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Gain and audio distortion in broadcast and recording
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I've got an issue with the gain in general audio settings.
To avoid clipping I decreased the level of my soundcard to -6dB max.
To compensate this and have some extra volume in the broadcasts I increased the gain setting to +9dB in vMix (soundcard level in vMix is 0dB).
But now my broadcasts (FMLE and FFMPEG) have distorted audio when the dB meter in vMix shows 0dB.
(I can not hear any distortion on my headphone on the PC's speaker output)
The soundcards input is not clipping at all.
How is this possible?
I thought that the gain in vMix only compensate for a low source volume and can't increase overall volumes beyond 0db, so why the distortion?
Unfortunately there is only a make up gain so I can't gain first and then use the compressor to limit to -1dB.
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We really need to know the source and a little more detail, but is entirely possible to overdrive audio while registering 0db if the source is overdriven prior to the soundcard.
Can you give us more detail?
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The source is a CD player with a standard line output connected to a Realtek ALC888 onboard soundcard (level 40%).
There is a passive Nano patch volume attenuator (set to 50%) between the two devices.
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I assume mic input?
What does it sound like prior to starting vmix?
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Quote:To avoid clipping I decreased the level of my soundcard to -6dB max.
To compensate this and have some extra volume in the broadcasts I increased the gain setting to +9dB in vMix (soundcard level in vMix is 0dB). How does the audio sound if you do not increase the gain in vMix to +9dB? Have you tried using a USB soundcard/device with a Line Level input? Line level sources going into mic level inputs can cause an impedance mismatch resulting in distorted audio. As kjones9999 mentioned you can have over-driven, distorted audio even while registering 0db or below.
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It is not clear from your description but you may be putting CD output into a mic input. CD output needs to go to a Line input. On most built in Audio Interfaces it is BLUE, Microphone is RED.
Check that out.
Maxi
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wwdv, can you confirm you are running the latest vMix 17 update?
There was a bug a few months back where the gain on recording and streaming ended up being higher than what is heard on the headphones.
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I'm running vMix 17.0.0.105 (Win7 32bit) and using the line input, not the mic input. Without gain the broadcast sounds OK but then the sound level is too low. (because of the low input level to avoid clipping) With maximum gain, the PC's line output (and headphone) sounds still OK, but the broadcast and the recording are distorted. I tried also the Automatic Gain Control and then there is still a little bit distortion. I tested an Audio Genie Pro USB soundcard with the same results. SportsNetUSA.net wrote:Quote:As kjones9999 mentioned you can have over-driven, distorted audio even while registering 0db or below. Can you explain me how this is possible when there is no clipping? And why is the headphone sounding still OK?
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I think I see what might be happening.
Once the audio is received from the audio driver (at whatever format the driver provides) it is immediately
converted to 32bit floating point for all processing in vMix.
With floating point audio you can increase audio above 0dB from within vMix and it won't distort.
But things like streaming require standard 16bit PCM audio, so it is converted back to that format and that is when the distortion might show up.
The sound card may also accept floating point audio which is why it is not distorted there.
To solve this, check the dB level in vMix making sure it doesn't peak above -1dB as a safe level and the distortion should go away.
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OK thanks, that will explain things.
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