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Better Documentation

lleibovici

I have the board working and I'm very happy with the performance.

However I'm struggling with the documentation. I am unfamiliar with ALSA and am struggling to understand the "Use Case" scripts.

Just trying to work out how to change the volume on the headset while it is running has so far failed me. All I seem able to do is mute the channel.

Can you give us some guidance on how to identify what names to use in an amixer command for example.

What are HPOUT1L and HPOUT2L for example?

What is the difference between "Digital Volume" and "Volume"? What are the value ranges for these commands?

 

Is there some good reading available on an "Idiots guide to ALSA"?

 

Is this the right place to ask these questions?

 

Leo

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  • 0

    I think I can help a little. Although this is the halt leading the blind I think.

     

    I am able to change the volume on Line Out (which is where my speakers are plugged) which is HPOUT2. Headset, I believe is HPOUT1 so you can adapt this as needed.

     

    I wrote a zsh function. I suspect a similar thing is available for bash if that's your pleasure.

     

    #!/bin/zsh

     

    function vol() {

     

    defvol=90

        if [[ -n $1 ]] {

            vol=$1

        } else {

            vol=$defvol

        }

     

        (( ivol = $vol * 20 / 90 ))

        print "Setting volume to: $vol/$ivol"

     

        CARD="hw:0"

        BEQUIET=" -q "

        BEQUIET=""

     

    # Route LineIn input to HPOUT2s.

     

     

    # Set volume on HPOUT2s to a sane level.

    #amixer ${BEQUIET} -D${CARD} cset name='HPOUT2 Digital Volume' 128

        amixer ${BEQUIET} -D${CARD} cset name='HPOUT2 Digital Volume' $vol

        amixer ${BEQUIET} -D${CARD} cset name='HPOUT2L Input 1 Volume' $ivol

        amixer ${BEQUIET} -D${CARD} cset name='HPOUT2R Input 1 Volume' $ivol

    }

     

     

    I scaled the input volume against the 90 that was in the original Listen script. I have since learned the limits on these numbers:

     

    `--> vol 135

    Setting volume to: 135/30

    numid=156,iface=MIXER,name='HPOUT2 Digital Volume'

      ; type=INTEGER,access=rw---R--,values=2,min=0,max=191,step=0

      : values=135,135

      | dBscale-min=-64.00dB,step=0.50dB,mute=0

    numid=120,iface=MIXER,name='HPOUT2L Input 1 Volume'

      ; type=INTEGER,access=rw---R--,values=1,min=0,max=48,step=0

      : values=30

      | dBscale-min=-32.00dB,step=1.00dB,mute=0

    numid=124,iface=MIXER,name='HPOUT2R Input 1 Volume'

      ; type=INTEGER,access=rw---R--,values=1,min=0,max=48,step=0

      : values=30

      | dBscale-min=-32.00dB,step=1.00dB,mute=0

     

     

    So the scaling could/should be done better.

     

    I would like to know what the difference is between Digital Volume and Input n Volume and why the scripts set the both. I have experimented with just setting Digital Volume and that seems to control the result correctly.  Hmmm, I just noticed that Digital Volume carries 2 values. Can I assume that these are Left and Right channels??

     

    Maybe I'll just set the Input Volume to the midpoint and adjust the Digital Volume. I could make it in a range of, say, 0 to 11 then I could have an amp that GOES TO 11! ...sorry... geek reference

  • 0 in reply to ctgreybeard

    The difference between "Volume" and "Digital Volume"?

    All interfaces that have inputs have four inputs. In the Farnell/Wolfson supplied scripts only Input 1 is ever used.

    But, you can use all four to mix several different sources together.

    Like I do in my Record_from_All.sh script, where I connect the DMICs to Input 1, Headset mic to Input 2, Line In to Input 3 and S/PDIF to Input 4 of AIF1TX{1,2} - the interface to the RPi.

     

    #!/bin/bash
CARD="hw:0"
BEQUIET=" -q "
# Record from onboard DMICs to RPi

# May want to tune the gain here
# Need at least -6dB
amixer ${BEQUIET} -D${CARD} cset name='IN2L Digital Volume' 128
amixer ${BEQUIET} -D${CARD} cset name='IN2R Digital Volume' 128

# DMICs are incorrectly labeled on the board.
# DMICL is actually the right channel and vice versa,
# so we'll swap them here.
# i.e. IN2R --> LHPF1
# IN2L --> LHPF2
# Route DMICs (IN2) to LHPFs.
amixer ${BEQUIET} -D${CARD} cset name='LHPF1 Input 1' IN2R
amixer ${BEQUIET} -D${CARD} cset name='LHPF2 Input 1' IN2L
amixer ${BEQUIET} -D${CARD} cset name='LHPF1 Mode' High-pass
amixer ${BEQUIET} -D${CARD} cset name='LHPF2 Mode' High-pass
amixer ${BEQUIET} -D${CARD} cset name='LHPF1 Coefficients' 240 3
amixer ${BEQUIET} -D${CARD} cset name='LHPF2 Coefficients' 240 3

