GetThumbnailAsync doesn't handle croping and scaling in the same task

[NorfAlrin]

Given a crop and resize applied to a 640x480 video:

var conversionOptions = new ConversionOptions
{
    CustomHeight = 100,
    CustomWidth = 100,
    SourceCrop = new CropRectangle {Width = 480, Height = 480}
};  
await engine.GetThumbnailAsync(mediaFile, outputFile, conversionOptions)

I would expect both the crop and the resize would be applied.

But only the crop is applied.

I suspect this is because the above results in:

ffmpeg.exe -y -ss 1.0 -i input.mov  -vframes 1 -filter:v "crop=480:4809::" -vf "scale=100:100" output.jpg

Rather than:

ffmpeg.exe -y -ss 1.0  -i input.mov  -vframes 1 -filter:v "crop=480:4809::, scale=100:100" output.jpg

With the filters appended together, see https://stackoverflow.com/questions/22523006/how-to-use-filter-and-vf-command-on-ffmpeg

[AaaBin]

I found that VideoSize = VideoSize.Custom should be used to specify a custom size, even when cropping is not enabled