Rybags Posted July 31, 2009 Share Posted July 31, 2009 (edited) Continuing on from this old thread http://www.atariage.com/forums/index.php?showtopic=116835 I don't know if it's common knowledge, but this is how the Triangle waveform works on Atari... We set voices 1 and 3 to 1.79 MHz mode, then put 2 similar values into AUDF1 and AUDF3. The actual triangle wave is produced thanks to the phasing effect/interaction between the two high frequencies playing on the two voices. Since the speaker has no chance of playing back two extremely high notes, instead we get a kind of "averaging" similar to the way PWM works. Now... deducing what frequency is playing? Easy. With phasing, the frequency of the effect is deduced by ABS(Freq1 - Freq2) or, in the case of our Triangle Wave, ABS(AUDF1-AUDF3) The range of values we can use for our AUDF1/3 is kinda limited. Once we get around the mid 70s or so, the original high pitch of that sound becomes audible. Values below 20, well high-pitched triangle waves tend to sound almost identical to square waves of the same frequency, so why bother using 2 voices to produce what we can with one? Also, this formula and table should work fine with the sawtooth waveform. Anyhow, with a quick BASIC program, we can produce some data which I've imported into Excel and sorted by Frequency. [b] Audf1 Audf3 Freq Audf equivalent in 8-bit 64 KHz mode[/b] 75 76 140.3 224.714207 74 75 143.9 219.071426 73 74 147.64 213.500014 72 73 151.52 208.000087 71 72 155.57 202.571331 70 71 159.77 197.214285 69 70 164.15 191.928642 68 69 168.71 186.714292 67 68 173.46 181.571442 66 67 178.42 176.499991 65 66 183.59 171.499949 64 65 188.99 166.571475 63 64 194.63 161.71423 62 63 200.53 156.928603 61 62 206.7 152.214251 60 61 213.15 147.571489 59 60 219.92 143.000001 58 59 227.02 138.499966 57 58 234.46 134.071419 56 57 242.27 129.714274 55 56 250.49 125.428603 54 55 259.12 121.214258 53 54 268.22 117.071439 75 77 277.14 113.267856 52 53 277.8 112.999992 74 76 284.21 110.428551 51 52 287.9 109.000015 73 75 291.54 107.625003 50 51 298.56 105.071428 72 74 299.16 104.857168 71 73 307.09 102.124996 49 50 309.83 101.214292 70 72 315.34 99.428547 48 49 321.74 97.4285482 69 71 323.92 96.7678752 68 70 332.85 94.1428761 47 48 334.36 93.7143122 67 69 342.17 91.5535767 46 47 347.73 90.0714038 66 68 351.87 89.0000011 45 46 361.93 86.5000142 65 67 362 86.4821275 64 66 372.57 83.9999997 44 45 377.01 82.9999978 63 65 383.61 81.5535685 43 44 393.05 79.5714278 62 64 395.15 79.1428519 61 63 407.22 76.7678562 42 43 410.14 76.2142817 75 78 410.65 76.1190441 60 62 419.85 74.4285789 74 77 421.05 74.2142849 41 42 428.37 72.9285783 73 76 431.85 72.3333265 59 61 433.08 72.1250152 72 75 443.07 70.476202 58 60 446.94 69.8571345 40 41 447.84 69.7142779 71 74 454.73 68.642857 57 59 461.47 67.6249894 70 73 466.86 66.8333317 39 40 468.67 66.5714322 56 58 476.73 65.4285664 69 72 479.48 65.0476171 38 39 490.99 63.5000053 68 71 492.62 63.2857229 55 57 492.76 63.2678629 67 70 506.31 61.5476289 54 56 509.61 61.1428579 37 38 514.94 60.4999943 66 69 520.58 59.8333345 53 55 527.34 59.0535676 65 68 535.46 58.1428516 36 37 540.69 57.5714242 75 79 540.93 57.5446361 52 54 546.01 57.0000007 64 67 550.99 56.4761894 74 78 554.55 56.1071407 51 53 565.69 54.982145 63 66 567.2 54.8333266 35 36 568.41 54.7142856 73 77 568.69 