Fix G.711 codec algorithms, resample edge cases, and conditional `__all__` by Copilot · Pull Request #41 · codingjoe/VoIP

Copilot · 2026-03-15T22:21:47Z

Addresses several correctness issues in the G.711 codec layer introduced during the codec base-class refactor: wrong µ-law/A-law decode formulas, input_rate_hz ignored as source rate, __all__ exporting undefined names without PyAV, and resample() crashing on edge inputs.

PCMU (µ-law)

Decode formula: Replaced (mantissa | 0x10) << (exp + 3) with the canonical ITU-T G.711 expansion:

magnitude = (((mantissa << 3) + _MU_LAW_BIAS) << exp) - _MU_LAW_BIAS

Silence codeword 0x7F now decodes to exactly 0.0 instead of a small non-zero value.

PCMA (A-law)

Segmented algorithm: Replaced the continuous companding approximation (log/exp) with the standard ITU-T G.711 segmented codec (Sun g711.c, 16-bit scale). Codeword 0xAA now decodes to exactly 0.984375 per spec, enabling bit-exact interop with real RTP streams.

Vectorized segment lookup: Segment index determination uses np.searchsorted instead of an 8-step Python loop.

Both PCMA and PCMU

input_rate_hz as source rate: decode() now uses input_rate_hz (when provided) as the resampling source rate, correctly handling non-standard G.711 clock rates advertised in SDP (e.g. PCMA/16000).

`voip/codecs/init.py`

Conditional __all__: G722, Opus, PyAVCodec are now appended to __all__ only when the try import succeeds, preventing from voip.codecs import * from raising AttributeError in environments without PyAV.

`RTPCodec.resample()`

Edge cases: Returns an empty float32 array for empty input; clamps n_out to a minimum of 1 for non-empty input, avoiding numpy.interp failures during aggressive downsampling.

Tests

Golden codeword assertions: PCMU 0x7F → 0.0, PCMA 0xAA → 0.984375, PCMA 1.0 → 0xAA, PCMA 0.0 → 0xD5
input_rate_hz-as-source-rate tests for both codecs
resample() empty-input and single-sample heavy-downsample edge cases
__all__ conditional test (no-PyAV scenario)

📱 Kick off Copilot coding agent tasks wherever you are with GitHub Mobile, available on iOS and Android.

Co-authored-by: codingjoe <[email protected]>

codecov · 2026-03-15T22:39:55Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.13%. Comparing base (c45ca70) to head (8bc0049).
⚠️ Report is 1 commits behind head on codev.

Additional details and impacted files

@@            Coverage Diff             @@
##            codev      #41      +/-   ##
==========================================
+ Coverage   94.10%   94.13%   +0.03%     
==========================================
  Files          24       24              
  Lines        1713     1723      +10     
==========================================
+ Hits         1612     1622      +10     
  Misses        101      101

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

codingjoe

@copilot the audio quality got worse. It was perfectly fine before. Now the audio has a hissing to it.

codingjoe · 2026-03-15T22:45:54Z

voip/codecs/pcma.py

-    Both encode and decode are pure-NumPy and require no PyAV dependency.
+    Both encode and decode implement the standard G.711 segmented algorithm
+    (ITU-T G.711 Annex A) and interoperate bit-exactly with real RTP PCMA
+    streams.  No PyAV dependency is required.


Pretty verbose, keep docstrings short and to an outside perspective. We don't care about internal implementation in docstrings.

Suggested change

streams. No PyAV dependency is required.

streams.

Done in f8fb750 — shortened to "Both encode and decode interoperate bit-exactly with real RTP PCMA streams."

…tring Co-authored-by: codingjoe <[email protected]>

Copilot · 2026-03-15T22:56:10Z

@copilot the audio quality got worse. It was perfectly fine before. Now the audio has a hissing to it.

Fixed in f8fb750. The hissing was caused by a wrong mantissa shift in PCMA.encode(). G.711 A-law quantises 13-bit PCM (16-bit right-shifted by 3), so the correct shift in 16-bit space is 4 for segments 0–1 and seg + 3 for segments ≥ 2. The previous code used max(seg, 1) which is the 13-bit shift applied to 16-bit values — causing ~3× the normal quantisation error in mid-range segments (visible as hissing). A regression test for this range has been added.

codingjoe

LGTM

for more information, see https://pre-commit.ci

Copilot

Pull request overview

This PR fixes correctness issues in the pure-NumPy G.711 codecs (PCMU/PCMA), hardens RTPCodec.resample() against edge inputs, and makes voip.codecs.__all__ conditional on PyAV availability to avoid exporting undefined names.

Changes:

Correct G.711 µ-law/A-law decode/encode behavior (including honoring input_rate_hz as the resampling source rate).
Make RTPCodec.resample() handle empty input and extreme downsampling safely.
Fix voip.codecs.__all__ so PyAV-backed names are exported only when import succeeds; add/adjust tests accordingly.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`voip/codecs/pcmu.py`	Updates µ-law decode magnitude formula and uses `input_rate_hz` as resample source.
`voip/codecs/pcma.py`	Replaces A-law companding approximation with segmented G.711 algorithm; adds vectorized segment selection.
`voip/codecs/base.py`	Makes `resample()` return empty output for empty input and clamps output length to ≥ 1 for non-empty input.
`voip/codecs/__init__.py`	Makes `__all__` include PyAV-backed classes only when imports succeed.
`tests/codecs/test_pcm.py`	Adds golden codeword tests and verifies `input_rate_hz` affects resampling.
`tests/codecs/test_codecs.py`	Adds `__all__`/registry tests for “no PyAV” scenario and refactors module-key removal.
`tests/codecs/test_base.py`	Adds `resample()` edge-case tests (empty input, heavy downsample).
`pyproject.toml`	Adds `av` to the `ai` optional dependency group.

