs.spkr_source=mix2 [ mix2 ]
outputs.spkr_mute=on [ off on ]
outputs.spkr_eapd=on [ off on ]
outputs.line_source=mix3 [ mix2 mix3 ]
outputs.line_mute=off [ off on ]
inputs.line=85,85
outputs.line_dir=output [ none output input input-vr0 input-vr50
input-vr80
input-vr100 ]
outputs.line_boost=off [ off on ]
outputs.line_eapd=on [ off on ]
outputs.hp_source=mix2 [ mix2 mix3 ]
outputs.hp_mute=off [ off on ]
outputs.hp_boost=off [ off on ]
outputs.hp_eapd=on [ off on ]
record.adc-2:3_source=line,mix { line mix }
record.adc-0:1_source=line,mix { line mix }
outputs.line_sense=plugged [ unplugged plugged ]
outputs.hp_sense=unplugged [ unplugged plugged ]
outputs.spkr_muters=line,hp { line hp }
outputs.master=126,126
outputs.master.mute=off [ off on ]
outputs.master.slaves=dac-2:3,dac-0:1,spkr,line,hp { dac-2:3 dac-0:1
spkr
line hp }
record.volume=124,124
record.volume.mute=off [ off on ]
record.volume.slaves=adc-0:1,adc-2:3 { adc-0:1 adc-2:3 line }
record.enable=sysctl [ off on sysctl ]
