3 Dec
2003
3 Dec
'03
1:25 p.m.
DC offset is when there is a Direct Current running over the same lines that audio runs
through. Since sound signals are a type of Alternating Current, the addition of the DC
tends to shift, or offset, the audio signal.
regards
-Reuben
-----Original Message-----
From: Eric Dantan Rzewnicki [mailto:rzewnickie@rfa.org]
Sent: Wednesday, December 03, 2003 11:10 AM
To: A list for linux audio users
Subject: [linux-audio-user] what is DC? [was Re: Analyzing ogg files]
What is DC offset in this context? I've seen this term on this list
before, but don't really understand what it means.
Is this the same thing refered to by the ecasound options -ezf and -ezx?
-ezf
Finds the optimal value for DC-adjusting. You can use the result as
a parameter to -ezx effect.
-ezx:channel-count,delta-ch1,...,delta-chN
Adjusts the signal DC by 'delta-chX', where X is the channel number.
Use -ezf to find the optimal delta values.
or is that a different DC?
-Eric Rz.
On Tue, Dec 02, 2003 at 07:38:54PM -0800, Mark Knecht wrote:
On Tue, 2003-12-02 at 13:06, Andrew Burgess wrote:
More data, but I'm not sure there's an answer there yet. The first file
creates a very loud glitch sound, which the second one doesn't. The
midline value seems better on the first, assuming this represents DC
offset.
bash-2.05b$ sox gmc2.ogg -e stat
Samples read: 26972160
Length (seconds): 305.806803
Scaled by: 2147483647.0
Maximum amplitude: 0.999969
Minimum amplitude: -1.000000
Midline amplitude: -0.000015
Mean norm: 0.138033
Mean amplitude: 0.000003
RMS amplitude: 0.189967
Maximum delta: 0.959961
Minimum delta: 0.000000
Mean delta: 0.093997
RMS delta: 0.128996
Rough frequency: 4766
Volume adjustment: 1.000
bash-2.05b$ sox examplesustain.ogg -e stat
Samples read: 11361130
Length (seconds): 128.810998
Scaled by: 2147483647.0
Maximum amplitude: 0.649841
Minimum amplitude: -0.661896
Midline amplitude: -0.006027
Mean norm: 0.069344
Mean amplitude: 0.002177
RMS amplitude: 0.092420
Maximum delta: 0.784546
Minimum delta: 0.000000
Mean delta: 0.072115
RMS delta: 0.095279
Rough frequency: 7235
Volume adjustment: 1.511
bash-2.05b$
> Is
there a DC offset which the cheap card is eating?
A DC offset is an interesting idea. How would I
test for that?
sox <file> -e stat
displays midline amplitude.
Or try a highpass filter, just as a test.