54.6875006 72 76 583.37 53.2857164 62 65 584.14 53.2142882 50 52 586.46 53.0000037 34 35 598.33 51.9285755 71 75 598.63 51.9017855 61 64 601.85 51.6190414 49 51 608.39 51.0535731 70 74 614.5 50.5357142 60 63 620.38 50.0476258 33 34 630.67 49.2142818 69 73 631.01 49.1875039 48 50 631.57 49.1428526 59 62 639.77 48.5000034 68 72 648.19 47.8571422 47 49 656.1 47.2678584 58 61 660.09 46.976193 32 33 665.71 46.5714309 67 71 666.08 46.5446485 75 80 668.12 46.399997 57 60 681.4 45.4761858 46 48 682.1 45.4285713 66 70 684.73 45.2500047 74 79 684.83 45.2428528 73 78 702.19 44.0999993 31 32 703.75 44.0000005 56 59 703.75 43.9999941 65 69 704.17 43.9732115 45 47 709.66 43.6249977 72 77 720.21 42.9714328 64 68 724.45 42.7142859 55 58 727.22 42.5476207 44 46 738.94 41.8571457 71 76 738.94 41.8571399 30 31 745.15 41.4999998 63 67 745.62 41.4732099 54 57 751.89 41.1190468 70 75 758.4 40.7571427 62 66 767.73 40.2499985 43 45 770.06 40.1249993 53 56 777.83 39.7142873 69 74 778.65 39.6714316 29 30 790.31 39.071431 61 65 790.83 39.0446419 75 81 792.31 38.9702342 68 73 799.71 38.6000027 42 44 803.19 38.4285702 52 55 805.14 38.3333308 74 80 812.02 37.9999979 60 64 815 37.8571436 67 72 821.65 37.5428574 73 79 832.47 37.0416642 51 54 833.91 36.9761926 41 43 838.51 36.767858 28 29 839.7 36.7142849 59 63 840.3 36.6875038 66 71 844.5 36.5000031 72 78 853.71 36.0952404 50 53 864.25 35.6428581 58 62 866.79 35.5357138 65 70 868.32 35.4714292 71 77 875.78 35.1607141 40 42 876.21 35.1428567 64 69 893.15 34.4571432 27 28 893.87 34.4285712 57 61 894.55 34.4017864 49 52 896.28 34.3333357 70 76 898.71 34.2380932 39 41 916.51 33.5535705 63 68 919.08 33.4571404 69 75 922.55 33.3273831 56 60 923.67 33.285711 48 51 930.13 33.047617 62 67 946.14 32.4714273 68 74 947.35 32.4285737 26 27 953.47 32.2142832 55 59 954.24 32.187499 38 40 959.66 32.0000022 47 50 965.93 31.7857155 67 73 973.17 31.5416689 61 66 974.42 31.4999975 54 58 986.34 31.1071418 66 72 1000.06 30.6666665 46 49 1003.84 30.5476166 60 65 1003.99 30.5428593 37 39 1005.93 30.4821426 25 26 1019.22 30.0714289 53 57 1020.1 30.0446431 65 71 1028.09 29.8035719 59 64 1034.92 29.6000005 45 48 1044.02 29.333335 36 38 1055.62 28.9999975 52 56 1055.62 29.0000003 64 70 1057.3 28.9523829 58 63 1067.31 28.6714294 44 47 1086.67 28.1428559 63 69 1087.78 28.1130937 24 25 1092.02 28.0000003 51 55 1093.03 27.9732139 57 62 1101.25 27.7571421 35 37 1109.1 27.5535703 62 68 1119.6 27.2857137 43 46 1131.99 26.9761916 50 54 1132.47 26.9642868 56 61 1136.83 26.8571428 61 67 1152.84 26.4702361 34 36 1166.74 26.1428582 23 24 1172.91 25.9999995 49 53 1174.08 25.9732152 55 60 1174.16 25.971428 42 45 1180.2 25.8333325 60 66 1187.58 25.666667 54 59 1213.36 25.0999981 48 52 1218.03 24.9999996 59 65 1223.91 24.8750015 33 35 1229 24.7678571 41 44 1231.56 24.714286 53 58 1254.56 24.242857 58 64 1261.94 24.0952373 22 23 1263.14 24.0714283 47 51 1264.49 24.0446436 40 43 1286.35 23.619047 32 34 1296.38 23.4285711 52 57 1297.9 23.3999998 57 63 1301.77 23.3273812 46 50 1313.66 23.1071418 51 56 1343.52 22.5714295 56 62 1343.52 22.5714277 39 42 1344.88 22.5476193 21 22 1364.19 22.2142856 45 49 1365.77 22.1874997 31 33 1369.46 22.1250007 55 61 1387.31 21.8273819 50 55 1391.59 21.7571426 38 41 1407.5 21.5000002 44 48 1421.03 21.285715 54 60 1433.28 21.0952368 49 54 1442.3 20.9571438 30 32 1448.89 20.8571429 