# Connect outputs of LHPFs to inputs of AIF1 (I2s to RPi)
amixer ${BEQUIET} -D${CARD} cset name='AIF1TX1 Input 1' LHPF1
amixer ${BEQUIET} -D${CARD} cset name='AIF1TX1 Input 1 Volume' 32
amixer ${BEQUIET} -D${CARD} cset name='AIF1TX2 Input 1' LHPF2
amixer ${BEQUIET} -D${CARD} cset name='AIF1TX2 Input 1 Volume' 32

amixer ${BEQUIET} -D${CARD} cset name='DMIC Switch' on

# Record from Headset to RPi
amixer -Dhw:0 cset name='IN1R Volume' 20
amixer -Dhw:0 cset name='IN1 Digital Switch' on

# Route HeadsetMic (IN1) to LHPF.
amixer ${BEQUIET} -D${CARD} cset name='LHPF3 Input 1' IN1R
amixer ${BEQUIET} -D${CARD} cset name='LHPF3 Mode' High-pass
amixer ${BEQUIET} -D${CARD} cset name='LHPF3 Coefficients' 240 3

amixer -Dhw:0 cset name='AIF1TX1 Input 2' LHPF3
amixer -Dhw:0 cset name='AIF1TX1 Input 2 Volume' 32
amixer -Dhw:0 cset name='AIF1TX2 Input 2' LHPF3
amixer -Dhw:0 cset name='AIF1TX2 Input 2 Volume' 32
amixer -Dhw:0 cset name='Headset Mic Switch' on
# This is set up as a dual mono record.

# Record from onboard Line Input to RPi

# +9dB input PGA gain
amixer -Dhw:0 cset name='IN3L Volume' 8
amixer -Dhw:0 cset name='IN3R Volume' 8

# better THD in normal mode vs lower noise floor in high performance
amixer -Dhw:0 cset name='IN3 High Performance Switch' on

amixer -Dhw:0 cset name='IN3L Digital Volume' 128
amixer -Dhw:0 cset name='IN3R Digital Volume' 128

amixer -Dhw:0 cset name='AIF1TX1 Input 3' IN3L
amixer -Dhw:0 cset name='AIF1TX1 Input 3 Volume' 32
amixer -Dhw:0 cset name='AIF1TX2 Input 3' IN3R
amixer -Dhw:0 cset name='AIF1TX2 Input 3 Volume' 32

# Record from SPDIF in

#SPDIF Record:
amixer -Dhw:0 cset name='SPDIF in Switch' on
# switch off SPDIF TX in case already active as
# WM8804 must run at RX rate if enabled

amixer -Dhw:0 cset name='TX Playback Switch' off
amixer -Dhw:0 cset name='RX Playback Switch' on
amixer -Dhw:0 cset name='AIF Playback Switch' on
amixer -Dhw:0 cset name='AIF1TX1 Input 4' AIF2RX1
amixer -Dhw:0 cset name='AIF1TX1 Input 4 Volume' 10
amixer -Dhw:0 cset name='AIF1TX2 Input 4' AIF2RX2
amixer -Dhw:0 cset name='AIF1TX2 Input 4 Volume' 10

    You use the four individual "Volume" controls of the Inputs to set the gain structure - the balance between the four Inputs.

    The "Digital Volume" controls an amplifier that affects all four Inputs in unison, like a kind of Master volume.

     

    And why the value 128 for the "Digital Volume" in all the scripts?

    Looking at the details of a Digital Volume control

    $ amixer ${BEQUIET} -D${CARD} cget name='HPOUT2 Digital Volume'

    numid=156,iface=MIXER,name='HPOUT2 Digital Volume'

      ; type=INTEGER,access=rw---R--,values=2,min=0,max=191,step=0

      : values=128,128

      | dBscale-min=-64.00dB,step=0.50dB,mute=0

    we see that it can be adjusted in 192 steps of 0.5dB each, from -64 to +32.

    -64db + 128 * 0.5dB = 0dB, i.e the value 128 results in unity gain - the signal is neither amplified nor attenuated.

    --

    Ragnar

     

    P.S.

    I have one of these. Note how far the Phones volume control goes image Yup, I'm a geek too...

    image

  • 0 in reply to Former Member

    Thank you very much for the explanation. I have one follow-up question.

     

    I see that the Digital Volume has two values but is set in the examples using only one. That would be natural for balanced channels and is most likely what you would want. But what is the syntax for setting the two values if, for whatever reason, you didn't want them equal?  Would it be as simple as using "120,130" to set th channels differently? And, if that is the case, in what order do they appear?

     

    Bill W

Reply
  • 0 in reply to Former Member

    Thank you very much for the explanation. I have one follow-up question.

     

    I see that the Digital Volume has two values but is set in the examples using only one. That would be natural for balanced channels and is most likely what you would want. But what is the syntax for setting the two values if, for whatever reason, you didn't want them equal?  Would it be as simple as using "120,130" to set th channels differently? And, if that is the case, in what order do they appear?

     

    Bill W

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