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Topic: Mono Playback Volume is very low (about -10dB) (Read 261 times) previous topic - next topic
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Mono Playback Volume is very low (about -10dB)

I have a wav file (16 bit stereo @ 32 kHz rate) from a very old vinyl recording.  As the original record was only mono, I down mixed it to mono, and was surprised that Foobar2000 does not play the file correctly after this change.

I've checked the file in a wav editor and the levels are correct. All other audio applications that I've tested play the mono file at the correct volume. Foobar2000 however plays the mono file at a greatly reduced volume, approx -10dB (or perhaps even less).

There is no replay gain applied to either track (neither original stereo nor down sampled mono), no DSPs are selected, and I've tried all applicable output devices (KS, DS etc) with no change.

Just wondering if this is a known bug?

Foobar version is 1.3.14. BTW

Re: Mono Playback Volume is very low (about -10dB)

Reply #1
foobar2000 plays mono as mono on center channel. You can enable "Convert mono to stereo" DSP to play it on two front speakers instead. On stereo setup there should be no difference in loudness even without using the DSP.

 

Re: Mono Playback Volume is very low (about -10dB)

Reply #2
foobar2000 plays mono as mono on center channel.

Thanks Case :).  I guess that explains it- I don't even have a center speaker connected. I'm just listening with normal headphones btw.

Yeah I had already figured out that using the "mono to stereo" DSP cured the problem, but was unsure why it was necessary. I was trying to figure out why it couldn't just play mono correctly in the first place.

Still wondering if it's wise to assume that someone has a center channel connected, just because they want to play a mono file. I've got a about a million programs on my PC that can play a wav file, and all other 999999 play it without any fuss.

Re: Mono Playback Volume is very low (about -10dB)

Reply #3
Curious about your audio setup. As I mentioned earlier there should be no difference on stereo equipment between real mono and mono mirrored to stereo. Certainly works that way with built-in Windows drivers.

It may be common convention to play mono as stereo but it's not what the source is. Default mode of operation in foobar2000 is to play audio with the exact channel mapping it contains. Nothing is upmixed unless the user asks for it.

Re: Mono Playback Volume is very low (about -10dB)

Reply #4
delete

Re: Mono Playback Volume is very low (about -10dB)

Reply #5
Curious about your audio setup. As I mentioned earlier there should be no difference on stereo equipment between real mono and mono mirrored to stereo. Certainly works that way with built-in Windows drivers.

Ok thanks Case.

- The audio setup is just an onboard "Realtek HD Audio" (ALC888 codec).

- The control panel app is configured for "2 Channel Speakers".

- The Jack is configured for "Headphones Out".

- Also tested with identical results when configured as "Line Out" (with ext headphones amp).

- The Foobar output device is  currently "DS: Primary Sound Driver".

- I have also used "DS: Realtek HD Audio Output" and "KS: Realtek HD Audio Output" and they both work the same as above.

- The estimated volume is about -12 dB for the mono file in each of the above cases.


Re: Mono Playback Volume is very low (about -10dB)

Reply #6
I've just done some more testing and found something interesting. I does appear to be an issue that is specific to the audio hardware. I just plugged in a pair of Logitech USB headphones (and changed the foobar output device to suit) and the volume discrepancy is not apparent on this device.

In another test I used the Realtek control panel app to set the onboard audio to 6 channel and to configure to jack to "Mid/Sub" and sure enough the mono file is played through one channel (the other being the sub). In this configuration there is no audio present (on that center channel) when I play the stereo file. So it does appear to be doing what it's supposed to be doing re the 2 channel versus the 6 channel configuration. Just at reduced volume.

Anyway, using the "Convert mono to stereo" DSP in foobar solves the issue on the Realtek hardware, so I think I'll just leave it at that.

One final question though. Is there any performance penalty for leaving the "mono to stereo" DSP always active in the DSP chain? Will that just be ignored and do nothing when playing content which is already stereo (which is 99.999% of the time).

Thanks. :)

Re: Mono Playback Volume is very low (about -10dB)

Reply #7
It will do nothing unless the audio is mono, in which case it will duplicate it to two channels and call it stereo. This DSP incurs no latency either way, as it requires no extra buffering.

Re: Mono Playback Volume is very low (about -10dB)

Reply #8
Ok thanks Kode54. In that case I'll just leave that DSP active as it solves the issue.

I fear that if I take it out (of the DSP chain) then it's likely to be so long before I even listen to another mono file again that by that time I will have forgotten the solution. ;)

 
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