37 40 1474.6 20.4761907 20 21 1477.87 20.4285714 43 47 1479.72 20.401785 53 59 1481.58 20.3749991 48 53 1495.82 20.1714281 52 58 1532.36 19.6666663 29 31 1535.45 19.6250006 42 46 1542.13 19.5357146 36 39 1546.61 19.4761898 47 52 1552.39 19.400001 51 57 1585.79 18.9702385 41 45 1608.57 18.6875 46 51 1612.22 18.6428564 35 38 1624.04 18.4999989 28 30 1630.01 18.4285718 50 56 1642.08 18.2857149 45 50 1675.59 17.9 40 44 1679.4 17.8571424 49 55 1701.42 17.6130953 34 37 1707.43 17.5476191 27 29 1733.57 17.2678569 44 49 1742.77 17.1714282 39 43 1755.02 17.0446428 48 54 1764.04 16.9523808 33 36 1797.41 16.6190476 43 48 1814.08 16.4571432 47 53 1830.18 16.303572 38 42 1835.87 16.2500005 26 28 1847.34 16.1428564 42 47 1889.86 15.7571422 32 35 1894.71 15.7142859 46 52 1900.12 15.6666665 37 41 1922.44 15.473214 41 46 1970.5 15.0714291 25 27 1972.69 15.0535709 45 51 1974.15 15.0416666 31 34 2000.13 14.8333332 36 40 2015.28 14.7142855 44 50 2052.6 14.4285713 40 45 2056.41 14.3999996 24 26 2111.25 14.0000001 30 33 2114.6 13.9761907 35 39 2115.02 13.9732139 43 49 2135.83 13.8273807 39 44 2148.07 13.742857 34 38 2222.36 13.2499997 42 48 2224.22 13.2380953 29 32 2239.2 13.1428574 38 43 2246.01 13.1000002 23 25 2264.94 12.9821428 41 47 2318.23 12.6607141 33 37 2338.1 12.5446426 37 42 2350.8 12.4714286 28 31 2375.15 12.3333335 40 46 2418.34 12.0952381 22 24 2436.05 11.9999998 32 36 2463.12 11.857143 36 41 2463.12 11.8571424 27 30 2523.88 11.5476191 39 45 2525.08 11.5416665 35 40 2583.69 11.2571427 31 35 2598.46 11.1875001 21 23 2627.33 11.0535713 38 44 2639.06 11.0000001 26 29 2687.04 10.7857138 34 39 2713.35 10.6714285 30 34 2745.27 10.5357142 37 43 2760.95 10.470238 20 22 2842.06 10.1428571 33 38 2853.04 10.0999996 25 28 2866.56 10.0476188 36 42 2891.49 9.95238084 29 33 2904.91 9.90178604 32 37 3003.81 9.54285711 35 41 3031.53 9.44642833 24 27 3064.71 9.33333318 28 32 3078.9 9.28571441 31 36 3166.87 9.00000012 34 40 3182.02 8.95238103 27 31 3269.03 8.68750007 23 26 3284.16 8.64285716 30 35 3343.6 8.47142867 33 39 3344.02 8.47023796 26 30 3477.35 8.10714274 32 38 3518.74 7.99999985 22 25 3528.08 7.97619043 29 34 3535.58 7.95714295 25 29 3706.26 7.54464267 31 37 3707.55 7.54166666 28 33 3744.61 7.45714301 21 24 3800.24 7.33333326 30 36 3912.02 7.09523817 24 28 3958.59 6.99999989 27 32 3972.78 6.97142863 20 23 4105.2 6.71428568 29 35 4133.91 6.66071444 26 31 4222.49 6.49999991 23 27 4237.63 6.47321417 28 34 4375.28 6.23809527 25 30 4496.57 6.04285709 22 26 4547.3 5.9642857 27 33 4638.48 5.82738105 24 29 4798.29 5.5999999 21 25 4892.27 5.47321426 26 32 4926.24 5.42857137 23 28 5131.5 5.17142848 25 31 5241.72 5.04166662 20 24 5278.12 4.99999996 22 27 5500.77 4.75714277 24 30 5588.59 4.66666664 21 26 5911.49 4.35714285 23 29 5971.2 4.30357135 20 25 6370.14 3.97142855 22 28 6394.64 3.95238088 21 27 6864.96 3.61309518 20 26 7389.36 3.28571428 I've generated values for differences in AUDF1/3 up to 6 - all that's needed really. By incorporating the values into table, we could have a nice sliding frequency scale, or by using selected values equivalent to musical notes, we can use triangle waves for music. Proof of the formula? Pretty easy actually. The last column of values contains the AUDF value you need to approximate the same frequency if you're in normal 64 KHz mode. By playing our triangle and a