[alsa-devel] [BUG] Bad decibel data on C-Media USB sound card
Raymond Yau wrote:
Does this number of steps remain the same when your starting volume are
not at 151?
Your value 77 seem quite different from alsamixertest
recording a sine wave with an amplitude of 1 in Audacity at step 151 shows that the recorded value is amplitude 0.885. Does this indicates some loss? The loopback cable I am using is 2 meters in length, is the resistance of the cable is too high?
Does this number of steps remain the same when your starting volume are
not at 151?
Your value 77 seem quite different from alsamixertest
recording a sine wave with an amplitude of 1 in Audacity at step 151
shows that the recorded
value is amplitude 0.885. Does this indicates some loss? The loopback
cable I am using
is 2 meters in length, is the resistance of the cable is too high?
Did you use mono or stereo in playback and capture?
Did your capture volume /boost set to 0dB?
Do your sound card support the sampling rate ?
It depends on frequency of sine wave, sampling rate, playback gain/atten capture gain/atten
http://wiki.linuxaudio.org/apps/all/jaaa
Do the frequency response of your card look like a straight line at 0dB similar to those cards loopback test ?
http://audio.rightmark.org/test_results.shtml
Refer to the datasheet and your alsamixertest result , the card seem not has fixed gain for each step
You many need to change the name of the volume control to headphone playback volume in alsamixertest Done. alsamixertest output:http://ix.io/ezd
Are you using version 48.11?
Seem alsamixertest is not suitable for testing volume control with less than 1dB per step or variable dB per step
participants (2)
-
Allen M. -
Raymond Yau