NVGate DSP computation SPU

Force DSP

On force DSP (and normal DSP), the number of SPU change according to the max sampling frequency.

The more you have data to analyse (high sampling frequency), the less you have power computation (SPU). We have:

Sampling Frequency (kHz)	Number of SPU / DSP (Normal or Force)
102.4	6
65.536	9
51.2	12
32.768	18
25.6	24
16.384	36
12.8	48
6.4	96
3.2	192
1.6	384

FFT

According to the architecture of force DSP, the SPU computation per channels is not linear. So we have the following table for real time SPU computation :

Number of FFT lines	Normal DSP: SPU / channel	Force DSP: SPU / channel
401	1	0.33
801	1.25	0.18 (yes1)
1601	1.5	0.75
3201	2	0.8
6401	3	2
12801	4	2
25601	6	3.5

Envelope: 401 lines : 2 SPU per channel on force DSP

Zoom: 401 Lines : 0.66 SPU per channel on force DSP.

1) Computing is not linear and FFT 801 lines is the most optimised for DSP

Recorder

Recorder Sampling frequency (Hz)	Normal DSP: SPU / channel	Force DSP: SPU / channel
51200 or upper	1	0.66
32768	0.66	0.44
25600	0.5	0.33
16384	0.33	0.22
12800	0.25	0.167
Else	0.125	0.083

Octave

Octave	Normal DSP: SPU / channel	Force DSP: SPU / channel
1/3	3	1
1/12	6	2
1/24	12	4

OVA

Normal DSP: SPU / channel	Force DSP: SPU / channel
1	0.25

TDA

Normal DSP: SPU / channel	Force DSP: SPU / channel
3	1.5

SOA

SPU computation for SOA is more complex because it depends of maximum speed, resolution and frequency. Also force DSP computation is not linear.

Force DSP will improve the SPU computation by reducing between 2.5 and 5 to compare with normal DSP.

(@20kHz - 401 lines, we need a maximum of 3 SPUs with normal DSP)

Normal DSP

SPU computation for normal DSP : OR34 V1 - OR35V1 - OR36V1 OR36V2 (normal DSP) - OR38V1 - OR38V2 (Normal DSP).

Because of the computation linearity, we simplify by saying: 1DSP = 12 SPU (no matter the sampling frequency). This allow a simplification for SPU computation. So we can deduce:

FFT

Computation SPUs:

Bandwidth	Fdec	Resolution	Envelope	Zoom	SPU/Channel for Real-time	SPU/Channel for non Real-time
20k	1	401	No	No	1	0,5
10k	1	401	No	No	0,5	0,25
Nk	1	401	No	No	=N/20	=N/40
10k	2	401	No	No	1	1
5k	4	401	No	No	0,8	0,6
2k	10	401	No	No	0,6	0,6
1k	20	401	No	No	0,5	0,6
Lower than 1k	Higher than 20	401	No	No	0,5	0,5
20k	1	401 and below	No	No	1	0,5
20k	1	801	No	No	1,25	0,5
20k	1	1601	No	No	1,5	0,5
20k	1	3201	No	No	2	0,5
20k	1	6401	No	No	3	0,5
20k	1	401	No	No	1	0,5
20k	1	401	No	Yes	2	1,5
20k	1	401	No	No	1	0,5
20k	1	401	Yes	Yes	3	3

SOA

Computation SPUs:

Bandwidth (Hz)	Decimation factor	Resolution	SPU/Channel
20 k	1	401	3
10 k	1	401	1,5
N k	1	401	=(N*3)/20
10 k	2	401	2
5 k	4	401	1,3
2,5 k	8	401	1,1
1,25 k	16	401	0,9
625	32	401	0,8
313	64	401	0,7
156	128	401	0,6
78	256	401	0,6
20 k	1	401 and below	3
20 k	1	801	3,25

Sampling Frequency: set in Front-End/Inputs settings/Input sampling

FFT Bandwidth: set in FFTx/FFT analysis/range

==

Octave:

Bandwidth	Fdec	Reso	SPU/Channel for Real-time
25.6k	1	1/3rd	4
20k	1	1/3rd	3
12.8k	1	1/3rd	2
10k	1	1/3rd	1,5
20k	1	1/3rd	3,0
10k	2	1/3rd	2,0
5k	4	1/3rd	1,25
20k	1	1/1	1,5
20k	1	1/3rd	3
20k	1	1/12th	6
20k	1	1/24th	12

Sampling Frequency: set in Front-End/Inputs settings/Input sampling

1/N Oct Bandwidth: set in OCT/FFT analysis/range

OVA

Bandwidth	SPU/Channel for Real-time
25,6k	1,25
20k	1
12,8k	0,75
10k	0,5

The overall acoustic levels analysis requires 1 SPU per channel at 20 kHz bandwidth. The number of required SPUs is directly proportional to the analysis bandwidth (i.e. the sampling frequency divided by 2.56).