quiet normal pure tone on another voice, we can get a phasing effect which proves that the frequencies are close in value. e.g. try this stuff in BASIC (real machine needed here). You can't use Sound commands because they always clear AUDCTL, and we don't want that: POKE 53768,96:POKE 53775,3 POKE 53761,175:POKE 53765,175 POKE 53760,54:POKE53764,55 POKE 53766,121:POKE 53767,162 Try other values from rows in the table. The values to POKE are as follows: AUDF1 into 53760 AUDF3 into 53764 Put the "Audf equivalent values" into 53766. For the sawooth instead of triangle wave, POKE 53768,100 The program I used to generate the table is pretty short and simple. I directed the output to "P:" then imported into Excel and sorted by Frequency. 10 BASE=14187576/8 20 FOR DIFF=1 TO 6 30 FOR AUDF1=20 TO 75 40 AUDF3=AUDF1+DIFF 50 FR1=BASE/((AUDF1+4)*2):FR3=BASE/((AUDF3+4)*2) 70 FREQ=ABS(FR1-FR3) 80 F=INT(FREQ*100+0.5)/100 90 F64=BASE/56/FREQ-1 180 ? AUDF1;",";AUDF3;",";F;",";F64 190 NEXT AUDF1 290 NEXT DIFF What next? Well, it'd be nice to work out what's going on in two-tone mode. Maybe we could get some formulas and tables for doing variable pulsewidth square waves. Edited July 31, 2009 by Rybags 1 Quote Link to comment Share on other sites More sharing options...
Bryan Posted July 31, 2009 Share Posted July 31, 2009 What next? Well, it'd be nice to work out what's going on in two-tone mode. Maybe we could get some formulas and tables for doing variable pulsewidth square waves. I've been meaning to dig out my old 2-tone notes. Basically you can pick any freq. for a square wave, and then vary the duty-cycle from 50 to 75% in small increments. This allows you to slide from a "fat" to "thin" sounding tone and back again. I also had done some work on getting the best performance from the triangle mode, but lost it all in a hard drive crash. There are two issues I was working on. The first one was getting the most output possible, and the second one was eliminating the 'pop' (DC offset) that tended to happen at the start of triangle notes. I would very much like to go back and revisit these topics when I have the time. Quote Link to comment Share on other sites More sharing options...
emkay Posted July 31, 2009 Share Posted July 31, 2009 All calculations with sawtooth, triangles... whatever, are only useful, if we can grant the same pase shifting everytime when a note gets played. POKEY starts at least the generators at the same time, when filter is used. So it is simply necessary in RMT to play both voices 2 times on the envelop at the highest pitch, to have them always in the same phase and same shift. In 16 bit, we don't have the chance to do the same in RMT. Possibly, if doing something like using all 16 bit annd filters on and repeat the "initial" several times, until all fits together... but in practice this wouldn't be much useful. btw: High pitched squarewaves. They clearly sound less "yelling" and with a different pitch of the filtervoice, you can get frequency steps between (higher than) the 8 bit resolution. Lower pitched triangles and waves, you simply can create them by using a programmed phase offset in 15 and 64khz mode.... as I had shown in another thread: http://www.atariage.com/forums/index.php?s...=complex+sounds Quote Link to comment Share on other sites More sharing options...
