DSD sources

DSD heritage in PCM

Some DSD-to-PCM transfers retain a noise rise beyond audible frequencies. This analysis searches for that shape in high-rate PCM files.

Reading the result

The Hi-Res (DSD source) badge describes a shape consistent with that transfer. Another process can produce the same shape; filtering can remove it.

Illustrative spectrum without a measurement scale. Different processes can produce the same shape; see the analysis limits.

Go deeperMethod, limits, verification and sources

This analysis recognises a spectral shape associated with a DSD master converted to high-resolution PCM. It is used as evidence for the descriptive Hi-Res (DSD source) badge; it does not create an authenticity warning and does not prove that the PCM file came from DSD.

Calculation#

The check runs only on PCM at 96 kHz or above, using the averaged spectrum from the normal streaming analyzer. It measures a valley from 22–30 kHz and an ultrasonic ramp from 36 kHz to the lower of 75 kHz or 92% of Nyquist. The detector returns a result when both conditions hold:

Requirement	Threshold
Ultrasonic rise	Ramp minus valley at least 15 dB
Absolute ramp level	Above −75 dB relative to the spectral peak

Both bands must span enough finite FFT bins. The wide-band average is intentional: it avoids turning a few isolated high-frequency bins into a source claim.

Interpretation and limits#

DSD's sigma-delta process can create an ultrasonic noise ramp that remains when a DSD master is converted to a sufficiently high-rate PCM file. The test looks for that shape. It cannot distinguish a real DSD transfer from another process that produces the same spectral valley and rise, and it can miss a DSD transfer after low-pass filtering, noise reduction or later processing.

A missing result is not evidence that a high-resolution PCM master is native PCM. It says only that the defined ramp was not established. The corresponding DSD-file check is separate: see DSD PCM-source detection.

Tests#

cargo test -p flaccompagnon-core dsd::spectral
cargo test -p flaccompagnon-core pipeline

For a practical check, import a documented high-rate PCM transfer of DSD material and inspect its spectrum alongside the result. Do not use the badge as a provenance certificate.

Integrating the engine in your software?

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