Client Side recording produces a silent file — TX audio is never captured (QsoRecorder::feedTxAudio has no signal connected)

[TnxQSO-Admin]

Report preparation

• I used the AI-assisted bug report tool (Help → Support → File an Issue)
• I have attached a support bundle or log file

What happened?

What happened

With record mode set to Client Side (recording stored on the PC), the resulting WAV file contains only a 44-byte header and zero audio samples. It is silent both in AetherSDR playback and in an external player (tested with Haruna).

With record mode set to Radio Side, the exact same recording works correctly and contains audio (both RX and TX).

This was observed during normal SSB/phone operation over a remote connection, where RX audio is heard normally through the client output device (Focusrite Scarlett 4i4). So decoded RX audio is definitely flowing through the client; the recording still ends up empty.

Environment

• OS: Linux (Arch / CachyOS, KDE)
• Connection: remote
• AetherSDR version: 26.5.2 (please confirm — this is the value in CLAUDE.md on main; replace with your actual build)
• Output device: Focusrite Scarlett 4i4 (RX monitor heard normally during the test)
• Note: the root cause appears to be a missing client-side signal connection and is expected to be independent of radio model, firmware, and OS.

Suggested fix

A read-only static investigation of the recording subsystem points to a single root cause: no audio source is ever connected to QsoRecorder::feedTxAudio, and during transmit there is no RX audio to fall back on.

Findings (file:line references from a read-only code read):

• QsoRecorder::feedTxAudio is declared (XXXQsoRecorder.hXXX) and implemented (XXXQsoRecorder.cppXXX) and is correctly designed: it calls float32ToInt16() on float32 input and writes to the WAV file.
• There is no connect() anywhere in the codebase that wires any signal to QsoRecorder::feedTxAudio. The slot is never called.
• The only signal wired to the recorder is RX audio:

connect(m_radioModel.panStream(), &PanadapterStream::audioDataReady,
        m_qsoRecorder, &QsoRecorder::feedRxAudio);

(in the MainWindow constructor). feedRxAudio only checks m_recording and m_file — no filtering.

• During transmit, the radio stops sending RX audio over the network, so audioDataReady carries silence. feedRxAudio writes nothing, feedTxAudio is never called, m_dataBytes stays 0, and patchWavHeader() writes a data size of 0 → valid 44-byte header, no samples.
• The only signal-based TX PCM tap, AudioEngine::txRawPcmReady, is emitted only when RADE digital mode is active (inside the m_radeMode block in XXXAudioEngine.cppXXX). For normal SSB/phone TX it never fires, so simply wiring txRawPcmReady → feedTxAudio would only fix TX recording in RADE mode, not SSB.
• The TX capture path that already works (the "Aetherial Audio" strip record button) does not use signals at all — it uses ClientPuduMonitor / m_finalMonitor via a direct atomic callback on the audio thread (the post-final-limiter monitor tap). This is the source that actually carries normal SSB TX/monitor audio in the client.
• Minor: the comment near the recorder connection in XXXMainWindow.cppXXX states that txRawPcmReady is int16 and would need separate handling. That comment is inaccurate — the signal carries float32, and feedTxAudio already converts float32 → int16. Worth correcting alongside the fix.

Fix direction (needs maintainer review per the architecture boundary in CLAUDE.md — this touches signal routing):

Route a TX PCM source into QsoRecorder so that Client Side recording captures TX. Because txRawPcmReady is RADE-only, the source that covers normal SSB is the same post-limiter monitor tap that the Aetherial Audio strip already uses successfully (ClientPuduMonitor / m_finalMonitor).

There is also a design decision for the maintainer: whether Client Side should write a single interleaved-in-time RX/TX file (matching Radio Side behavior, switching source on transmit state) or keep RX and TX handling explicit. I am not prescribing the exact wiring — flagging the root cause and the viable source.

Related

• Contest Support - Ability to record CW sidetone along with RX Audio. #2539 (Contest Support — record CW sidetone along with RX audio) touches the same recording subsystem but is a separate feature request about what is mixed into the recording, not this silent-file bug.

Suggested labels: bug, audio

What did you expect?

What I expected

The storage location must not change what gets recorded. Radio Side records both RX and TX into the file. Client Side should produce an equivalent recording — RX while receiving, my own TX (monitor) audio while transmitting — just written to local disk instead of the radio.

