[alsa-devel] 2 speakers are assigned to the same DAC, this can't support 4.0/2.1 channles

[Raymond Yau]

>>>>>>>
>>>>>>> I am trying to enable the subwoofer speaker on a HP laptop, on this
>>>>>>> machine, there are two speakers and one headphone, but the BIOS verb
>>>>>>> only enabled one speaker(nid 0xd) and one headphone(nid 0xb), I need
>>>>>>> to use quirk in the kernel driver to configure the second speaker
>>>>>>> (subwoofer speaker, nid 0x10). Under current alsa driver, the
>>>>>>> headphone will be assigned a dac (nid 0x13) and the 2 speakers will
>>>>>>> be assigned a dac (nid 0x14), this assignment is not good since 2
>>>>>>> speakers share the same dac, this means 2 speakers can't work
>>>>>>> at the same time to support 4.0/2.1 channels.
>>>>>>>
>>>>>>> On another Dell machine with realtek codec, there are also 2
speakers,
>>>>>>> 1 headphone and 2 dacs, on this machine, 1 speaker and 1 headphone
are
>>>>>>
>>>>>> assigned
>>>>>>>
>>>>>>> 1 dac, and the other speaker is assigned another dac, so there is no
>>>>>>> problem for this machine to support 4.0/2.1 channels.
>>>>>>>
>>>>>>> Through debugging, I found on Dell machine, the speaker nid only has
>>>>>>> one connection to dac (hardwired), so when driver assign dac to it,
>>
>> the
>>>>>>>
>>>>>>> map_single() can successfully assign the each dac to the 2 speakers
>>>>>>
>>>>>> respectively.
>>>>>>>
>>>>>>> But on that HP machine, the speaker has multiple connections for
dac,
>>>>
>>>> the
>>>>>>>
>>>>>>> map_single() can't work for this machine.
>>>>>>>
>>>>>>>
>>>>>>> The alsa-info.txt for that HP machine is at
>>>>>>
>>>>>> http://pastebin.ubuntu.com/11667947/
>>>>>>
>>>>>> Refer to 92HD91, you don't need 4 channel when there is band pass
>>
>> filter
>>>>>>
>>>>>> for the subwoofer at the mono pin
>>>>>
>>>>> Yes, you are right.
>>>>>
>>>>>> 2.2. Mono Output
>>>>>> The Mono Out port source selection, power state, and mute
>>
>> characteristics
>>>>>>
>>>>>> are all independently
>>>>>> controlled by the mono output port controls. EQ does not apply to
this
>>>>>> path. An internal 2nd order band-pass filter is provided to restrict
>>
>> the
>>>>>>
>>>>>> output frequencies when using mono out to drive an exter-
>>>>>> nal amplified sub-woofer
>>>>>
>>>>> Where did you find this text? Does it mean there is a hardware low
>>>>
>>>> frequency pass filter inside the codec?
>>>>
>>>> http://www.temposemi.com/products/pclaptop-hd/92hd91/
>>>>
>>>> 2.3. Mono output Band-Pass Filter
>>>> For many applications, the primary speakers are incapable of
reproducing
>>>> low frequency audio. Therefore it is desirable to implement a woofer or
>>>> sub-woofer speaker. The mono output is ideal for this task. However,
the
>>>> frequency response should be restricted to prevent interference with
the
>>>> primary speakers. Typically an external filter, known as a cross-over
>>>> filter, is used. The mono processing path includes a band-pass filter
>>
>> with
>>>>
>>>> programmable high and low cut-off frequencies to eliminate the need for
>>
>> an
>>>>
>>>> external filter.
>>>>
>>>> 2.3.1. Mixer Filter Description The band-pass filter is derived from
the
>>>> common biquadratic filter and provides a 12dB/octave roll-off. The
filter
>>>> may be programmed for a -3dB lower band edge of: 63Hz, 80Hz, 100Hz,
>>
>> 120Hz,
>>>>
>>>> 150Hz, 200Hz, 315Hz, or 400Hz.
>>>>
>>>> The filter may be programmed for a -3dB upper band edge of: 150Hz,
200Hz,
>>>> 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, or 800Hz.
>>>>
>>>> The band-pass filter is enabled by default with a cut-off frequencies
at
>>>> 120Hz and 250Hz. The filter may be bypassed using the associated verb
>>>> (processing state verb
>>>
>>> Thanks very much, very useful information.
>>>
>>>
>> Do your codec revision support this mono out volume ?
>>
>> 7.4.31.AFG (NID = 01h): DAC3OutAmp (Mono Out Volume)
>
> I looks like the current driver does not use this to control the volume.
>
>>
>> How do you assign the two volume control to headphone, speaker and
>> subwoofet ?
>
> speaker and headphone are assigned to DAC0 (nid: 0x13), they use the DAC
amplifier to control the volume.
>
> subwoofer speaker is assigned to DAC1 (nid: 0x14), it use the DAC
amplifier to contorl the volume.
>

Do pulseaudio like this config since there is no mute switch at pin complex
of idt codecs and no headphone playback volume/switch?

After applied your patch

Front playback volume/switch are shared by headphone and speaker
Base speaker playback volume/switch

But the other 4 channels  hda codecs vt1802 have speaker playback switch
and subwoofer playback switch

http://git.kernel.org/cgit/linux/kernel/git/tiwai/hda-emu.git/tree/codecs/vt1802-asus-g75