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This PR resolves a critical runtime crash during the audio export stage on Linux systems, specifically occurring in Cloud environments like Lightning AI. #1089

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This PR resolves a critical runtime crash during the audio export stage on Linux systems, specifically occurring in Cloud environments like Lightning AI. #1089

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ed95f0e
fix(audio): resolve export crashes on Linux/Cloud envs like lightning…
Apr 11, 2026
0457406
Fix audio export handling and improve cloud GPU compatibility
Apr 13, 2026
7f4b5db
Merge branch 'main' into fix/audio-export-linux
sobiswriter Apr 13, 2026
025006e
Merge branch 'ace-step:main' into fix/audio-export-linux
sobiswriter Apr 15, 2026
16be021
feat: fixed the default .env.example & the install.md documentation f…
Apr 15, 2026
6dba85e
Update INSTALL.md for clarity and formatting
sobiswriter Apr 15, 2026
da822f3
Clean up blank lines in .env.example
sobiswriter Apr 15, 2026
b5601df
Merge branch 'main' into fix/audio-export-linux
sobiswriter Apr 25, 2026
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6 changes: 5 additions & 1 deletion .env.example
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,10 @@ ACESTEP_LM_BACKEND=vllm
#
# Default: auto (based on GPU VRAM detection)
ACESTEP_INIT_LLM=auto
# Force all audio exports to FLAC as a workaround for torchcodec/FFmpeg
# load failures on some cloud GPU environments (Lightning AI, Lambda, etc.)
# Leave unset or =0 to respect the format chosen in the UI
# ACESTEP_FORCE_FLAC_EXPORT=0

# ==================== Model Storage ====================
# Shared checkpoints directory (useful when running multiple installations)
Expand Down Expand Up @@ -81,4 +85,4 @@ ACESTEP_INIT_LLM=auto
# ==================== Startup Settings ====================
# By default models are lazy-loaded on first request (fast server startup).
# Set to false to force eager model loading at startup.
# ACESTEP_NO_INIT=true
# ACESTEP_NO_INIT=true
8 changes: 7 additions & 1 deletion acestep/audio_utils.py
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Expand Up @@ -215,6 +215,10 @@ def save_audio(
Actual saved file path
"""
format = (format or self.default_format).lower()

force_flac = os.getenv("ACESTEP_FORCE_FLAC_EXPORT", "0") == "1"
if force_flac:
format = "flac"
Comment on lines +219 to +221
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@coderabbitai coderabbitai Bot Apr 13, 2026

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⚠️ Potential issue | 🔴 Critical

Forced FLAC can produce extension/content mismatch (e.g., .mp3 file containing FLAC).

At Line 221, format is forced to "flac", but if output_path already has .mp3/.wav (Line 233), suffix normalization won’t rewrite it. With upstream callers prebuilding names from requested format, this can save FLAC bytes under non-FLAC extensions.

Proposed fix 
         force_flac = os.getenv("ACESTEP_FORCE_FLAC_EXPORT", "0") == "1"
         if force_flac:
-            format = "flac" 
+            format = "flac"

         # Ensure output path has correct extension
         output_path = Path(output_path)
+        if force_flac and output_path.suffix.lower() != ".flac":
+            output_path = output_path.with_suffix(".flac")

Also applies to: 228-240

🧰 Tools
🪛 Ruff (0.15.9)

[error] 222-222: Variable format is shadowing a Python builtin

(A001)

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@acestep/audio_utils.py` around lines 220 - 222, The current force_flac branch
sets format = "flac" but leaves output_path's filename/extension unchanged,
causing extension/content mismatches; when ACESTEP_FORCE_FLAC_EXPORT is "1"
(force_flac), update output_path to match the forced format (e.g., use
pathlib.Path(output_path).with_suffix(f".{format}") or rebuild the filename from
format) and ensure any downstream suffix normalization logic (the block around
output_path and its suffix handling) uses the updated format so saved bytes and
file extension are consistent; reference the force_flac variable, format
assignment, and output_path handling in your change.

if format not in ["flac", "wav", "mp3", "wav32", "opus", "aac"]:
logger.warning(f"Unsupported format {format}, using {self.default_format}")
format = self.default_format
Expand Down Expand Up @@ -308,8 +312,10 @@ def save_audio(
str(output_path),
audio_tensor,
sample_rate,
channels_first=True,
channels_first=channels_first,
#backend="soundfile" #safe dependency
)


logger.debug(f"[AudioSaver] Saved audio to {output_path} ({format}, {sample_rate}Hz)")
return str(output_path)
Expand Down
14 changes: 13 additions & 1 deletion docs/en/INSTALL.md
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Expand Up @@ -127,7 +127,19 @@ chmod +x start_gradio_ui.sh start_api_server.sh
# Launch REST API Server
./start_api_server.sh
```

> [!IMPORTANT]
> **Cloud GPU Users (Lightning AI, Lambda, etc.):**
> To prevent audio export crashes (`libtorchcodec` or `libavutil` errors), install the required system packages **before** running the app:
>
> ```bash
> sudo apt-get update && sudo apt-get install -y ffmpeg libavdevice60 libavcodec-extra
> ```
>
> If you still see torchcodec / FFmpeg load errors, export `LD_LIBRARY_PATH` in the same shell that launches the app:
>
> ```bash
> export LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:$LD_LIBRARY_PATH
> ```
> **Note:** Git must be installed via your system package manager (`sudo apt install git`, `sudo yum install git`, `sudo pacman -S git`).

### macOS (Apple Silicon / MLX)
Expand Down