* System audio recording have very low amplitude
@ 2020-07-29 9:39 Ariel Elkin
2020-07-29 20:04 ` Jeremy Nicoll - ml sox users
0 siblings, 1 reply; 4+ messages in thread
From: Ariel Elkin @ 2020-07-29 9:39 UTC (permalink / raw)
To: sox-users
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Hello,
I’m using sox to record the audio produced by the system (i.e. from the OS and other running apps), but the recordings sound very quiet.
I first create a virtual input/output device using Blackhole (https://github.com/ExistentialAudio/BlackHole/ <https://github.com/ExistentialAudio/BlackHole/>) or Loopback (https://rogueamoeba.com/loopback/ <https://rogueamoeba.com/loopback/>). I then start playback of a file using iTunes, and start recording thus:
rec --rate 44100 --channels 2 --no dither test-output.aiff
(Note that this spits out the following error messages:
rec WARN formats: can't set sample rate 44100; using 48000
rec WARN formats: can't set 2 channels; using 16
However, test-output.aiff ends up being a stereo file at 44.1 kHz)
test-output.aiff properly records system audio, but the mean amplitude is about half the mean amplitude of the original sounds I played back.
Any thoughts?
Thanks
Ariel
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* Re: System audio recording have very low amplitude
2020-07-29 9:39 System audio recording have very low amplitude Ariel Elkin
@ 2020-07-29 20:04 ` Jeremy Nicoll - ml sox users
0 siblings, 0 replies; 4+ messages in thread
From: Jeremy Nicoll - ml sox users @ 2020-07-29 20:04 UTC (permalink / raw)
To: sox-users
On 2020-07-29 10:39, Ariel Elkin wrote:
> Hello,
>
> I’m using sox to record the audio produced by the system (i.e. from
> the OS and other running apps), but the recordings sound very quiet.
>
> I first create a virtual input/output device using Blackhole
> (https://github.com/ExistentialAudio/BlackHole/
> <https://github.com/ExistentialAudio/BlackHole/>) or Loopback
> (https://rogueamoeba.com/loopback/
> <https://rogueamoeba.com/loopback/>). I then start playback of a file
> using iTunes, and start recording thus:
>
> rec --rate 44100 --channels 2 --no dither test-output.aiff
>
> (Note that this spits out the following error messages:
> rec WARN formats: can't set sample rate 44100; using 48000
> rec WARN formats: can't set 2 channels; using 16
>
> However, test-output.aiff ends up being a stereo file at 44.1 kHz)
>
> test-output.aiff properly records system audio, but the mean amplitude
> is about half the mean amplitude of the original sounds I played back.
What OS are you using? (I see from those links that the apps are MacOS,
which I know nothing about. Someone else might do; also what version?)
Does MacOS have an internal audio mixer that determines the levels of
sound
from various apps and how they go to other devices? There's certainly
one
of those in Windows - so eg if I was going to record audio streamed via
the
BBC's iPlayer and Firefox, I'd start by temporarily turning off the
other
sources of sound that could get in the way (eg the various tones Windows
error-message boxes will play, eg when it insists on telling me that
when
I rename a file it may not work properly in future...). I've found out
that
the hard way, as it's ruined some recordings.
--
Jeremy Nicoll - my opinions are my own
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* Re: System audio recording have very low amplitude
@ 2020-07-30 13:30 Ariel Elkin
2020-07-30 15:01 ` Måns Rullgård
0 siblings, 1 reply; 4+ messages in thread
From: Ariel Elkin @ 2020-07-30 13:30 UTC (permalink / raw)
To: sox-users
> What OS are you using? (I see from those links that the apps are MacOS, which I know nothing about. Someone else might do; also what version?)
I’m using macOS 10.15
> Does MacOS have an internal audio mixer that determines the levels of sound from various apps and how they go to other devices?
No exactly, but there’s an app (Audio MIDI Setup) which will allow you to set the input/output volume and sample rate of your audio hardware. I’ve checked there already and ensured that the input/output volume of Loopback and BlackHole were at 1.
Can someone clarify if this command
rec test-output.aiff
could do any implicit gain attenuation? It’s not clear from the documentation.
Thanks
Ariel
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* Re: System audio recording have very low amplitude
2020-07-30 13:30 Ariel Elkin
@ 2020-07-30 15:01 ` Måns Rullgård
0 siblings, 0 replies; 4+ messages in thread
From: Måns Rullgård @ 2020-07-30 15:01 UTC (permalink / raw)
To: Ariel Elkin; +Cc: sox-users
Ariel Elkin <ariel@arivibes.com> writes:
>> What OS are you using? (I see from those links that the apps are MacOS, which I know nothing about. Someone else might do; also what version?)
>
> I’m using macOS 10.15
>
>> Does MacOS have an internal audio mixer that determines the levels of sound from various apps and how they go to other devices?
> No exactly, but there’s an app (Audio MIDI Setup) which will allow you to set the input/output volume and sample rate of your audio hardware. I’ve checked there already and ensured that the input/output volume of Loopback and BlackHole were at 1.
>
> Can someone clarify if this command
>
> rec test-output.aiff
>
> could do any implicit gain attenuation? It’s not clear from the documentation.
If you add the -V flag, the sox/play/rec commands will list the full
effect chain, including automatically added conversions.
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2020-07-29 9:39 System audio recording have very low amplitude Ariel Elkin
2020-07-29 20:04 ` Jeremy Nicoll - ml sox users
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2020-07-30 13:30 Ariel Elkin
2020-07-30 15:01 ` Måns Rullgård
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