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| strokeanalysis:stroke_analysis [2013/02/03 19:16] – [Conclusion] deva | strokeanalysis:stroke_analysis [2013/02/21 12:35] (current) – deva | ||
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| Two types of analysis are performed: | Two types of analysis are performed: | ||
| * A single hard kick drum stroke. | * A single hard kick drum stroke. | ||
| - | * A series of strokes at high tempo. | + | * A series of strokes at relatively |
| These two types of strokes are the result of very different playing styles and should cover the most basic uses of the kick drum in metal music. | These two types of strokes are the result of very different playing styles and should cover the most basic uses of the kick drum in metal music. | ||
| - | The experiment was performed on an Axis Longboard pedal only, but should for good measure be performed on other types of pedals too. | + | The experiment was performed on an Axis Longboard pedal only, but should for good measure be performed on other types of pedals too sometime in the future... |
| - | A movie was made with 200fps | + | A movie was recorded |
| {{: | {{: | ||
| {{: | {{: | ||
| {{: | {{: | ||
| {{: | {{: | ||
| - | Note the white dots on the center-of-axis as well on the mallet. These were added in order to be able to identify | + | Note the white dots on the center-of-axis as well on the mallet. These were added in order to be able to identify |
| - | + | ||
| - | + | ||
| - | ====Single stroke==== | + | |
| - | ^ Position ^ Vector | + | |
| - | | 0 | (-255,391) | 466.80px | 0.000000 | + | |
| - | | 1 | (-247,394) | 465.02px | 1.027597 | + | |
| - | | 2 | (-235,405) | 468.24px | 2.987024 | + | |
| - | | 3 | (-210,420) | 469.57px | 6.546291 | + | |
| - | | 4 | (-176,440) | 473.89px | 11.309932 | 4.763642 | + | |
| - | | 5 | (-134,458) | 477.20px | 16.803111 | 5.493178 | + | |
| - | | 6 | ( -74,480) | 485.67px | 24.347241 | 7.544131 | + | |
| - | | 7 | ( -6,491) | 491.04px | 32.411225 | 8.063984 | + | |
| - | | 8 | ( 73,493) | 498.38px | 41.534099 | 9.122874 | + | |
| - | | 9 | ( 146,480) | 501.71px | 50.029355 | 8.495256 | + | |
| - | | 10 | ( 232,451) | 507.17px | 60.333194 | 10.303839 | + | |
| - | | 11 | ( 240,446) | 506.47px | 61.396774 | 1.063580 | + | |
| - | | 12 | ( 229,452) | 506.70px | 59.979810 | -1.416964 | + | |
| + | ====Meaurements==== | ||
| + | ===Single stroke=== | ||
| + | ^ Position ^ Vector | ||
| + | | 0 | (-255,391) | 466.80 | 0.00 | 0.00 | 0.00 | | ||
| + | | 1 | (-247,394) | 465.02 | 1.03 | 1.03 | 226.07 | | ||
| + | | 2 | (-235,405) | 468.24 | 2.99 | 1.96 | 431.07 | | ||
| + | | 3 | (-210,420) | 469.57 | 6.55 | 3.56 | 783.04 | | ||
| + | | 4 | (-176,440) | 473.89 | 11.31 | 4.76 | 1048.00 | | ||
| + | | 5 | (-134,458) | 477.20 | 16.80 | 5.49 | 1208.50 | | ||
| + | | 6 | (-74,480) | 485.67 | 24.35 | 7.54 | 1659.71 | | ||
| + | | 7 | (-6,491) | 491.04 | 32.41 | 8.06 | 1774.08 | | ||
| + | | 8 | (73,493) | 498.38 | 41.53 | 9.12 | 2007.03 | | ||
| + | | 9 | (146,480) | 501.71 | 50.03 | 8.50 | 1868.96 | | ||
| + | | 10 | (232,451) | 507.17 | 60.33 | 10.30 | 2266.84 | | ||
| + | | 11 | (240,446) | 506.47 | 61.40 | 1.06 | 233.99 | | ||
| + | | 12 | (229,452) | 506.70 | 59.98 | -1.42 | -311.73 | | ||
| A plot of the angle velocities reveal a rather ' | A plot of the angle velocities reveal a rather ' | ||
| {{: | {{: | ||
| - | ====Stroke sequence==== | + | ===Stroke sequence=== |
| - | ^ Position ^ Vector | + | ^ Position ^ Vector |
| - | | 0 | (-381,215) | 437.48px | 0.000000 | + | | 0 | (-255,391) | 466.80 | 0.000000 |
| - | | 1 | (-370,236) | 438.86px | 3.095041 | + | | 1 | (-247,394) | 465.02 | 1.027597 |
| - | | 2 | (-356,267) | 445.00px | 7.433667 | + | | 2 | (-235,405) | 468.24 | 2.987024 |
| - | | 3 | (-331,304) | 449.42px | 13.129037 | + | | 3 | (-210,420) | 469.57 | 6.546291 |
| - | | 4 | (-298,346) | 456.64px | 19.826380 | + | | 4 | (-176,440) | 473.89 | 11.309932 |
| - | | 5 | (-255,389) | 465.13px | 27.317846 | + | | 5 | (-134,458) | 477.20 | 16.803111 |
| - | | 6 | (-203,425) | 470.99px | 35.032433 | + | | 6 | ( -74,480) | 485.67 | 24.347241 |
| - | | 7 | (-144,458) | 480.10px | 43.110075 | + | | 7 | ( -6,491) | 491.04 | 32.411225 |
| - | | 8 | ( -78,483) | 489.26px | 51.390233 | + | | 8 | ( 73,493) | 498.38 | 41.534099 |
| - | | 9 | ( -14,494) | 494.20px | 58.940436 | + | | 9 | ( 146,480) | 501.71 | 50.029355 |
| - | | 10 | ( 54,496) | 498.93px | 66.777144 | + | | 10 | ( 232,451) | 507.17 | 60.333194 |
| - | | 11 | ( 110,492) | 504.15px | 73.166538 | + | | 11 | ( 240,446) | 506.47 | 61.396774 |
| - | | 12 | ( 162,483) | 509.44px | 79.105414 | 5.938875 | + | | 12 | ( 229,452) | 506.70 | 59.979810 |
| - | | 13 | ( 198,468) | 508.16px | 83.495869 | 4.390456 | + | |
| - | | 14 | ( 216,464) | 511.81px | 85.526559 | 2.030689 | + | |
| - | | 15 | ( 210,467) | 512.04px | 84.776208 | + | |
| The graph of these angle velocities show a picture rather more ' | The graph of these angle velocities show a picture rather more ' | ||
