NVGate DSP computation SPU
💡 Key principle: The higher the sampling frequency, the more data to process — and the fewer SPUs are available per DSP board. SPU budget must be shared across all active channels and analysis types.
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🔵 Normal DSP
Models: OR34 V1 · OR35 V1 · OR36 V1/V2 · OR38 V1/V2
Computation is linear: 1 DSP = 12 SPU, regardless of sampling frequency. |
🟠 Force DSP
SPU count varies with sampling frequency. Higher frequency = fewer available SPUs. Force DSP generally requires 2.5× to 5× fewer SPUs per channel than Normal DSP.
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📊 SPU Availability vs. Sampling Frequency
Applies to both Force DSP and Normal DSP modes.
| Sampling Frequency (kHz) | SPU per DSP board |
|---|---|
| 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 |
{{#widget:CalculateurSPU}}
🔬 FFT
⚠️ Force DSP note: Computation is not linear. FFT 801 lines is the most optimised configuration. Envelope (401 lines) = 2 SPU/ch · Zoom (401 lines) = 0.66 SPU/ch.
| FFT Lines | 🔵 Normal DSP (SPU/ch) | 🟠 Force DSP (SPU/ch) |
|---|---|---|
| 401 | 1 | 0.33 |
| 801 | 1.25 | 0.18 ① |
| 1 601 | 1.5 | 0.75 |
| 3 201 | 2 | 0.8 |
| 6 401 | 3 | 2 |
| 12 801 | 4 | 2 |
| 25 601 | 6 | 3.5 |
① 801 lines is the most optimised resolution for Force DSP.
🔵 Normal DSP — bandwidth & options effect (401 lines, Fdec=1 as base)
| Bandwidth | Fdec | Resolution | Envelope | Zoom | SPU/ch (real-time) | SPU/ch (non real-time) |
|---|---|---|---|---|---|---|
| 20 kHz | 1 | 401 | No | No | 1 | 0.5 |
| 10 kHz | 1 | 401 | No | No | 0.5 | 0.25 |
| N kHz | 1 | 401 | No | No | = N/20 | = N/40 |
| 10 kHz | 2 | 401 | No | No | 1 | 1 |
| 5 kHz | 4 | 401 | No | No | 0.8 | 0.6 |
| 2 kHz | 10 | 401 | No | No | 0.6 | 0.6 |
| 1 kHz | 20 | 401 | No | No | 0.5 | 0.6 |
| < 1 kHz | > 20 | 401 | No | No | 0.5 | 0.5 |
| 20 kHz | 1 | 801 | No | No | 1.25 | 0.5 |
| 20 kHz | 1 | 1 601 | No | No | 1.5 | 0.5 |
| 20 kHz | 1 | 3 201 | No | No | 2 | 0.5 |
| 20 kHz | 1 | 6 401 | No | No | 3 | 0.5 |
| 20 kHz | 1 | 401 | No | Yes | 2 | 1.5 |
| 20 kHz | 1 | 401 | Yes | Yes | 3 | 3 |
🎙️ Recorder
Force DSP only.
| Recorder Sampling Frequency (Hz) | 🔵 Normal DSP (SPU/ch) | 🟠 Force DSP (SPU/ch) |
|---|---|---|
| ≥ 51 200 | 1 | 0.66 |
| 32 768 | 0.66 | 0.44 |
| 25 600 | 0.5 | 0.33 |
| 16 384 | 0.33 | 0.22 |
| 12 800 | 0.25 | 0.167 |
| Other | 0.125 | 0.083 |
🎵 Octave
Force DSP — summary:
| Resolution | 🔵 Normal DSP (SPU/ch) | 🟠 Force DSP (SPU/ch) |
|---|---|---|
| 1/3 oct | 3 | 1 |
| 1/12 oct | 6 | 2 |
| 1/24 oct | 12 | 4 |
Normal DSP — full detail:
| Bandwidth | Fdec | Resolution | SPU/ch (real-time) |
|---|---|---|---|
| 25.6 kHz | 1 | 1/3 oct | 4 |
| 20 kHz | 1 | 1/3 oct | 3 |
| 12.8 kHz | 1 | 1/3 oct | 2 |
| 10 kHz | 1 | 1/3 oct | 1.5 |
| 10 kHz | 2 | 1/3 oct | 2 |
| 5 kHz | 4 | 1/3 oct | 1.25 |
| 20 kHz | 1 | 1/1 oct | 1.5 |
| 20 kHz | 1 | 1/12 oct | 6 |
| 20 kHz | 1 | 1/24 oct | 12 |
Sampling Frequency: Front-End / Inputs settings / Input sampling · Bandwidth: OCT / FFT analysis / range
📈 OVA (Overall Acoustic Levels)
Force DSP:
| 🔵 Normal DSP (SPU/ch) | 🟠 Force DSP (SPU/ch) |
|---|---|
| 1 | 0.25 |
Normal DSP — by bandwidth:
| Bandwidth | SPU/ch (real-time) |
|---|---|
| 25.6 kHz | 1.25 |
| 20 kHz | 1 |
| 12.8 kHz | 0.75 |
| 10 kHz | 0.5 |
SPU count is directly proportional to analysis bandwidth (sampling frequency ÷ 2.56).
⏱️ TDA
| 🔵 Normal DSP (SPU/ch) | 🟠 Force DSP (SPU/ch) |
|---|---|
| 3 | 1.5 |
🔄 SOA (Order Analysis)
⚠️ SOA computation depends on maximum speed, resolution and frequency. Force DSP computation is non-linear and reduces SPU consumption by 2.5× to 5× vs Normal DSP.
Example: @20 kHz, 401 lines → max 3 SPU/ch with Normal DSP.
Normal DSP — SOA detail:
| Bandwidth (Hz) | Decimation | Resolution | SPU/ch |
|---|---|---|---|
| 20 kHz | 1 | 401 | 3 |
| 10 kHz | 1 | 401 | 1.5 |
| N kHz | 1 | 401 | = (N × 3) / 20 |
| 10 kHz | 2 | 401 | 2 |
| 5 kHz | 4 | 401 | 1.3 |
| 2.5 kHz | 8 | 401 | 1.1 |
| 1.25 kHz | 16 | 401 | 0.9 |
| 625 Hz | 32 | 401 | 0.8 |
| 313 Hz | 64 | 401 | 0.7 |
| 156 Hz | 128 | 401 | 0.6 |
| 78 Hz | 256 | 401 | 0.6 |
| 20 kHz | 1 | 801 | 3.25 |
Sampling Frequency: Front-End / Inputs settings / Input sampling · FFT Bandwidth: FFTx / FFT analysis / range
