From d425f4a83f8bdfe188fc6920209b54ced91db6d7 Mon Sep 17 00:00:00 2001
From: Sebastian Mohr <sebastian@mohrenclan.de>
Date: Wed, 7 Jan 2026 16:52:29 +0100
Subject: [PATCH 1/3] Depending on python version and hardware the
 `DEFAULT_BUFFER_SIZE` which we use to ingest/feed in fingerprinting can
 influence the generated fingerprints.

This fixes the issue by only consuming the expected samples.
---
 acoustid.py | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/acoustid.py b/acoustid.py
index b7e66cb..ccab5c4 100644
--- a/acoustid.py
+++ b/acoustid.py
@@ -221,13 +221,21 @@ def fingerprint(samplerate, channels, pcmiter, maxlength=MAX_AUDIO_LENGTH):
         fper = chromaprint.Fingerprinter()
         fper.start(samplerate, channels)
 
-        position = 0  # Samples of audio fed to the fingerprinter.
-        for block in pcmiter:
-            fper.feed(block)
-            position += len(block) // 2  # 2 bytes/sample.
-            if position >= endposition:
+        position = 0
+        while position < endposition:
+            try:
+                block = next(pcmiter)
+            except StopIteration:
+                # No more data
                 break
 
+            # Calculate remaining samples needed
+            remaining = endposition - position
+            # Feed only up to remaining samples
+            bytes_to_feed = min(len(block), remaining * 2)
+            fper.feed(block[:bytes_to_feed])
+            position += bytes_to_feed // 2
+
         return fper.finish()
     except chromaprint.FingerprintError:
         raise FingerprintGenerationError("fingerprint calculation failed")

From 01a5af00017fef1907bbc2b30fd0a417d8ebd68d Mon Sep 17 00:00:00 2001
From: Sebastian Mohr <sebastian@mohrenclan.de>
Date: Thu, 9 Apr 2026 15:18:17 +0200
Subject: [PATCH 2/3] Added a test which shows allows to reproduce the issue.

---
 test/test_acoustid.py | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/test/test_acoustid.py b/test/test_acoustid.py
index 79b1a1e..3cd16b4 100644
--- a/test/test_acoustid.py
+++ b/test/test_acoustid.py
@@ -257,6 +257,46 @@ def raise_error(*_):
         with pytest.raises(acoustid.FingerprintGenerationError):
             acoustid.fingerprint(44100, 2, [b"\x00\x00"])
 
+    @pytest.mark.parametrize(
+        "block_sizes",
+        [
+            (2, 4),
+        ],
+    )
+    def test_fingerprint_inconsistent_block_sizes(
+        self, monkeypatch, block_sizes: list[int]
+    ):
+        """Different block sizes may produce inconsistent results."""
+        from unittest.mock import Mock
+
+        def chunk_by_size(lst, size):
+            for i in range(0, len(lst), size):
+                yield lst[i : i + size]
+
+        data = bytes(range(100))  # b'\x00\x01\x02...\x63'
+
+        monkeypatch.setattr("chromaprint.Fingerprinter.start", Mock())
+        monkeypatch.setattr("chromaprint.Fingerprinter.finish", Mock())
+
+        values = []
+        for b in block_sizes:
+            mock = Mock()
+            monkeypatch.setattr("chromaprint.Fingerprinter.feed", mock)
+
+            acoustid.fingerprint(
+                1,
+                1,
+                chunk_by_size(data, b),
+                5,
+                # Half the block is consumed -> 5*2 = 10
+            )
+
+            flattened_bytes = b"".join(c.args[0] for c in mock.call_args_list)
+            values.append(flattened_bytes)
+        # Different block lengths should always feed the same number
+        # of bytes
+        assert len(set(values)) == 1
+
 
 class TestSubmissions:
     @pytest.fixture(autouse=True)

From 15f8ae24d365ad03e46bffbd4bc53e8447fb9b65 Mon Sep 17 00:00:00 2001
From: Sebastian Mohr <sebastian@mohrenclan.de>
Date: Thu, 9 Apr 2026 15:22:05 +0200
Subject: [PATCH 3/3] Apt get update should fix the broken dependency
 installation.

---
 .github/workflows/main.yml | 1 +
 test/test_acoustid.py      | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 4420f11..bd81047 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -28,6 +28,7 @@ jobs:
 
       - name: Install system dependencies
         run: |
+          sudo apt-get update
           sudo apt install --yes --no-install-recommends \
           gstreamer1.0-plugins-good \
           gstreamer1.0-plugins-bad \
diff --git a/test/test_acoustid.py b/test/test_acoustid.py
index 3cd16b4..76fab98 100644
--- a/test/test_acoustid.py
+++ b/test/test_acoustid.py
@@ -288,13 +288,14 @@ def chunk_by_size(lst, size):
                 1,
                 chunk_by_size(data, b),
                 5,
-                # Half the block is consumed -> 5*2 = 10
+                # Twice the maxlength is consumed/feed -> 5*2 = 10
             )
 
             flattened_bytes = b"".join(c.args[0] for c in mock.call_args_list)
             values.append(flattened_bytes)
-        # Different block lengths should always feed the same number
-        # of bytes
+
+        # Regardless of the block chunking
+        # we always feed the same bytes!
         assert len(set(values)) == 1