Steps to reproduce

Steps to reproduce

1. Connect to the radio remotely. Confirm RX audio is heard through the client output device.
2. Set record mode to Client Side (RadioSetupDialog → "Client Side").
3. Press the record button on the VfoWidget / panadapter.
4. Receive for a few seconds, then transmit (SSB) for a few seconds, then receive again.
5. Stop recording. Open the resulting WAV in AetherSDR or an external player.

Result: the file is 44 bytes (header only), no audio.

Repeat steps 2 to 5 with Radio Side selected. Result: the file contains audio (RX + TX).

AetherSDR version

v26.6.2

Radio model & firmware

AU-520 4.2.20.41343

Operating system

Linux

OS version and hardware

CachyOS

[aethersdr-agent]

Triage: confirmed bug. The static analysis in the report holds up against the source on main. Verified each claim:

Root cause (confirmed)

1. feedTxAudio is implemented and correct, but never wired. QsoRecorder::feedTxAudio (src/core/QsoRecorder.cpp:134-141) runs float32ToInt16() and writes to the WAV — it's fine. A repo-wide grep finds no connect() targeting QsoRecorder::feedTxAudio. The only feedTxAudio connection in the tree is for a different class, RADEEngine::feedTxAudio (src/gui/MainWindow_DigitalModes.cpp:316). So the QsoRecorder TX slot is dead.

2. Only RX is tapped. src/gui/MainWindow.cpp:1201-1202 wires PanadapterStream::audioDataReady → QsoRecorder::feedRxAudio and nothing else. feedRxAudio (QsoRecorder.cpp:125-132) only checks m_recording/m_file — no gating.

3. During TX the radio stops sending RX, so audioDataReady carries little/no audio, feedRxAudio writes ~nothing, feedTxAudio is never called, m_dataBytes stays 0, and patchWavHeader() (QsoRecorder.cpp:300-314) writes data size 0 → a valid 44-byte header with no samples. Matches the reported symptom exactly.

4. txRawPcmReady is RADE-only. It's emitted solely inside the if (m_radeMode) block at src/core/AudioEngine.cpp:4543. For normal SSB/phone TX it never fires, so wiring txRawPcmReady → feedTxAudio would fix RADE TX recording only, not SSB. Confirmed.

5. The working SSB TX source is the final-monitor tap. src/core/AudioEngine.cpp:4646-4648 feeds the post-limiter int16 stereo data to m_txFinalMonitor->feedTxPostDsp(data) on the audio thread, unconditional on mode. This is what the "Aetherial Audio" strip record button (ClientPuduMonitor / m_finalMonitor) already uses successfully for SSB monitor capture. That's the right source for normal-phone TX.

Extra detail for the fix

The stale comment is doubly wrong, and in a way that matters for implementation:

• src/gui/MainWindow.cpp:1199-1200 and the signal declaration at src/core/AudioEngine.h:497 both call txRawPcmReady int16. It actually carries float32 (emit txRawPcmReady(f32) at AudioEngine.cpp:4543), and feedTxAudio already expects float32. So the comment's stated reason for not wiring TX is incorrect.
• However, the recommended SSB source — the final-monitor tap (feedTxPostDsp) — is int16 (data at AudioEngine.cpp:4646), whereas feedTxAudio expects float32. So whichever route is chosen, a format/conversion step is required; it's just inverted from what the comment claims. The maintainer should pick one source and match the format, rather than connecting both blindly.

Proposed fix (needs maintainer decision — touches signal routing, per CLAUDE.md)

Route a TX PCM source into QsoRecorder for Client Side mode. Two sub-decisions for the maintainer:

1. Source: the post-limiter final-monitor tap (covers SSB + everything; int16, so add an int16-accepting feed on QsoRecorder or convert at the tap) is the only one that fixes normal phone. txRawPcmReady alone is insufficient (RADE-only).
2. File layout: whether Client Side writes a single interleaved-in-time RX/TX file (switch source on MOX, matching Radio Side) or keeps RX/TX explicit. If interleaving, gate feedRxAudio vs feedTxAudio on TX state so they don't both write (during TX, RX is already near-silent, but explicit gating via onMoxChanged is cleaner). QsoRecorder already tracks MOX (onMoxChanged, QsoRecorder.cpp:145-161), so the hook exists.

Also fix the two inaccurate int16 comments at MainWindow.cpp:1199-1200 and AudioEngine.h:497 alongside.

#2539 (CW sidetone in recordings) touches the same subsystem but is a separate feature, not this bug — agreed.

Handing to maintainer review. Not implementing in this pass.

