MediaFailed: Cannot marshal 'parameter'

[Gikerl]

Issue Title (MediaFailed: Cannot marshal 'parameter')

Full exception message: MediaFailed: Cannot marshal 'parameter #3': Invalid managed/unmanaged type combination (String parameters and return types must be paired with LPStr, LPWStr, LPTStr, BStr, TBStr, VBByRefStr, or AnsiBStr).

This exception occurs after setting the Media.Source only on Windows 7. On Windows 10 the same URI plays just fine.

Issue Categories

• [ ] Bug

Version Information

• [ ] NuGet Package FFME.Windows 4.2.320
• [ ] NuGet Package FFME.AutoGen 4.2.0

Steps to Reproduce

1. Create a WPF Application with the FFME Mediaelement
2. During Execution change the Media Source
3. Listen to MediaFailed event and receive the exception (on Windows 7)

Expected Results

• No exception thrown like on Windows 10 machines

Sample Code

XAML

<UserControl x:Class="DeviceView.CameraStreamView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:ffme="clr-namespace:Unosquare.FFME;assembly=ffme.win"
             mc:Ignorable="d" 
             d:DesignHeight="200" d:DesignWidth="267">

    <Grid>
        <ffme:MediaElement  Grid.Row="0" x:Name="Media" Background="Black" LoadedBehavior="Play" 
                            UnloadedBehavior="Manual"/>
    </Grid>
</UserControl>

C

public partial class CameraStreamView
{
    public CameraStreamView()
    {
        Unosquare.FFME.Library.FFmpegDirectory = @"Resources\\FFMpeg\\bin";

        InitializeComponent();

        DataContextChanged += OnDataContextChanged;
        Media.MediaFailed += MediaOnMediaFailed;
    }

    private void MediaOnMediaFailed(object sender, MediaFailedEventArgs e)
    {
        MessageHandling.SendInfo($"{e.ErrorException.Message}");
    }

    private void ChangeMediaSource(Uri newSource)
    {
        Media.Source = newSource
        Media.ChangeMedia();
    }
}

[jglk]

Upgrading .NET Framework to 4.7+ should help. Related issue: https://github.com/Ruslan-B/FFmpeg.AutoGen/issues/119

[Gikerl]

@jglk Thanks, I will try that and see if that fixes the issue. I'll report the result back.

[mariodivece]

Any feedback here before I close?

[Gikerl]

I did not have time to update the project quite yet. I will try to get it done this week and report back!

[PhilJenson]

I have the same problem on Windows 7 & Windows 8 with .net 4.6.1 installed. Installing .net 4.7.1 solves it.

However, our project currently targets .net 4.6.1 which means, when we release an update, this will not work on customers who do not have .net 4.7.1.

As this seems to relate to FFmpeg.AutoGen, in the absence of a fix here, I guess I am going to have to place a warning message in the app to tell customers to upgrade .net. Not ideal.

[Gikerl]

Upgrading to .Net 4.8 fixed the issue.

This means we now have to ship and installer that includes the .Net 4.8 framework.

Edit: Upgrading to .Net Framework 4.8 sadly does not work as there is a known Nuget bug that doesn't copy all referenced dlls to the build directory (https://github.com/NuGet/Home/issues/7440)

Is there another solution for .Net 4.6.2?

[mariodivece]

Unsure how to fix this for FFME specifically. Have you tried filing an issue in the https://github.com/Ruslan-B/FFmpeg.AutoGen project?