Recent Posts

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21
Development Corner / Re: Mixing channels
« Last post by bass on May 28, 2017, 20:52:34 »
Thanks for the competent answers!
Last question: How is this solved in OpenMPT? Just manual setting?
22
Development Corner / Re: Mixing channels
« Last post by Saga Musix on May 28, 2017, 18:53:16 »
To give some ideas:
What e.g. XMPlay/BASS.DLL does is rendering a very low-quality version of the module while it's loading which gives a pretty good estimation of how loud the module will be in total. This is then used as an amplification factor.
However, apart from simple normalization, a module player really should not modify the dynamic range of modules. The dynamic range should be under full control of the artist.
23
Help and Questions / Re: MIDI Library Instruments; why can't I use them?
« Last post by Saga Musix on May 28, 2017, 18:48:02 »
Be sure that you are dragging them into the black area in the sample or instrument editor. If that doesn't work, verify that there is actually an instrument filename (typically GM.DLS) next to the instrument name in the MIDI library. When installing e.g. on Linux via Wine, the default soundfont GM.DLS is not available. These samples are not a part of OpenMPT itself but rather the system.
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Help and Questions / Re: MIDI Library Instruments; why can't I use them?
« Last post by Andarus443 on May 28, 2017, 18:39:56 »
Alright, so why can't I drag and drop instruments?
25
Development Corner / Re: Mixing channels
« Last post by manx on May 28, 2017, 18:22:09 »
mixing channels in theory is just adding the samples and dividing by channelcount. There is enough headroom to avoid clipping. But if we have 32 channels, the output signal is very quiet and we have too much headroom in this case. So, which formula or method is useful in these cases? Hard limiting? Compression? Is there an easy and good sounding way?

For file formats or situations that specify an actual global volume or amplification factor, the problem of reaching the desired target volume is basically transferred to the user.

In all other cases any player generally resorts to some sort of heuristic of which the "divide by channelcount" is one possible heuristic but not a very good one. The mixed signal (as a rule of thumb) increases by roughly 3dB instead of 6dB on average.

Dynamic range compression or hard limiting is a separate concern that can be applied after mixing anyway in order to mitigate clipping/distortion caused by going over 0dBFs.

Also, if the number of mixed channels varies over time (like for example in the situation of the Windows system audio mixer), you cannot even apply any heuristic based on channel count. Thus, no channel gets attenuated at all and the result is just a plain addition of the source signals. Windows applies a hard limiter to the result in order to avoid clipping.

And why do many players use floating sample data (-1..0..1) and not i.e. 32 bit integer data for calculations? Is there a big difference in sound quality or is it just simpler to convert the floating data to real output format?

Floating point data is generally easier to work with because you can basically ignore any data type overflow issues if the signal is too loud or quantization distortion if the signal is too quiet.

Sound quality wise, 32bit float vs. 32bit integer does not make any practical difference. Both provide more dynamic range than the human ear can resolve.
26
Development Corner / Mixing channels
« Last post by bass on May 28, 2017, 18:06:04 »
Hi,

mixing channels in theory is just adding the samples and dividing by channelcount. There is enough headroom to avoid clipping. But if we have 32 channels, the output signal is very quiet and we have too much headroom in this case. So, which formula or method is useful in these cases? Hard limiting? Compression? Is there an easy and good sounding way?

And why do many players use floating sample data (-1..0..1) and not i.e. 32 bit integer data for calculations? Is there a big difference in sound quality or is it just simpler to convert the floating data to real output format?

Thanks!
27
Help and Questions / Re: MIDI Library Instruments; why can't I use them?
« Last post by Saga Musix on May 28, 2017, 16:35:13 »
The MIDI library's purpose is to provide a default instrument set for MIDI import. If you double-click one of its entries, you can replace these instruments so that MIDI import uses different ones. You can drag&drop any items from the MIDI library into the sample or instrumen editor to use them in other cases, though.
Note that by default, the MIDI library uses the GM.DLS sound library that is shipped with Windows, so its content is not any different from the GM.DLS folder right below it (which you can indeed double-click to preview sounds).
28
General Chatter / Re: Please recommend me a sample pack
« Last post by Saga Musix on May 28, 2017, 16:24:46 »
They are all either 8SVX samples (which OpenMPT can read natively) or raw PCM data. In the latter case, you choose 8-bit, signed, mono in the import dialog.
29
General Chatter / Re: Please recommend me a sample pack
« Last post by darkhog on May 28, 2017, 16:16:13 »
How do I import them to OpenMPT? They're in an unknown format.
30
Help and Questions / MIDI Library Instruments; why can't I use them?
« Last post by Andarus443 on May 28, 2017, 16:10:46 »
So I'm brand new to the software and completely lost. There's the file folder labeled MIDI Library and it lists all of these seemingly great instruments to use... that don't exist if you double click on them. If I double click it opens up a selection window that lists all of these weird samples that have nothing to do with the instruments listed in MIDI Library. What is this, how do I use MIDI Library if it's something other than a cruel taunt, what am I even looking at?!
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