Comfy-Org/ComfyUI · error · ValueError

Unsupported audio format: {format!r}

Error message

Unsupported audio format: {format!r}

What it means

AudioSaveHelper.save_audio (comfy_api/latest/_ui.py) writes audio with soundfile/ffmpeg-backed encoders and only accepts formats in {'flac','mp3','opus'} as defined by the class-level _FORMATS set. Any other format string ('wav', 'aac', 'ogg'…) fails an explicit allowlist check before any file IO.

Source

Thrown at comfy_api/latest/_ui.py:275

        return SavedImages([result], is_animated=len(images) > 1)


class AudioSaveHelper:
    """A helper class with static methods to handle audio saving and metadata."""
    _OPUS_RATES = [8000, 12000, 16000, 24000, 48000]
    _FORMATS = {"flac", "mp3", "opus"}

    @staticmethod
    def save_audio(
        audio: dict,
        filename_prefix: str,
        folder_type: FolderType,
        cls: type[ComfyNode] | None,
        format: str = "flac",
        quality: str = "128k",
    ) -> list[SavedResult]:
        if format not in AudioSaveHelper._FORMATS:
            raise ValueError(f"Unsupported audio format: {format!r}")

        full_output_folder, filename, counter, subfolder, _ = folder_paths.get_save_image_path(
            filename_prefix, _get_directory_by_folder_type(folder_type)
        )

        metadata = {}
        if not args.disable_metadata and cls is not None:
            if cls.hidden.prompt is not None:
                metadata["prompt"] = json.dumps(cls.hidden.prompt)
            if cls.hidden.extra_pnginfo is not None:
                for x in cls.hidden.extra_pnginfo:
                    metadata[x] = json.dumps(cls.hidden.extra_pnginfo[x])

        results = []
        for batch_number, waveform in enumerate(audio["waveform"].cpu()):
            filename_with_batch_num = filename.replace("%batch_num%", str(batch_number))
            file = f"{filename_with_batch_num}_{counter:05}.{format}"
            output_path = os.path.join(full_output_folder, file)

View on GitHub (pinned to 1c6d8d45b3)

Solutions

1. Use one of the supported formats: 'flac' (lossless default), 'mp3', or 'opus'
2. If you maintain the node, keep the format widget list limited to AudioSaveHelper._FORMATS
3. Need wav? Save as flac (also lossless) or convert externally after export

Example fix

// before
save_audio(audio, prefix, folder_type, cls, format='wav')

// after
save_audio(audio, prefix, folder_type, cls, format='flac')

SUPPORTED = {'flac', 'mp3', 'opus'}
if format not in SUPPORTED:
    raise ValueError(f'format must be one of {sorted(SUPPORTED)}, got {format!r}')

def is_supported_audio_format(f) -> bool:
    return isinstance(f, str) and f in {'flac', 'mp3', 'opus'}

When it happens

Trigger: Calling save_audio with a format argument outside {'flac','mp3','opus'} — typically passed straight through from a SaveAudio-style node's format widget or an API request field.

Common situations: Custom nodes extending the format combo with wav/aac without extending _FORMATS; API clients sending arbitrary strings; frontend/backend option lists out of sync after an upgrade.

Related errors

• ERROR: audio encoder file is invalid or unsupported embed_di
• ERROR: audio encoder not supported.
• Minimum cutoff must be larger than zero.
• A cutoff above 0.5 does not make sense.
• Unknown resblock type: {self.resblock}

AI-assisted analysis of Comfy-Org/ComfyUI@1c6d8d45b3 (2026-08-14). Data as JSON: /api/errors/dd2cf41a4d691913. Report an issue: GitHub.