SubtitleEdit/subtitleedit · error · InvalidOperationException

Failed to create software render context: {GetErrorString(er

Error message

Failed to create software render context: {GetErrorString(err)}

What it means

InvalidOperationException: mpv_render_context_create returned a negative code for the MPV_RENDER_API_TYPE_SW parameters. The mpv core initialized successfully but could not create a software render context.

Source

Thrown at src/ui/Logic/VideoPlayers/LibMpvDynamic/LibMpvDynamicPlayer.cs:1821

                new MpvRenderParam { type = MPV_RENDER_PARAM_INVALID, data = IntPtr.Zero }
            };

            var renderParamsSize = Marshal.SizeOf<MpvRenderParam>() * renderParams.Length;
            var renderParamsPtr = Marshal.AllocHGlobal(renderParamsSize);

            try
            {
                for (var i = 0; i < renderParams.Length; i++)
                {
                    var offset = renderParamsPtr + (i * Marshal.SizeOf<MpvRenderParam>());
                    Marshal.StructureToPtr(renderParams[i], offset, false);
                }

                // Create render context
                err = _mpvRenderContextCreate(out _renderContext, _mpv, renderParamsPtr);
                if (err < 0)
                {
                    throw new InvalidOperationException($"Failed to create software render context: {GetErrorString(err)}");
                }

                // Set update callback
                _renderUpdateCallback = OnRenderUpdate;
                var callbackPtr = Marshal.GetFunctionPointerForDelegate(_renderUpdateCallback);
                _mpvRenderContextSetUpdateCallback(_renderContext, callbackPtr, IntPtr.Zero);
            }
            finally
            {
                Marshal.FreeHGlobal(renderParamsPtr);
            }
        }
        finally
        {
            Marshal.FreeHGlobal(apiTypePtr);
        }
    }

View on GitHub (pinned to 17a9f07487)

Solutions

1. Use a libmpv build that supports software rendering.
2. Fall back to a GPU vo render context when software context creation fails.
3. Verify the MpvRenderParam marshalling matches the linked libmpv's ABI.

Example fix

// before
err = _mpvRenderContextCreate(out _renderContext, _mpv, renderParamsPtr);
if (err < 0) throw new InvalidOperationException($"Failed to create software render context: {GetErrorString(err)}");

// after
err = _mpvRenderContextCreate(out _renderContext, _mpv, renderParamsPtr);
if (err < 0)
{
    logger.LogWarning("software render context unavailable: {Msg}", GetErrorString(err));
    await SwitchToGpuVoAsync();
}

if (!LibMpvSupportsSoftwareRender())
{
    logger.LogWarning("libmpv has no SW render; using GPU vo");
    SwitchToGpuVo();
    return;
}

try { player.InitializeWithSoftwareRendering(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("software render context"))
{
    logger.LogWarning("{Msg}; falling back to GPU vo", ex.Message);
    await SwitchToGpuVoAsync();
}

When it happens

Trigger: A libmpv build compiled without software-render support, an SW render API type unsupported by the loaded build, a GPU-only libmpv, or an MpvRenderParam struct layout mismatch across ABI versions.

Common situations: Minimal or embedded libmpv builds, or a version skew where the marshalled MpvRenderParam layout no longer matches the linked library.

Related errors

• MPV delegates not loaded for software rendering.
• Failed to initialize mpv: {_mpvContext.GetErrorString(err)}
• Failed to initialize mpv: {_mpvContext.GetErrorString(err)}
• Failed to initialize mpv: {player.GetErrorString(err)}
• Failed to initialize mpv: {_mpvPlayer.GetErrorString(err)}

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/2f7fea35f96330fb. Report an issue: GitHub.