thorfdbg Posted July 31, 2009 Share Posted July 31, 2009 Continuing on from this old thread http://www.atariage.com/forums/index.php?showtopic=116835 I don't know if it's common knowledge, but this is how the Triangle waveform works on Atari... We set voices 1 and 3 to 1.79 MHz mode, then put 2 similar values into AUDF1 and AUDF3. The actual triangle wave is produced thanks to the phasing effect/interaction between the two high frequencies playing on the two voices. Since the speaker has no chance of playing back two extremely high notes, instead we get a kind of "averaging" similar to the way PWM works. Not quite. If "averaging" would work as you call it, you wouldn't hear anything. Averaging is linear superposition, and a linear superposition of two high frequency waves is just that - two high frequency waves. The reason why you do hear something is that there is a nonlinearity in the path between the pokey output and the speaker, and it's not the speaker. (-; High frequencies are cut-off before they even reach it. It is a nonlinearity in Pokey's analog parts that creates this effect - it's a rather low-cost silicon device that wasn't designed for high-fidelity audio. If you pick this sound up with a scope, I bet you would also see something considerably different from triangle - but at least a symmetric shape - meaning only "odd harmonics" are present giving it a sound that is close to a triangle. The volume is much lower because the amplitude of the mixing depends on the degree of nonlinearity - and Pokey is only a bit, but not completely nonlinear. (-; Computing the required frequencies should be simple: Nonlinear mixing creates the sum and the difference of the frequencies contained in the original signal, that is, if you want to play a sound with frequency f, then you need to find two frequencies a and b such that a-b = f (or b-a = f) and play "a" with one of the oscillators and "b" with the other. *How* that frequency is created doesn't really matter. So long Thomas Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 31, 2009 Author Share Posted July 31, 2009 Yeah, I didn't quite have the terminology right... I posted a sample in the other thread some time ago. I think I looked at the sound with my 'scope too... if you scrunch the waveform (visually), you see that it's approximating a triangle. Quote Link to comment Share on other sites More sharing options...
Bryan Posted July 31, 2009 Share Posted July 31, 2009 The triangles are created because the linear mid-point of an oscillating voice is not the voltage produced by two voice which are 180 degrees out of phase (canceling). Here's how to think of it: Amplitude 1: A PWM DAC allows the generation of any voltage between an ON voltage and an OFF voltage by varying the duty-cycle of a high-frequency (super-audible) signal. Usually the output is run through a low-pass filter. What remains is the average voltage. We cannot hear the oscillation frequency, but changes to the duty-cycle cause lower-frequency oscillations in the average voltage. A fast Pokey square wave will produce a simple 50-50 duty cycle PWM with a level half-way between the two states (50%). Two Pokey voices running in phase with each other will have the same effect. Amplitude 2: When two Pokey voices are running out of phase with each other, their output cancels producing a mid-point voltage determined by the output resistors (currents) in the two Pokey channels. Due to the nature of Pokey's volume control circuit, this voltage is not the true 50% point (this is called non-linearity) but is instead offset by some amount. Let's call it a 70% point for this discussion. Now, if two voices are set to run very fast (super-audible) but at slightly different frequencies, then we'll get the old phase-shift trick as the two channels add, then subtract from each other. However, because the frequency is very fast we will not hear them, but will instead hear the lower frequency shift from the PWM average (50%) to the cancellation average (70%) and back again. This creates a triangle, but at reduced volume. 1 Quote Link to comment Share on other sites More sharing options...
miker Posted August 6, 2009 Share Posted August 6, 2009 Thanks Rybags for getting busy with this problem. OK, tried something with it... Here's table with notes and corresponding values to be put in AUDF1 and AUDF3. Contains some "tradeoffs", because some notes tend to "whistle". note AUDF1 AUDF3 AUDF1(hex)AUDF3 ============================================================= C-3 37 38 25 26 C#3 52 54 34 36 D-3 50 52 32 34 D#3 33 34 21 22 E-3 47 49 2F 31 F-3 31 32 1F 20 F#3 44 46 2C 2E G-3 43 45 2B 2D G#3 51 54 33 36 A-3 40 42 28 2A A#3 48 51 30 33 H-3 46 49 2E 31 C-4 36 38 24 26 C#4 24 25 18 19 D-4 23 24 17 18 D#4 47 51 2F 33 E-4 46 50 2E 32 F-4 31 33 1F 21 F#4 48 53 30 35 G-4 41 45 29 2D G#4 45 50 2D 32 A-4 39 43 27 2B A#4 26 28 1A 1C H-4 45 51 2D 33 C-5 24 26 18 1A C#5 23 25 17 19 D-5 22 24 16 18 D#5 38 44 26 2C E-5 25 28 19 1C F-5 31 36 1F 24 F#5 32 38 20 26 G-5 24 28 18 1C G#5 22 26 16 1A A-5 20 24 14 18 A#5 20 25 14 19 H-5 19 25 13 19 And two small tests i've done in MPT (sampled to WAVs). Sorry for glitches. On real stuff it plays much-much cleaner. The PC-machine just listens "too carefully". triang.zip Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 6, 2009 Author Share Posted August 6, 2009 Nice. Do you have an XEX of that second one? From memory, on the real machine the low-pitched ones start to become undesirable when AUDF gets over the mid 60s or so. High pitched... of course we get the normal problem that the frequencies are spaced too far apart. Thing is though, we can live without the higher ones since they sound almost the same as square waves anyhow. Quote Link to comment Share on other sites More sharing options...
