[alsa-devel] [BUG] Bad decibel data on C-Media USB sound card
Raymond Yau wrote:
Do the automatic gain has any side effect when it normalise the volume?
I am unsure of how to go about testing that, 'alsamixer' does not appear to allow me to modify automatic gain.
Do you mean the sound card does not has 7248 steps?
I am not familiar with how to properly check, however dbverify indicates 'Element volume range is 0..151 (-28.37..-0.06 dB).'
Instructions for dbmeasure on the wiki indicates the need for a Line In, the sound card only provides Line Out and Mic In. Will it automatically make use of 'Mic In' if 'Line In' is absent? Or do I even need to use it?
You need to find out the value of c->res As you complain dB range -28.37 to -0.06 are not correct
Quick testing done with dbverify: http://ix.io/eyi
You need to calibrate the dB range
Volume Steps <=3 are mute while volume step 4 is audible, based on dbverify testing. This 'seems' to indicate that the minimum volume is somewhere between -27.81 dB to -27.63 dB?
Additional info logs: Output of 'amixer -c2 contents': http://ix.io/eyq Alsa info script output: http://ix.io/eyn
Do the automatic gain has any side effect when it normalise the volume?
I am unsure of how to go about testing that, 'alsamixer' does not appear to allow me to modify automatic gain.
You have to specify card number
It affect your measurent if you are using the mic on your usb audio if the automatic gain control is switch on
Do you mean the sound card does not has 7248 steps?
I am not familiar with how to properly check, however dbverify indicates 'Element volume range is 0..151 (-28.37..-0.06 dB).'
Instructions for dbmeasure on the wiki indicates the need for a Line In, the sound card only provides Line Out and Mic In. Will it automatically make use of 'Mic In' if 'Line In' is absent? Or do I even need to use it?
Background noise affect the result if you are not using line in and line out with a loopback cable , this mean you have to minimize the background noise
You need to find out the value of c->res As you complain dB range -28.37 to -0.06 are not correct
Quick testing done with dbverify:http://ix.io/eyi
You need to calibrate the dB range
Volume Steps <=3 are mute while volume step 4 is audible, based on dbverify testing. This 'seems' to indicate that the minimum volume is somewhere between -27.81 dB to -27.63 dB?
How many steps need to reduce amplitude of the recorded sine wave by half when you play a sine wav through your usb audio and record it back using audacity?
http://mailman.alsa-project.org/pipermail/alsa-devel/2010-September/032016.h...
You many need to change the name of the volume control to headphone playback volume in alsamixertest
Additional info logs: Output of 'amixer -c2 contents':http://ix.io/eyq Alsa info script output:http://ix.io/eyn
participants (2)
-
Allen M. -
Raymond Yau