MathewSachin/Captura · error · NotSupportedException

Unknown Grabber Media Format

Error message

Unknown Grabber Media Format

What it means

Thrown by CaptureWebcam (src/Captura.Windows/Webcam/CaptureWebcam.cs:465) as NotSupportedException when the DirectShow sample grabber's connected media type is not FormatType.VideoInfo or has a zero formatPtr. The code only handles the VideoInfo header layout, so any camera that negotiates VideoInfo2 (or another format type) is rejected.

Source

Thrown at src/Captura.Windows/Webcam/CaptureWebcam.cs:465

                    Marshal.ThrowExceptionForHR(hr);

                // Make the video window visible, now that it is properly positioned
                hr = _videoWindow.put_Visible(OABool.True);

                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);

                _isPreviewRendered = true;
                didSomething = true;

                var media = new AMMediaType();
                hr = _sampGrabber.GetConnectedMediaType(media);

                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);

                if (media.formatType != FormatType.VideoInfo || media.formatPtr == IntPtr.Zero)
                    throw new NotSupportedException("Unknown Grabber Media Format");

                _videoInfoHeader = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader));

                Marshal.FreeCoTaskMem(media.formatPtr);
                media.formatPtr = IntPtr.Zero;
            }

            if (didSomething)
                _actualGraphState = GraphState.Rendered;
        }

        /// <summary>
        ///  Setup and start the preview window if the user has
        ///  requested it (by setting PreviewWindow).
        /// </summary>
        void StartPreviewIfNeeded()
        {
            // Render preview 

View on GitHub (pinned to 3fdf41529b)

Solutions

1. Add a branch that handles FormatType.VideoInfo2 by reading VideoInfoHeader2 and deriving the equivalent VideoInfoHeader.
2. Force the grabber input pin to negotiate a VideoInfo media type (set AMMediaType before connection).
3. Try a different resolution or pixel format on the camera that is offered as VideoInfo.
4. Test with another webcam to confirm it is media-type-specific.

Example fix

// before
if (media.formatType != FormatType.VideoInfo || media.formatPtr == IntPtr.Zero)
    throw new NotSupportedException("Unknown Grabber Media Format");
_videoInfoHeader = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader));
// after
if (media.formatType == FormatType.VideoInfo && media.formatPtr != IntPtr.Zero)
    _videoInfoHeader = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader));
else if (media.formatType == FormatType.VideoInfo2 && media.formatPtr != IntPtr.Zero)
    _videoInfoHeader = ((VideoInfoHeader2)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader2))).ToVideoInfoHeader();
else
    throw new NotSupportedException($"Unsupported grabber media format: {media.formatType}");

// before connecting the grabber, enumerate offered media types and prefer VideoInfo
var preferred = offered.FirstOrDefault(m => m.formatType == FormatType.VideoInfo);
if (preferred != null) pin.Connect(preferred);

static bool SupportsVideoInfo(AMMediaType m)
    => m.formatType == FormatType.VideoInfo && m.formatPtr != IntPtr.Zero;

try { /* configure grabber */ }
catch (NotSupportedException e) when (e.Message.Contains("Grabber Media Format")) { /* add VideoInfo2 handling or switch camera */ }

When it happens

Trigger: After ISampleGrabber.GetConnectedMediaType, media.formatType != FormatType.VideoInfo or media.formatPtr == IntPtr.Zero. Webcams commonly expose VideoInfo2 (carrying interlacing/anamorphic info) instead of VideoInfo, especially at certain resolutions or on newer drivers.

Common situations: A camera that only offers VideoInfo2 at the chosen resolution; a UVC driver preferring VideoInfo2; requesting a resolution/pixel format that the camera satisfies via VideoInfo2; a disconnected/zero-format pin.

Related errors

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• An Error Occurred with FFmpeg, Exit Code: {ExitCode}.\nSee F

AI-assisted analysis of MathewSachin/Captura@3fdf41529b (2026-08-13). Data as JSON: /api/errors/079d7ad683b110ce. Report an issue: GitHub.