miker Posted August 6, 2009 Share Posted August 6, 2009 Not really xex files, but here's the atr with MPT and my trials (including small Ninja cover done by the way). Press "Ctrl+Tab" to go to menu and then "L" to load the music. triang.atr.zip Quote Link to comment Share on other sites More sharing options...
miker Posted August 6, 2009 Share Posted August 6, 2009 Well - not all tradeoffs made here are really good... G-4 note should consist of 51 and 57 (hex: 33 and 39) values instead of 41 and 45 (hex: 29 and 2D) as listed above, but then it may "whistle" so... Welcome bad note! but... Transposing whole song can help a bit. Quote Link to comment Share on other sites More sharing options...
emkay Posted August 6, 2009 Share Posted August 6, 2009 (edited) Interesting. It seems, POKEY still has more "SAW" features than the emulation can rebuild. The tune doesn't play anything "Sawtooth" like in the emulator. But your wavs seem to work. At least the emulation plays this sounds (an old mate for a reminder )... Btw. Sound precision. I realized that the emulation used in the SAP player somehow seems to be more accurate and sounding more like POKEY than the emulation used in the RMT and A8win+ . Eventhough many sounds do not work right now, the sounds the SAP plays (correctly) are more like the real hardware. Perhaps we should approach something like RMT SAP cooperation? aje2.zip Edited August 6, 2009 by emkay Quote Link to comment Share on other sites More sharing options...
miker Posted August 7, 2009 Share Posted August 7, 2009 Ok - made another WAV form that small Ninja cover. This time it plays cleaner. Removing some noiseusing Audacity did the job. Enjooy nice "tube" sound. Yeah, i wonder as well, when SAP/emulation could play these sounds. For "sawtooth" ones - they are more or less accurate played by ASAP 0.1.0 (but you make give it SAP file; can be made with RMT modified in any way). Also... Fox said that he contantly works on "new" features, so we can expect something new in ASAP "ASAP". ninja.zip Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 7, 2009 Author Share Posted August 7, 2009 Stupid question... how the hell do you get MPT to play the music once it's loaded... I've tried practically everything. Quote Link to comment Share on other sites More sharing options...
miker Posted August 7, 2009 Share Posted August 7, 2009 (edited) Oh, sorry, forgot... Exit menu by ESC, then press TAB if needed and once you are in patterns' window, press Ctrl+P and SPACE (to bring up the equalizer or any other key not to bring it up). The music will then play. Edited August 7, 2009 by miker Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 7, 2009 Author Share Posted August 7, 2009 Got it now. Don't suppose you've tried sawtooth? Or is it not supported by MPT. Quote Link to comment Share on other sites More sharing options...
miker Posted August 7, 2009 Share Posted August 7, 2009 Well - MPT can support sawtooth, but it will require another freq-table (only some first notes fit more or less). Ok, here's the atr updated with three more version's of Ninja (including this one sampled above) one of it uses sawtooth on table calculated above. triang.atr.zip Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 7, 2009 Author Share Posted August 7, 2009 I tried some sawtooth waves with the table I generated... I was sure the frequencies worked out the same way as triangles. Although I might have only tried adjacent AUDF values. Quote Link to comment Share on other sites More sharing options...
miker Posted August 7, 2009 Share Posted August 7, 2009 It seems also that sawtooth effect doesn't love greater value-differencies in AUDFs. Sometimes it just plays wrong octaves, but some notes are really "out-of-hell". Quote Link to comment Share on other sites More sharing options...
emkay Posted August 8, 2009 Share Posted August 8, 2009 A link may be useful at this point: http://www.atariage.com/forums/index.php?s...t&p=1414219 Quote Link to comment Share on other sites More sharing options...
