From 2814aaedd1fa69ad83206008a05ddb5282700953 Mon Sep 17 00:00:00 2001
From: ANDROIDHASSAN <84630851+ANDROIDHASSAN@users.noreply.github.com>
Date: Thu, 12 Nov 2026 19:37:18 +0530
Subject: [PATCH] fix(rtc): return no frames from AudioResampler.flush() when
 nothing is buffered

The FFI flush reply carries a non-zero output_ptr with size 0 when the resampler has no data left, so the ptr check never matched and flush() returned one 0-sample frame. Check the size instead, as the docstring promises an empty list.
---
 .changeset/resampler-flush-empty.md        | 5 +++++
 livekit-rtc/livekit/rtc/audio_resampler.py | 2 +-
 tests/rtc/test_resampler.py                | 9 +++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/resampler-flush-empty.md

diff --git a/.changeset/resampler-flush-empty.md b/.changeset/resampler-flush-empty.md
new file mode 100644
index 000000000..3d2d57018
--- /dev/null
+++ b/.changeset/resampler-flush-empty.md
@@ -0,0 +1,5 @@
+---
+"livekit-rtc": patch
+---
+
+Return no frames from `AudioResampler.flush()` when nothing is buffered, instead of one empty frame.
diff --git a/livekit-rtc/livekit/rtc/audio_resampler.py b/livekit-rtc/livekit/rtc/audio_resampler.py
index 4d4c02c52..b9ef74635 100644
--- a/livekit-rtc/livekit/rtc/audio_resampler.py
+++ b/livekit-rtc/livekit/rtc/audio_resampler.py
@@ -142,7 +142,7 @@ def flush(self) -> list[AudioFrame]:
 
         resp = FfiClient.instance.request(req)
 
-        if not resp.flush_sox_resampler.output_ptr:
+        if not resp.flush_sox_resampler.size:
             return []
 
         cdata = (ctypes.c_int8 * resp.flush_sox_resampler.size).from_address(
diff --git a/tests/rtc/test_resampler.py b/tests/rtc/test_resampler.py
index db05c4fd1..4261e73c0 100644
--- a/tests/rtc/test_resampler.py
+++ b/tests/rtc/test_resampler.py
@@ -65,3 +65,12 @@ def test_audio_resampler() -> None:
             wf_out.setsampwidth(sampwidth)
             wf_out.setframerate(8000)
             wf_out.writeframes(output_data)
+
+
+def test_flush_with_nothing_buffered_returns_no_frames() -> None:
+    resampler = AudioResampler(48000, 16000)
+    assert resampler.flush() == []
+
+    resampler.push(AudioFrame(bytes(9600), 48000, 1, 4800))
+    assert sum(f.samples_per_channel for f in resampler.flush()) > 0  # the buffered tail
+    assert resampler.flush() == []