'Twas brillig, and Colin Guthrie at 08/10/10 16:25 did gyre and gimble:
> 'Twas brillig, and Clemens Ladisch at 08/10/10 15:42 did gyre and gimble:
>> Colin Guthrie wrote:
>>> Hmm, just thinking about this (as I don't know the volume control logic
>>> particularly well in PA), the call snd_mixer_selem_set_playback_dB() is
>>> used with a dir argument of +1.
>>>
>>> From what I understand, this would allow me to say "set the volume to
>>> 50dB" and due to the +1 dir, it should select -46.499999 ( because -46.5
>>> mutes it).
>>>
>>> In this case however, the value of -99999.999dB is ultimately selected
>>> (aka 0).
>>>
>>> I'm wondering if the TLV fix actually affects how
>>> snd_mixer_selem_set_playback_dB() call works with the dir argument.
>>
>> Uh, oh. snd_tlv_convert_from_dB() ignores the minimum-is-mute flag.
>
> Ahh good, I analysed that kinda correctly then :D
>
>> Please try this hack:
>>
>> --- alsa-lib/src/control/tlv.c
>> +++ alsa-lib/src/control/tlv.c
>> @@ -335,6 +335,9 @@ int snd_tlv_convert_from_dB(unsigned int *tlv, long rangemin, long rangemax,
>> if (xdir > 0)
>> v += (max - min) - 1;
>> v = v / (max - min) + rangemin;
>> + if (v == rangemin && xdir > 0 && (tlv[3] & 0x10000) &&
>> + db_gain > SND_CTL_TLV_DB_GAIN_MUTE)
>> + v++;
>> *value = v;
>> }
>> return 0;
>
>
> Didn't help sadly, but then looking at the code there it seems a little odd.
>
> Firstly I tried this (extended) patch - I'm not sure it's needed but
> when the first one didn't work I tried to experiment a bit:
>
> --- a/src/control/tlv.c
> +++ b/src/control/tlv.c
> @@ -323,15 +323,20 @@ int snd_tlv_convert_from_dB(unsigned int *tlv,
> long rangemin, long rangemax,
> int min, max;
> min = tlv[2];
> max = tlv[3];
> - if (db_gain <= min)
> + if (db_gain <= min) {
> *value = rangemin;
> - else if (db_gain >= max)
> + if (xdir > 0 && (tlv[3] & 0x10000) && db_gain >
> SND_CTL_TLV_DB_GAIN_MUTE)
> + *value = rangemin + 1;
> + } else if (db_gain >= max)
> *value = rangemax;
> else {
> long v = (db_gain - min) * (rangemax - rangemin);
> if (xdir > 0)
> v += (max - min) - 1;
> v = v / (max - min) + rangemin;
> + if (v == rangemin && xdir > 0 && (tlv[3] &
> 0x10000) &&
> + db_gain > SND_CTL_TLV_DB_GAIN_MUTE)
> + v++;
> *value = v;
> }
> return 0;
>
>
> This also catches the case when I try to set the volume to e.g. -5000
> (-50.00dB) as it is < min (which I presume is still -4650, but actually
> didn't check) then it will be set to rangemin and no further checks are
> done.
>
> What is odd about this tho', is that the flag for min is mute (0x10000)
> is checked on tlv[3] which is also used here for the "max" value.
>
> Is the use of position 3 correct (both here and on the kernel side) or
> perhaps the max line needs to be:
>
> max = (tlv[3] & 0xffff);
>
> instead? Either way it didn't help, but I thought the strangeness with
> the tlv[3] value was worth pointing out.
>
> Many thanks for debugging this with me :)
>
> Col
>
> PS, happy to chat on IRC if you prefer - coling
Ignore this mail... I applied the patch to the wrong tree and it put the
hunks in a different place as the context was a 100% match...
I'll retest with this applied correctly! Sorry :D
Col
--
Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/
Day Job:
Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
Mageia Contributor [http://www.mageia.org/]
PulseAudio Hacker [http://www.pulseaudio.org/]
Trac Hacker [http://trac.edgewall.org/]
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