Can't scrub through audio/video playing in WebView from MemoryStream on UWP

Question

Hi,
I'm building a Xamarin.Forms app and want to play video and audio files from MemoryStream in a WebView (background: all content will actually be stored encrypted on the device in FileSystem.CacheDirectory).

On UWP, I'm using a UriToStreamResolver to provide a MemoryStream for the loaded resources to my WebView. This works fine except that scrubbing/skipping through audio and video does not work.

I compiled a small test project (without the decryption part) where the UriToStreamResolver looks like this:

public class UriToStreamResolver : IUriToStreamResolver 
    {
        public IAsyncOperation<IInputStream> UriToStreamAsync(Uri uri)
        {
            if (uri == null)
            {
                throw new Exception();
            }
            var path = uri.AbsolutePath;

            return GetContent(path).AsAsyncOperation();
        }

        private async Task<IInputStream> GetContent(string path)
        {
            try
            {
                var localUri = new Uri("ms-appdata://" + path); // e.g. path = "/LocalCache/video.mp4"
                var storageFile = await StorageFile.GetFileFromApplicationUriAsync(localUri);
                using var fileStream = await storageFile.OpenAsync(FileAccessMode.Read);
                // return fileStream .GetInputStreamAt(0);

                using var memoryStream = new InMemoryRandomAccessStream();
                await fileStream.AsStream().CopyToAsync(memoryStream.AsStream());

                return memoryStream.GetInputStreamAt(0);
            }
            catch (Exception e)
            {
                Debug.WriteLine("Invalid path:" + e.Message);
                throw new Exception("Invalid path");
            }
        }
    }

Even returning the file's IRandomAccessStream directly (line 21) prevents scrub/skip ability.

Is this a bug or just the wrong approach?
(I noticed that, when navigating to a video/audio file directly, the method will be called twice for some reason which is, of course, suboptimal when loading the file to memory. When embedding media files with audio/video tag in html, it will only be called once, as expected. The scrubbing problem persists even in this case, however.)

Thanks for your support!
Simon

Answer 1

Hello @scb Welcome to Microsoft Q&A

Can't scrub through audio/video playing in WebView from MemoryStream on UWP

I could reproduce your problem, the src uri cause the problem, In UWP platform, we suggest you use ms-appx:/// uri scheme. During my testing, the progress bar could be seek with the following src.

<video src="ms-appx:///Assets/files/video.mp4" controls></video>  

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