| {{: | {{: | ||
| Line 60: | Line 56: | ||
| ====Evaluation===== | ====Evaluation===== | ||
| ===Samplerate=== | ===Samplerate=== | ||
| - | The maximum angle velocity was found in the single stroke and was 2061 degrees per second. | + | The maximum angle velocity was found in the single stroke and was 2266.84 |
| That the maximum angle velocity should be found in the stroke type is not surprising since a single stroke is the result of the hardest foot impact on the pedal.\\ | That the maximum angle velocity should be found in the stroke type is not surprising since a single stroke is the result of the hardest foot impact on the pedal.\\ | ||
| - | If we assume the target latency to be at most 1ms and we assume that the software is responding in the area of microseconds we can estimate the target ADC resolution.\\ | + | If we assume the target latency to be at most 1ms and we assume that the software is responding in the area of microseconds |
| - | Lets start by pointing out that since the video framerate was 200fps | + | Lets start by pointing out that since the video framerate was 220fps |
| - | The single stroke took 11 frames in total which is 55ms and during this time the mallet moved 61.4 degrees, resulting in a minimum resolution of 1.12 samplings per millisecond. | + | The single stroke took 11 frames in total which is 50ms and during this time the mallet moved 61.4 degrees, resulting in a minimum resolution of 1.23 samplings per millisecond. |
| - | However, if we look at the diff in the last two velocities before the impact it was 10.3 degrees in 5ms it is evident that the minimum resolution should be higher, namely 2.06 samplings per millisecond. | + | However, if we look at the diff in the last two velocities before the impact it was 10.3 degrees in 4.55ms |
| - | Ergo: **A sampling of 2kHz should be sufficient.** | + | Ergo: **A sampling of approximately |
| - | //However// ... the result of this mechanism is the playing of a sample at probably 44.1kHz or 48kHz and in order to avoid phasing problems when mixing with the analogue | + | //However// ... the result of this mechanism is the playing of a sample at probably 44.1kHz or 48kHz and in order to avoid phasing problems when mixing with the analogue |
| ===Bit precision=== | ===Bit precision=== | ||
| - | Lets again look at the highest | + | When considering bit precision it is the lowest |
| + | If we therefore look at the stroke sequence we can observe a 2.03 degrees | ||
| + | If we divide the entire 84 degree interval into 0.446 degree segments the result is a minimum of 188 steps. | ||
| - | Between the last two frames (5ms) there are an angle diff of 10.3 degrees, ie. 2.06 degrees in the last millisecond before impact. | + | Ergo: **A bit precision |
| - | If we divide the entire 84 degree (maximum angle span observed in the stroke sequence, not the single stroke) interval into 2.06 degree segments the result is a minimum of 40 steps. | + | |
| - | Ergo: **A bit precision of 6 should be sufficient.** | + | //However// ... since we cannot assume that we will work within the entirety of the bit span of the ADC it should be noted that the 8 bit precision is the //used// number of bits for the mallet swing and a substantial amount of headroom should be added in order to match different spring types and initial |
| - | + | ||
| - | //However// ... since we cannot assume that we will work within the entirety of the bit span of the ADC it should be noted that the 6 bit precision is the //used// number of bits for the mallet swing and a substantial amount of headroom should be added in order to match different spring types and tensions. | + | |
| How much ' | How much ' | ||
| Line 88: | Line 83: | ||
| Since this experiment has not been performed by the fastest or hardest hitting drummer in the world, or the most latency sensitive one for that matter, we should increase both samplerate and bit precision in order to make sure all drummers are covered. | Since this experiment has not been performed by the fastest or hardest hitting drummer in the world, or the most latency sensitive one for that matter, we should increase both samplerate and bit precision in order to make sure all drummers are covered. | ||
| - | If say the drummer hits twice as hard (double the angle velocity) and cannot accept latency at more than 0.1ms the calculations from above will be:\\ | + | If say the drummer hits twice as hard (double the angle velocity) and cannot accept latency at more than 0.5ms the calculations from above will be:\\ |
| + | |||
| + | Samplerate: 2 * 2.03 degrees in 4.55ms = **8kHz sampling** (but still it should be considered to use 44.1kHz or 48kHz to avoid phasing problems)\\ | ||
| - | Samplerate: 20.6 degrees in 5ms = 4kHz sampling (still | + | A very slow stroke is the worst case scenario when considering |
| + | If say the angle velocity is half of the measured one and the drummer is sensitive | ||
| - | Bit precision: | + | Bit precision: |