Comments suppressed due to low confidence (1)

tests/codecs/test_codecs.py:101

test_all__excludes_pyav_names_when_av_unavailable mutates sys.modules (including removing voip.codecs and setting sys.modules["av"]=None) but does not reload/restore the original voip.codecs module at the end. This can leave the voip package’s codecs attribute pointing at the temporary fresh module (or leave the av=None sentinel behind if av wasn’t previously imported), which can cause cross-test contamination. Mirror the cleanup used in test_registry__excludes_pyav_codecs_when_av_unavailable (restore av properly and reload the original module).

    def test_all__excludes_pyav_names_when_av_unavailable(self):
        """__all__ excludes G722, Opus, and PyAVCodec when av is not importable."""
        keys_to_remove = [k for k in sys.modules if k in _PYAV_MODULE_KEYS]
        saved = {k: sys.modules.pop(k) for k in keys_to_remove}
        sys.modules["av"] = None  # causes ImportError on `import av`

        try:
            import voip.codecs as fresh  # noqa: PLC0415

            for name in ("G722", "Opus", "PyAVCodec"):
                assert name not in fresh.__all__, (
                    f"{name!r} must not be in __all__ without av"
                )
        finally:
            for k in list(sys.modules):
                if k in _PYAV_MODULE_KEYS:
                    sys.modules.pop(k, None)
            sys.modules.update(saved)

You can also share your feedback on Copilot code review. Take the survey.

tests/codecs/test_codecs.py

+        keys_to_remove = [k for k in sys.modules if k in _PYAV_MODULE_KEYS]
        saved = {k: sys.modules.pop(k) for k in keys_to_remove}
        sys.modules["av"] = None  # causes ImportError on `import av`



voip/codecs/pcmu.py

-        linear = ((biased - _MU_LAW_BIAS) / 32768.0).astype(np.float32)
+        # ITU-T G.711 §A: magnitude = (((mantissa << 3) + BIAS) << exp) - BIAS
+        magnitude = (((mantissa << 3) + _MU_LAW_BIAS) << exp) - _MU_LAW_BIAS
+        linear = (magnitude.astype(np.float32) / 32768.0).astype(np.float32)


Initial plan

4e22078

Copilot AI assigned Copilot and codingjoe Mar 15, 2026

Copilot AI mentioned this pull request Mar 15, 2026

Deduplicate codec base classes #40

Merged

Copilot started work on behalf of codingjoe March 15, 2026 22:21 View session

Copilot AI and others added 2 commits March 15, 2026 22:33

Fix G.711 codec algorithms, resample edge cases, and conditional __all__

d8960ba

Co-authored-by: codingjoe <[email protected]>

Vectorize PCMA segment lookup and deduplicate test module key set

000ac53

Co-authored-by: codingjoe <[email protected]>

Copilot AI changed the title ~~[WIP] Refactor codec layer to replace Codec Protocol with RTPCodec~~ Fix G.711 codec algorithms, resample edge cases, and conditional __all__ Mar 15, 2026

Copilot AI requested a review from codingjoe March 15, 2026 22:38

Copilot finished work on behalf of codingjoe March 15, 2026 22:38

codingjoe reviewed Mar 15, 2026

View reviewed changes

Copilot started work on behalf of codingjoe March 15, 2026 22:46 View session

Fix PCMA A-law encode mantissa shift (audio hissing) and shorten docs…

f8fb750

…tring Co-authored-by: codingjoe <[email protected]>

Copilot AI requested a review from codingjoe March 15, 2026 22:56

Copilot finished work on behalf of codingjoe March 15, 2026 22:56

codingjoe approved these changes Mar 15, 2026

View reviewed changes

codingjoe and others added 2 commits March 16, 2026 00:36

Bring av back to ai

c52607a

[pre-commit.ci] auto fixes from pre-commit.com hooks

8bc0049

for more information, see https://pre-commit.ci

codingjoe marked this pull request as ready for review March 15, 2026 23:36

Copilot AI review requested due to automatic review settings March 15, 2026 23:36

codingjoe merged commit 49a7158 into codev Mar 15, 2026
19 of 20 checks passed

codingjoe deleted the copilot/sub-pr-40 branch March 15, 2026 23:36

Copilot started reviewing on behalf of codingjoe March 15, 2026 23:37 View session

Copilot AI reviewed Mar 15, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Fix G.711 codec algorithms, resample edge cases, and conditional `all`#41

Fix G.711 codec algorithms, resample edge cases, and conditional `all`#41
codingjoe merged 6 commits intocodevfrom
copilot/sub-pr-40

Copilot AI commented Mar 15, 2026 •

edited

Loading

Uh oh!

codecov bot commented Mar 15, 2026 •

edited

Loading

Uh oh!

codingjoe left a comment

Uh oh!

codingjoe Mar 15, 2026

Uh oh!

Copilot AI Mar 15, 2026

Uh oh!

Copilot AI commented Mar 15, 2026

Uh oh!

codingjoe left a comment

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Conversation

Copilot AI commented Mar 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

PCMU (µ-law)

PCMA (A-law)

Both PCMA and PCMU

voip/codecs/__init__.py

RTPCodec.resample()

Tests

Uh oh!

codecov bot commented Mar 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

codingjoe left a comment

Choose a reason for hiding this comment

Uh oh!

codingjoe Mar 15, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Mar 15, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI commented Mar 15, 2026

Uh oh!

codingjoe left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Copilot AI commented Mar 15, 2026 •

edited

Loading

`voip/codecs/init.py`

`RTPCodec.resample()`

codecov bot commented Mar 15, 2026 •

edited

Loading