analmux Posted August 21, 2009 Share Posted August 21, 2009 A link may be useful at this point: <a href="http://www.atariage.com/forums/index.php?s=&showtopic=116835&view=findpost&p=1414219" target="_self">http://www.atariage.com/forums/index.php?s...t&p=1414219</a> Thanks emkay. The link should now be http://www.atariage.com/forums/topic/116835-polycounter-reset-on-pokey/page__st__50__p__1414219entry1414219 Indeed, handling of sawtooth wave and triangle wave on pokey have much in common, see especially the following detail (also to be found in the post linked above): Note: in case of the sawtooth waveform the resulting frequency (expressed as 1.79mhz divided by an integer) is related to the l.c.m. (least common multiple) of both signal frequencies F1+4 and F3+4. In case of F1=F3+1 then it coincides with the simpson relation, so when pitchdifference is 1 notationtables for both sawtooth waveform and triangle waveform are the same. I've sorted this all out some time ago. ...thus to help you, miker, It seems also that sawtooth effect doesn't love greater value-differencies in AUDFs. Sometimes it just plays wrong octaves, but some notes are really "out-of-hell". We should be aware that the triangle wave is an interference effect, just by 'adding' two voice signals, with a slightly non-linear operation. When adding two periodic functions, and the two periods differ by a rational factor, we obtain another periodic function. The period/wavelenght of the resulting function is just the result of the famous 'Simpson rule'. For the sawtooth wave we are dealing with a different principle. The two signals won't get added, but rather 'multiplied', be it in a Boolean way. When the two periods are again differing by a rational factor, which is always the case, the resulting period/wavelength is the least common multiple of pitch1 and 3. We then have two situations: 1) the ratio is prime, i.e. the two pitches (+4) have no common prime divisors. In this case the least common multiple of pitch1 & 3 is just their ordinairy product. In this case the relation coincides with the Simpson rule (up to a factor 2). 2) the ratio is not prime. Then there are common prime divisors. In case pitch3=pitch1+1 they are always relatively prime. In case pitch3=pitch1+2 they are only relatively prime when pitch1 is odd. In case pitch3=pitch1+3 they are only relatively prime when pitch1 is not a multiple of 3...etc. ... In case pitch3=pitch1+6 they are only relatively prime when pitch1 is not a multiple of 2 or 3...etc. The more prime divisors pitch1 and 3 have in common, the more the resulting sound will differ from sawtooth. So, when trying pitch3=pitch1+30 will give some 'noises from hell' ...any more problems? Quote Link to comment Share on other sites More sharing options...
analmux Posted August 25, 2009 Share Posted August 25, 2009 ...What next? Well, it'd be nice to work out what's going on in two-tone mode. Maybe we could get some formulas and tables for doing variable pulsewidth square waves.More than a year ago I did some complete research for the 2-tone filter. Here's a picture which should be self-explaining. It's from part of my personal 'Pokey research diary'. Here F1 is just value in AUDF1 +1, F2 is AUDF2 +1. (asssuming 64 or 15 khz mode) The 2-tone filter at 1.79mhz and non-square distortions gives a whole jungle of weird instruments. 1 Quote Link to comment Share on other sites More sharing options...
dwhyte Posted August 26, 2009 Share Posted August 26, 2009 Awesome work analmux! Any chance of one day collecting all your successful research into a reference document? Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 26, 2009 Author Share Posted August 26, 2009 I think we need to revive the "Heavy Metal Atari" or whatever that document was called. We have all this sound stuff, Interlaced graphics, and all manner of other stuff that could go in there. Think of it as the "De Re" for the 21st Century. Quote Link to comment Share on other sites More sharing options...
dwhyte Posted August 26, 2009 Share Posted August 26, 2009 (edited) I think we need to revive the "Heavy Metal Atari" or whatever that document was called. We have all this sound stuff, Interlaced graphics, and all manner of other stuff that could go in there. Think of it as the "De Re" for the 21st Century. I concur. I'm not a tech writer though. My writing ability only extends to certain pulp fantasy novels that fill the bargain bins of Wal-Mart. Perhaps GoodByteXL could lend us his wordsmith skills on this matter? Edited August 26, 2009 by dwhyte Quote Link to comment Share on other sites More sharing options...
analmux Posted August 26, 2009 Share Posted August 26, 2009 Any chance of one day collecting all your successful research into a reference document?It's one of my wishes to have some time to make such a document. Most likely a .pdf generated from LaTeX, and some figures/pictures included. Of course some scope pictures of certain waveforms, f.e. Bryan's pictures of the squarewave which is not square, would be nice. Quote Link to comment Share on other sites More sharing options...
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