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_{🤖 aethersdr-agent · cost: $1.7895 · model: claude-opus-4-8}

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_{📍 Citation health check (Foundry Constitution Principle I): 7 resolved, 7 unresolved against /Users/aetherclaude/workspace/AetherSDR at origin/main.}

Unresolved citations (7)

Citation	Reason
AudioEngine.cpp:4543	file not found in workspace
AudioEngine.cpp:4646	file not found in workspace
AudioEngine.h:497	file not found in workspace
MainWindow.cpp:1199-1200	file not found in workspace
QsoRecorder.cpp:125-132	file not found in workspace
QsoRecorder.cpp:145-161	file not found in workspace
QsoRecorder.cpp:300-314	file not found in workspace

[jensenpat]

I need logs to investigate this further.

[TnxQSO-Admin]

Of course @jensenpat, logs and file evidence below, plus a correction to my own report.

Correction: the "44-byte header" claim was wrong. I stated it as an observed result; it was a static-analysis inference and it does not hold. Measured, the client-side file is full length, not empty. It is full-length silence.

Recorder log (client-side recording, aether.audio raised to info level):

INF aether.audio: QsoRecorder: started recording to ".../2026-06-14_061708Z_7.188MHz_USB.wav"
INF aether.audio: QsoRecorder: stopped recording, 7 seconds, 696832 bytes

File on disk:

$ ls -l 2026-06-14_061708Z_7.188MHz_USB.wav

-rw-r--r-- 696876  2026-06-14_061708Z_7.188MHz_USB.wav

$ ffprobe -v error -show_entries format=size:stream=duration,sample_rate,channels 2026-06-14_061708Z_7.188MHz_USB.wav

[STREAM]
sample_rate=24000
channels=2
duration=7.258667
[/STREAM]
[FORMAT]
size=696876
[/FORMAT]

696876 = 696832 data + 44 header, and 24000 * 2ch * 2 bytes * 7.2587 s = 696832, so the recorder wrote a full-length stream during a transmit (SSB) recording. Loudness check confirms it is silent end to end:

$ ffmpeg -i 2026-06-14_061708Z_7.188MHz_USB.wav -af volumedetect -f null -
mean_volume: -91.0 dB
max_volume: -91.0 dB
histogram_91db: 348416

Every sample sits at the int16 noise floor. The file is full-length digital silence, not an empty/header-only file.

Corrected mechanism. feedRxAudio is the only source connected to the recorder (src/gui/MainWindow.cpp:1241-1242, audioDataReady -> feedRxAudio). It writes the full-length RX stream. During transmit that RX stream is muted, so the file is full-length silence. The operator TX audio is never captured, because QsoRecorder::feedTxAudio (src/core/QsoRecorder.cpp:134) has no connect() anywhere wiring a signal to it. The only feedTxAudio connection in the tree targets a different class, RADEEngine::feedTxAudio (src/gui/MainWindow_DigitalModes.cpp).

So the symptom is not an empty file; it is a full-length file carrying the wrong (muted-RX) source, with the operator TX source never tapped. A debug log cannot show the missing path directly, since the defect is an absent connection, so the file measurement plus the feedTxAudio grep are the concrete evidence.

The RADE-only txRawPcmReady tap (src/core/AudioEngine.cpp:4543, inside if (m_radeMode)) does not fire for SSB, so it is not the fix on its own. The source that already works for SSB TX monitor capture is the final-monitor tap (ClientPuduMonitor / m_finalMonitor, feedTxPostDsp), which is int16, so any wiring needs a format step. Leaving the source and file-layout choice to maintainer review per CLAUDE.md.

Full log attached (aethersdr-scrubbed.log), as requested.

The relevant lines are the two QsoRecorder entries (timestamps 08:17:08 to 08:17:15), captured with aether.audio raised to info level via:

QT_LOGGING_RULES="aether.audio.info=true;aether.audio.debug=true"

INF aether.audio: QsoRecorder: started recording to ".../2026-06-14_061708Z_7.188MHz_USB.wav"
INF aether.audio: QsoRecorder: stopped recording, 7 seconds, 696832 bytes

The rest of the log is unrelated tuning and UI activity. As noted above, a log cannot show the root cause directly: the defect is a missing connect() to QsoRecorder::feedTxAudio, so there is no code path to trace. The recorder simply ran for 7 seconds writing the muted-RX stream (full-length silence, confirmed by the volumedetect measurement) and the operator TX audio was never tapped. The file measurement and the feedTxAudio grep remain the decisive evidence; the log just confirms the recorder started and stopped cleanly with a non-zero byte count.

aethersdr-scrubbed.log