## Search found 307 matches

Sat Jun 15, 2019 9:22 am
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 1783

### How DAC works ?

I have some questions about channel 6 DAC mode : 1) do you confirm there's a 9th bit of value at bit 3 of register 2C ? I don't see this register mentioned in most documentations, nor in VGM specs, in particular data blocks are byte based, does it mean that all YM2612 vgm dumps are wrong ? 2) if I w...
Sat Jun 15, 2019 9:14 am
Forum: Sound
Topic: Why change TL before key on ?
Replies: 2
Views: 1070

### Re: Why change TL before key on ?

Thanks, that confirms what I thought!
Sun Jun 09, 2019 7:05 pm
Forum: Sound
Topic: Why change TL before key on ?
Replies: 2
Views: 1070

### Why change TL before key on ?

I'm "disassembling" some VGM from MD games, and notice many weird stuffs. For example, I have something like that : 000000: [channel 1] [operator 3] TL = 16 000000: [channel 1] key off 000000: [channel 1] [operator 3] TL = 8 000000: [channel 1] [operator 3] TL = 29 000000(1FD6): [channel 1] key off ...
Thu May 02, 2019 8:31 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

So, according to this page, it seems that in audio we use the dB for tensions (why ?), which is different (why ?).

So it's indeed 10^(dB/20), which indeed equals roughly 2^(dB/6).

Thanks
Thu May 02, 2019 4:40 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

Your formula is an approximation of mine (with a division by 3 rather than 6, unless I missed something, like efficace value or something like that, which is quite possible).

10^(db/10) = (2^1/log(2))^(db/10) = 2^(db/(10log(2))

and 10log(2) = 3.0103...

Unless the true formula is 10^(db/20) ?
Thu May 02, 2019 4:03 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

Another question : when I translate decibel coordinates to linear ones (whatever they are), I did : attenuation_in_dB = 10*log(I_max/I) where I is my linear amplitude and I_max the maximum amplitude (since I use 16 bits integer, I_max = 32767), which led to : I = I_max*10^(-attenuation_in_dB/10) = I...
Wed May 01, 2019 9:50 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

Stupid me. Of course it makes sense ! Thanks
Wed May 01, 2019 8:35 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

Something I can't find in the above thread (but it may have overlooked it) : In the Envelop Generator, how is the attenuation initialized in the attack phase ? is it 1023 ? if so it means that if TL isn't 0 dB (maximal volume), then operator will remain silent for some time ? or is it initialized at...
Mon Apr 29, 2019 8:53 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

THANK YOU ! I knew this thread, but since it's very technical (and, as I said before, I have absolutely no knowledge in music nor FM synthesis - and generally speaking very few when it comes to hardware), I progressed slowly in reading it and hadn't come to this post. I have to digest all the inform...
Sun Apr 28, 2019 9:37 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

Attack is done with reverse logarithmic slope while other things are done with normal logarithmic slopes. Thanks, it makes perfect sense ! The way envelopes progress is tied to couple LUTs, after every certain amount of samples according to one LUT and ADSR settings, a value from another LUT is add...
Sat Apr 27, 2019 8:32 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

I tried another approach : I created a very simple VGM file, only one note, with variable AR (1 to 8) and TL (0 or 64), played it in various decoders (winamp with vgm reader plugin, Gens) and looked the resulting wav file in Audacity. Some strange things : 1) the results are not exactly the same (ev...
Thu Apr 25, 2019 7:01 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

The limit for AR is 31 tho. It's also instantaneous in that case anyway (since it's the maximum value). This isn't the case that cause me headaches :mrgreen: Also AR/DR/SR/RR all represent slopes (i.e. the angles). Angles, or derivates (i.e. tangent of angles) ? That's more the meaning of "rate" fo...
Thu Apr 25, 2019 6:56 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 5071

### Re: Some beginner questions concerning YM2612

AR is the attack rate, telling you at which speed we raise the Total Level (TL). 63 is a special value so envelop immediately reach the Total Level. The best way to find those information is to analyze sources of YM2612 emulator. I looked into an old (and quite ugly) version of MAME driver (from a ...
Wed Apr 24, 2019 9:49 am
Forum: Exodus
Replies: 6
Views: 1807