/// <exception cref="DecoderException"></exception>
public static FFmpegDecodedVideoScaler Create(DecodedVideoFrameParameters decodedVideoFrameParameters,
TransformParameters transformParameters)
{
if (decodedVideoFrameParameters == null)
{
throw new ArgumentNullException(nameof(decodedVideoFrameParameters));
}
if (transformParameters == null)
{
throw new ArgumentNullException(nameof(transformParameters));
}
int sourceLeft = 0;
int sourceTop = 0;
int sourceWidth = decodedVideoFrameParameters.Width;
int sourceHeight = decodedVideoFrameParameters.Height;
int scaledWidth = decodedVideoFrameParameters.Width;
int scaledHeight = decodedVideoFrameParameters.Height;
if (!transformParameters.RegionOfInterest.IsEmpty)
{
sourceLeft =
(int)(decodedVideoFrameParameters.Width * transformParameters.RegionOfInterest.Left);
sourceTop =
(int)(decodedVideoFrameParameters.Height * transformParameters.RegionOfInterest.Top);
sourceWidth =
(int)(decodedVideoFrameParameters.Width * transformParameters.RegionOfInterest.Width);
sourceHeight =
(int)(decodedVideoFrameParameters.Height * transformParameters.RegionOfInterest.Height);
}
if (!transformParameters.TargetFrameSize.IsEmpty)
{
scaledWidth = transformParameters.TargetFrameSize.Width;
scaledHeight = transformParameters.TargetFrameSize.Height;
ScalingPolicy scalingPolicy = transformParameters.ScalePolicy;
float srcAspectRatio = (float)sourceWidth / sourceHeight;
float destAspectRatio = (float)scaledWidth / scaledHeight;
if (scalingPolicy == ScalingPolicy.Auto)
{
float relativeChange = Math.Abs(srcAspectRatio - destAspectRatio) / srcAspectRatio;
scalingPolicy = relativeChange > MaxAspectRatioError
? ScalingPolicy.RespectAspectRatio
: ScalingPolicy.Stretch;
}
if (scalingPolicy == ScalingPolicy.RespectAspectRatio)
{
if (destAspectRatio < srcAspectRatio)
{
scaledHeight = sourceHeight * scaledWidth / sourceWidth;
}
else
{
scaledWidth = sourceWidth * scaledHeight / sourceHeight;
}
}
}
PixelFormat scaledPixelFormat = transformParameters.TargetFormat;
FFmpegPixelFormat scaledFFmpegPixelFormat = GetFFmpegPixelFormat(scaledPixelFormat);
FFmpegScalingQuality scaleQuality = GetFFmpegScaleQuality(transformParameters.ScaleQuality);
int resultCode = FFmpegVideoPInvoke.CreateVideoScaler(sourceLeft, sourceTop, sourceWidth, sourceHeight,
decodedVideoFrameParameters.PixelFormat,
scaledWidth, scaledHeight, scaledFFmpegPixelFormat, scaleQuality, out var handle);
if (resultCode != 0)
{
throw new DecoderException(@"An error occurred while creating scaler, code: {resultCode}");
}
return(new FFmpegDecodedVideoScaler(handle, scaledWidth, scaledHeight, scaledPixelFormat));
}
