What causes "Failed to initialize mpv: {_mpvContext.GetErrorString(err)}" in SubtitleEdit/subtitleedit?

Re-ship/restore the libmpv binary in the application directory.

SubtitleEdit/subtitleedit · error · InvalidOperationException

Failed to initialize mpv: {_mpvContext.GetErrorString(err)}

Error message

Failed to initialize mpv: {_mpvContext.GetErrorString(err)}

What it means

LibMpvDynamicPlayer.Initialize() returned a negative mpv error code; GetErrorString maps it to a human-readable string. This means the libmpv shared library could not be brought up — missing dependency, ABI mismatch, or init failure inside mpv itself. Thrown inside PlayAudio under _playLock after a fresh LibMpvDynamicPlayer is created each call.

Source

Thrown at src/ui/Features/Video/TextToSpeech/ActorVoices/ActorVoiceMappingViewModel.cs:418

        {
            row.IsPlaying = false;
            generatingAudioVm.Close();
        }
    }

    private async Task PlayAudio(string fileName)
    {
        lock (_playLock)
        {
            _mpvContext?.Stop();
            _mpvContext?.Dispose();

            _mpvContext = new LibMpvDynamicPlayer();
            _mpvContext.LoadLib();
            var err = _mpvContext.Initialize();
            if (err < 0)
            {
                throw new InvalidOperationException($"Failed to initialize mpv: {_mpvContext.GetErrorString(err)}");
            }
        }

        await _mpvContext.LoadAudio(fileName);
    }

    [RelayCommand]
    private void ApplyDefaultToAll()
    {
        if (_fallbackEngine == null)
        {
            return;
        }

        foreach (var row in Rows)
        {
            if (row.SelectedEngine == _fallbackEngine)
            {

View on GitHub (pinned to 17a9f07487)

Solutions

Re-ship/restore the libmpv binary in the application directory.
Match libmpv architecture to the process bitness (x64 process needs x64 libmpv).
Read _mpvContext.GetErrorString(err) in the message for the specific mpv error code.
Reinstall the VC++ runtime and exclude the app folder from AV.

Example fix

// before: assume init always works
var err = _mpvContext.Initialize();
// after: keep the error string in the surface message (already done) and
//       guard LoadLib separately
if (!_mpvContext.LoadLib())
    throw new InvalidOperationException("libmpv not found next to the executable");

Defensive patterns

Strategy: try-catch

Validate before calling

if (!_mpvContext.LoadLib()) return Invalid("libmpv not found next to the executable");

Try / catch

try { await PlayAudio(fileName); }
catch (InvalidOperationException ex) when (ex.Message.Contains("Failed to initialize mpv"))
{ /* surface GetErrorString; offer to re-install libmpv */ }

Prevention

Ship the matching-architecture libmpv with the app.
Call LoadLib() and check its bool before Initialize().
Log GetErrorString(err) so the mpv error code is never lost.

When it happens

Trigger: LoadLib() succeeded but Initialize() < 0: libmpv dll/so missing from the app directory; wrong architecture (x86 vs x64) vs the process; corrupt libmpv; required codec/sentenceit libs absent; AV/sandbox blocking the dll.

Common situations: App moved without its libmpv binary; user replaced libmpv with an incompatible version; fresh machine missing VC++ runtime; antivirus quarantined the dll.

Related errors

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/8e8d39ee45fb0f17. Report an issue: GitHub.