stride3d/stride · error · ApplicationException

Could not open file.

Error message

Could not open file.

What it means

FFmpegMedia.Open throws this ApplicationException when ffmpeg.avformat_open_input returns a negative code, meaning FFmpeg could not open the input at the given URL. The hex code and av_strerror text are logged, then a generic 'Could not open file.' exception is thrown.

Solutions

1. Check the logged hex code / av_strerror output to distinguish file-not-found, permission, and protocol errors.
2. Verify the file exists and the path is absolute/resolved correctly at runtime.
3. Validate that startPosition/length fall within the file (they build a subfile,,start,X,end,Y,,:url URL).
4. Deploy the file with the application (mark as content) and check read permissions.

Example fix

// before
media.Open("video.mp4", startPosition: 0, length: -1); // file not deployed
// after
var path = Path.Combine(AppContext.BaseDirectory, "Content", "video.mp4");
if (!File.Exists(path)) throw new FileNotFoundException(path);
media.Open(path, startPosition: 0, length: -1);

if (!File.Exists(path))
    throw new FileNotFoundException($"Media file missing: {path}");

try
{
    media.Open(url, startPosition, length);
}
catch (ApplicationException ex) when (ex.Message == "Could not open file.")
{
    // check logs for the hex code; verify path/permissions and retry or surface to user
}

When it happens

Trigger: Calling Open (or CreateAssets/DoCommandOverride) with a url that does not exist, is malformed, is inaccessible, or whose subfile,start/end range is invalid; also when the file is disposed mid-call (ObjectDisposedException is checked before, but the FFmpeg open can still fail).

Common situations: Wrong or relative path for the media file; file missing at runtime after build/deployment (content not copied); invalid startPosition/length combination producing a bad subfile protocol URL; unsupported protocol or permission issues; corrupt container FFmpeg cannot probe.

Understand the failure class

Background: "open() failed", "failed to open file", "cannot create file" — what a file open error means and how to fix it — this error's family across 42 libraries.

Related errors

• Could not find stream info.
• Could not fill codec parameters. Error code=
• Could not find function
• Could not initialize the conversion context.
• Could not open codec. Error code=

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/74c66dfc141a10d3. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.Video/FFmpeg/FFmpegMedia.cs:137

        public void Open(string url, long startPosition = 0, long length = -1)
        {
            FFmpegUtils.EnsurePlatformSupport();
            if (isDisposed)
                throw new ObjectDisposedException(nameof(FFmpegMedia));
            if (IsOpen)
                // TODO: log?
                throw new InvalidOperationException(@"Media is already open.");

            if (startPosition != 0 && length != -1)
                url = $@"subfile,,start,{startPosition},end,{startPosition + length},,:{url}";

            var pFormatContext = ffmpeg.avformat_alloc_context();
            var ret = ffmpeg.avformat_open_input(&pFormatContext, url, null, null);
            if (ret < 0)
            {
                Logger.Error($"Could not open file. Error code={ret.ToString("X8")}");
                Logger.Error(GetErrorMessage(ret));
                throw new ApplicationException(@"Could not open file.");
            }

            ret = ffmpeg.avformat_find_stream_info(pFormatContext, null);
            if (ret < 0)
            {
                Logger.Error($"Could not find stream info. Error code={ret.ToString("X8")}");
                Logger.Error(GetErrorMessage(ret));
                throw new ApplicationException(@"Could not find stream info.");
            }

            AVFormatContext = pFormatContext;
            Duration = TimeSpan.FromSeconds((double)AVFormatContext->duration / ffmpeg.AV_TIME_BASE);
            Url = url;

            // Get the streams
            for (int i = 0; i < pFormatContext->nb_streams; i++)
            {
                var stream = FFmpegStream.Create(pFormatContext->streams[i], this);

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