deezer/spleeter · error · SpleeterError

FFMPEG error: {process.stderr.read()}

Error message

FFMPEG error: {process.stderr.read()}

What it means

When saving, spleeter pipes raw float32 PCM bytes into a running ffmpeg process's stdin. If writing to stdin, closing it, or waiting on the process raises IOError (typically because ffmpeg died and closed the pipe), spleeter wraps it in a `SpleeterError` containing ffmpeg's stderr output.

Source

Thrown at spleeter/audio/ffmpeg.py:184

        logger.debug(f"Writing file {path}")
        input_kwargs = {"ar": sample_rate, "ac": data.shape[1]}
        output_kwargs = {"ar": sample_rate, "strict": "-2"}
        if bitrate:
            output_kwargs["audio_bitrate"] = bitrate
        if codec is not None and codec != "wav":
            output_kwargs["codec"] = self.SUPPORTED_CODECS.get(codec, codec)
        process = (
            ffmpeg.input("pipe:", format="f32le", **input_kwargs)
            .output(path, **output_kwargs)
            .overwrite_output()
            .run_async(pipe_stdin=True, pipe_stderr=True, quiet=True)
        )
        try:
            process.stdin.write(data.astype("<f4").tobytes())
            process.stdin.close()
            process.wait()
        except IOError:
            raise SpleeterError(f"FFMPEG error: {process.stderr.read()}")
        logger.info(f"File {path} written succesfully")

View on GitHub (pinned to c8854001ac)

Solutions

1. Read the embedded ffmpeg stderr in the error message for the concrete ffmpeg failure
2. Try a safe default first: `codec='wav'` with no bitrate to isolate the issue
3. Validate the codec/bitrate/filename-extension combination is supported by your ffmpeg build (`ffmpeg -codecs`)

Example fix

// before
adapter.save('out.ogg', data, 44100, codec='opus', bitrate='999k')
// after
adapter.save('out.wav', data, 44100, codec='wav')  # confirm pipeline works, then retry desired codec

# sanity-check inputs before saving
import shutil
assert shutil.which('ffmpeg') is not None
assert data.ndim == 2, 'data must be (samples, channels)'
extension = path.rsplit('.', 1)[-1].lower()
assert extension in ('wav', 'mp3', 'ogg', 'flac', 'm4a'), f'unsupported extension: {extension}'

try:
    adapter.save(path, data, sample_rate, codec='wav')
except Exception as e:
    if 'FFMPEG error' in str(e):
        logger.error('ffmpeg failed writing %s: %s', path, str(e))
        adapter.save(path.with_suffix('.wav'), data, sample_rate, codec='wav')
    else:
        raise

When it happens

Trigger: Calling `adapter.save(path, data, sample_rate, ...)` where the spawned ffmpeg process exits early or fails: bad codec/bitrate combination, unsupported output extension, ffmpeg crashing on the data shape/channels.

Common situations: Requesting an exotic codec or bitrate (e.g. with `codec='aac'` and an unsupported bitrate), writing to a filename with an extension ffmpeg cannot infer a format from, out-of-memory kill of the ffmpeg process, or incompatible `strict -2` format options.

Related errors

• An error occurs with ffprobe (see ffprobe output below) {}
• {} binary not found
• No stream was found with ffprobe
• output directory does not exists: {directory}

AI-assisted analysis of deezer/spleeter@c8854001ac (2026-08-28). Data as JSON: /api/errors/b257724693339fdb. Report an issue: GitHub.