Fix G.722 ADPCM state reset causing robotic/truncated echo audio by Copilot · Pull Request #43 · codingjoe/VoIP

Copilot · 2026-03-16T10:32:55Z

G722.decode created a new av.open() context per RTP packet, resetting the ADPCM predictor to zero every 20 ms. Since the remote encoder accumulates predictor state across packets, only packet 0 decoded correctly — packets 1+ decoded to near-silence. The VAD discarded these silent frames, so the speech buffer collected ≈20 ms of audio regardless of utterance length, producing a truncated, robotic echo.

Changes

voip/codecs/g722.py — G722Decoder: stateful decoder dataclass that holds a single persistent av.CodecContext(sample_rate=16000) for the call lifetime; each packet is fed into the same context, preserving predictor state across boundaries.
voip/codecs/g722.py — G722.create_decoder: factory classmethod returning a G722Decoder for per-call use.
voip/codecs/base.py — decoder infrastructure:
- PayloadDecoder Protocol — common interface (decode(bytes) → np.ndarray)
- PerPacketDecoder — stateless wrapper for PCMA/PCMU/Opus; delegates to RTPCodec.decode per packet (preserves existing behavior)
- RTPCodec.create_decoder() — default factory, returns PerPacketDecoder; overridden by G722
voip/audio.py — AudioCall: __post_init__ now calls codec.create_decoder() and stores the result as payload_decoder; decode_payload delegates to self.payload_decoder.decode(payload).

# G.722 call → stateful G722Decoder (preserves ADPCM state)
call = AudioCall(rtp=..., sip=..., media=g722_media, caller=...)
assert isinstance(call.payload_decoder, G722Decoder)

# PCMA/PCMU/Opus → PerPacketDecoder (stateless, unchanged behaviour)
call = AudioCall(rtp=..., sip=..., media=pcma_media, caller=...)
assert isinstance(call.payload_decoder, PerPacketDecoder)

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

releases.astral.sh
- Triggering command: /home/REDACTED/.local/bin/uv /home/REDACTED/.local/bin/uv run --extra=audio --extra=hd-audio pytest tests/codecs/test_g722.py tests/test_audio.py -x -q (dns block)
stun.cloudflare.com
- Triggering command: /home/REDACTED/work/VoIP/VoIP/.venv/bin/pytest pytest -q (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

This section details on the original issue you should resolve

<issue_title>🐛 G.722 is sounding off</issue_title>
<issue_description>### Bug Description

When I use the echo call, the response is audible but broken. It seems too short and sounds "like a robot". The pitch and gain seem correct.

Expected Behavior

I should hear my voice in the echo call clear as day, since it's a high-res call and I have a wired broadband connection to the UAS. My ping stats are round-trip min/avg/max/stddev = 26.084/29.938/32.507/2.109 ms.

Version

0.2.1

Stack trace

No response

Steps to Reproduce

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

Custom agent used: SuperJoe
CodingJoe's digital clone following his coding guidelines and best practices.

Fixes 🐛 G.722 is sounding off #42

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codecov · 2026-03-16T10:33:53Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.25%. Comparing base (aaed58f) to head (446800f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #43      +/-   ##
==========================================
+ Coverage   94.13%   94.25%   +0.11%     
==========================================
  Files          24       24              
  Lines        1723     1759      +36     
==========================================
+ Hits         1622     1658      +36     
  Misses        101      101

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

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codingjoe

GTM

Copilot

Pull request overview

Adds per-call, stateful G.722 decoding to preserve ADPCM predictor state across RTP packets, fixing truncated/robotic audio in echo/VAD flows.

Changes:

Introduce PayloadDecoder + RTPCodec.create_decoder() and a PerPacketDecoder default to support per-call decoder instances.
Add G722Decoder dataclass holding a persistent PyAV codec context, and override G722.create_decoder() to return it.
Update AudioCall to instantiate and use a per-call payload_decoder; extend tests and docs accordingly.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`voip/codecs/g722.py`	Adds `G722Decoder` and `G722.create_decoder()` for stateful per-call decode.
`voip/codecs/base.py`	Adds decoder protocol + default per-packet decoder factory infrastructure.
`voip/audio.py`	Switches payload decoding to a per-call decoder instance (`payload_decoder`).
`tests/test_audio.py`	Updates/extends `AudioCall.decode_payload` tests for decoder routing.
`tests/codecs/test_g722.py`	Adds tests validating stateful decoding and documenting the original bug.
`tests/codecs/test_base.py`	Adds tests for `RTPCodec.create_decoder()` / `PerPacketDecoder`.
`docs/codecs.md`	Documents new decoder types in API docs.

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voip/codecs/base.py

voip/codecs/g722.py

docs/codecs.md

Co-authored-by: Copilot Autofix powered by AI <[email protected]>

codingjoe · 2026-03-16T13:43:46Z

@copilot this worked for the echo call, but the agent suffers from the same strange sound. Open a new PR against main and check if the TTS output is correctly send via G.722

Initial plan

78afd0c

Copilot AI assigned Copilot and codingjoe Mar 16, 2026

Copilot started work on behalf of codingjoe March 16, 2026 10:33 View session

Copilot AI and others added 2 commits March 16, 2026 11:01

Fix G.722 ADPCM state reset causing robotic echo audio

ba551a4

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

Address code review: improve docstring types, rename test helpers

72ab79b

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

Copilot AI changed the title ~~[WIP] [G-722] Fix broken audio in echo call~~ Fix G.722 ADPCM state reset causing robotic/truncated echo audio Mar 16, 2026

Copilot AI requested a review from codingjoe March 16, 2026 11:04

Copilot finished work on behalf of codingjoe March 16, 2026 11:04

codingjoe and others added 2 commits March 16, 2026 12:34

Fix docs

d1af167

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

05f07a9

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

codingjoe approved these changes Mar 16, 2026

View reviewed changes

codingjoe marked this pull request as ready for review March 16, 2026 11:45

Copilot AI review requested due to automatic review settings March 16, 2026 11:45

Copilot started reviewing on behalf of codingjoe March 16, 2026 11:46 View session

Copilot AI reviewed Mar 16, 2026

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Co-authored-by: Copilot Autofix powered by AI <[email protected]>

codingjoe merged commit 4dc14e2 into main Mar 16, 2026
24 checks passed

codingjoe deleted the copilot/fix-g722-sound-issue branch March 16, 2026 12:37

codingjoe mentioned this pull request Mar 16, 2026

🐛 G.722 is sounding off #42

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Copilot AI mentioned this pull request Mar 16, 2026

Fix G.722 ADPCM state reset between TTS chunks causing robotic audio #47

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Fix G.722 ADPCM state reset causing robotic/truncated echo audio#43

Fix G.722 ADPCM state reset causing robotic/truncated echo audio#43
codingjoe merged 6 commits intomainfrom
copilot/fix-g722-sound-issue

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I tried to connect to the following addresses, but was blocked by firewall rules:

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