Bug: Opus output truncates last ~1.5s of audio due to OGG container not being closed before buffer read

[dprev]

Bug Description

When requesting audio in opus format, the output is truncated by approximately 1.5–2 seconds at the end. The same text rendered as mp3 produces the correct full-length audio.

Reproduction

Send identical text to the TTS endpoint requesting both opus and mp3 output formats and compare durations:

# Opus output
curl -s -X POST http://localhost:8880/v1/audio/speech \
  -H 'Content-Type: application/json' \
  -d '{"model":"kokoro","input":"One two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen twenty.","voice":"af_heart","response_format":"opus"}' \
  --output test.opus

# MP3 output  
curl -s -X POST http://localhost:8880/v1/audio/speech \
  -H 'Content-Type: application/json' \
  -d '{"model":"kokoro","input":"One two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen twenty.","voice":"af_heart","response_format":"mp3"}' \
  --output test.mp3

ffprobe -v quiet -show_entries format=duration -of csv=p=0 test.opus  # → 8.0s
ffprobe -v quiet -show_entries format=duration -of csv=p=0 test.mp3   # → 9.6s

Root Cause

In api/src/services/streaming_audio_writer.py, the write_chunk(finalize=True) path reads the output buffer before closing the OGG container:

# Current (buggy) order:
packets = self.stream.encode(None)
for packet in packets:
    self.container.mux(packet)

data = self.output_buffer.getvalue()  # ← reads buffer HERE
self.close()                           # ← container.close() writes final OGG pages AFTER
return data                            # ← missing the OGG trailer

For opus (OGG container), container.close() writes the final OGG pages (container trailer/footer). Since getvalue() is called first, those final pages are silently lost. MP3 is frame-based with no container trailer, so it is unaffected.

Fix

Close the container before reading the buffer:

# Fixed order:
self.container.close()
data = self.output_buffer.getvalue()
self.output_buffer.close()
return data

Environment

• Image: ghcr.io/remsky/kokoro-fastapi-cpu:latest
• Version: v0.2.4-master (pulled 2026-02-15)

[ppetermann]

this is the same as #447 isn't it? there is a pr for it #448 - which is the same fix you are proposing

[dprev]

Thanks for flagging — you're right, it's the same bug. I filed this independently on Feb 17 after hitting it on the CPU Docker build and didn't spot #447 when searching (the titles diverged enough to miss each other).

Good to see #448 already has the fix in flight — the root cause analysis matches exactly. Happy to close this as a duplicate once #448 lands. Cheers.