* Bug fix for issue #14: Duplicate error events

[dm413]

See #14
When ffmpeg.exe reports an error (via a non-zero exit code), this library raised the Error event twice with the same message. Changed to only raise the event once.

[cmxl]

Why does it trigger the event twice?
I need to look into this one again.
But maybe you could elaborate on that one meanwhile.

[cmxl]

Is it possible that this is an issue when cancelling the ffmpegprocess?
Have you ever encountered any other form of duplicate exceptions?
Would be great to have something reproducible and some simple tests to confirm.

Can you think of any situation where there was no ffmpeg error, but the process would have ended with and exitcode other than 0?

If it is readlly only when we cancelled the task, we should maybe check if the exitcode AND if a cancellation was requested here

FFmpeg.NET/src/FFmpeg.NET/Extensions/ProcessExtensions.cs

Line 44 in 82f1c83

if (process.ExitCode != 0)

[dm413]

This has nothing to do with cancellation. It occurs on all errors from ffmpeg.exe.

The relevant code is in FFmpegProcess.ExecuteAsync()

await ffmpegProcess.WaitForExitAsync((exitCode) => OnException(messages, parameters, exitCode, caughtException), cancellationToken);
if (caughtException != null || ffmpegProcess.ExitCode != 0)
{
    OnException(messages, parameters, ffmpegProcess.ExitCode, caughtException);
}

The lamba expression gets passed to ProcessExtension.WaitForExitAsync(), which does:

if (process.ExitCode != 0)
    onException?.Invoke(process.ExitCode);

If the exit code is non-zero:

1. The lambda expression passed to WaitForExitAsync will call OnException.
2. The if statement will also call OnException

Unfortunately I am not familiar with XUnit. I played around with it for a while but didn't get anywhere. Running the FFmpeg.NET.Tests project just flashes a command window and exits. Google results say to run xunit.console, but that exe doesn't seem to be installed anywhere. Can you point me at a source of information about how to write and run tests?

[cmxl]

dotnet sdk includes the xunit testrunner by default.
you could also run those tests via cmd -> dotnet test FFmpeg.NET.Tests.csproj

Edit:
This could help you @dm413: #18