Summary

The float32 audio pipeline migration (502b934, b0c49d7) missed the macOS VirtualAudioBridge and the PCC_IF_NARROW DAX path in PanadapterStream, causing severe audio corruption on the macOS DAX virtual sound card. Digital mode software (VARA HF, WSJT-X) connected via the AetherSDR DAX device sees the audio spectrum displaced from the expected ~1500 Hz center frequency, making modems unable to decode signals.

Root Cause

After the float32 migration, PanadapterStream::daxAudioReady emits float32 stereo PCM. All downstream consumers were updated accordingly — TciServer::onDaxAudioReady, RADEEngine::feedRxAudio, and the Linux PipeWireAudioBridge (3400133) — but the macOS VirtualAudioBridge::feedDaxAudio() was not. It still reinterpret_cast's the incoming QByteArray as int16_t* and divides by 32768.0f:

// Before (broken): reads float32 bytes as int16
const auto* samples = reinterpret_cast<const int16_t*>(pcm.constData());
const float scale = chGain / 32768.0f;
block->ringBuffer[wp % RING_SIZE] = samples[i] * scale;

When float32 samples (4 bytes each) are reinterpreted as int16 (2 bytes each), every sample value is completely wrong — the ring buffer is filled with garbage, and the HAL plugin outputs corrupted audio to VARA/WSJT-X.

Additionally, PanadapterStream's PCC_IF_NARROW path (full-bandwidth stereo DAX) was still converting radio float32 → int16 via qBound(-1.0f, f, 1.0f) * 32767.0f before emission. This was missed by b0c49d7 which only fixed PCC_IF_NARROW_REDUCED. The lossy int16 conversion (clamping to ±1.0) combined with the format mismatch in VirtualAudioBridge compounded the corruption.

Fix

• VirtualAudioBridge::feedDaxAudio(): Read payload as float*, compute sample count by dividing by sizeof(float), multiply by chGain directly (no /32768 normalization). Update RMS meter to operate on float samples natively.
• PanadapterStream PCC_IF_NARROW path: Emit native float32 stereo (memcpy from big-endian-swapped uint32 to float) instead of converting to int16. Now consistent with PCC_IF_NARROW_REDUCED and all downstream consumers.
• Info.plist.in: Add NSLocalNetworkUsageDescription — required by macOS for UDP broadcast discovery of FlexRadio devices on port 4992. Without this key, the radio does not appear in the device list.

Test plan

• Build on macOS (ARM64, Qt 6.11)
• Connect to FLEX-8600 (FW 1.4.0.0) in DIGU mode with DAX enabled
• Verify VARA HF v4.9.0 receives audio spectrum correctly centered at ~1500 Hz via AetherSDR DAX virtual sound card
• Verify radio appears in device list on macOS (NSLocalNetworkUsageDescription)

🤖 Generated with Claude Code