Fix crash when resizing a video frame for encoding (closes #125, closes

#87)

FFMediaToolkit/Common/Internal/ImageConverter.cs

@@ -1,5 +1,6 @@
 namespace FFMediaToolkit.Common.Internal
 {
+ using System;
  using System.Drawing;
  using FFMediaToolkit.Graphics;
  using FFmpeg.AutoGen;
@@ -9,6 +10,11 @@
  /// </summary>
  internal unsafe class ImageConverter : Wrapper<SwsContext>
  {
+ // sws_scale requires up to 16 extra bytes allocated in the input buffer when resizing an image
+ // (reference: https://www.ffmpeg.org/doxygen/6.0/frame_8h_source.html#l00340)
+ private const int BufferPaddingSize = 16;
+ private byte[] tmpBuffer = { };
+
  private readonly Size destinationSize;
  private readonly AVPixelFormat destinationFormat;
  private Size lastSourceSize;
@@ -34,7 +40,22 @@ public ImageConverter(Size destinationSize, AVPixelFormat destinationFormat)
  internal void FillAVFrame(ImageData bitmap, VideoFrame destinationFrame)
  {
  UpdateContext(bitmap.ImageSize, (AVPixelFormat)bitmap.PixelFormat);
- fixed (byte* ptr = bitmap.Data)
+
+ var requiredBufferLength = (bitmap.Stride * bitmap.ImageSize.Height) + BufferPaddingSize;
+ var shouldUseTmpBuffer = bitmap.ImageSize != destinationSize && bitmap.Data.Length < requiredBufferLength;
+
+ if (shouldUseTmpBuffer)
+ {
+ if (tmpBuffer.Length < requiredBufferLength)
+ {
+ tmpBuffer = new byte[requiredBufferLength];
+ }
+
+ bitmap.Data.CopyTo(tmpBuffer);
+ }
+
+ var source = shouldUseTmpBuffer ? tmpBuffer : bitmap.Data;
+ fixed (byte* ptr = source)
  {
  var data = new byte*[4] { ptr, null, null, null };
  var linesize = new int[4] { bitmap.Stride, 0, 0, 0 };

FFMediaToolkit/Graphics/ImageData.cs

@@ -22,7 +22,7 @@
  public ImageData(Span<byte> data, ImagePixelFormat pixelFormat, Size imageSize)
  {
  var size = EstimateStride(imageSize.Width, pixelFormat) * imageSize.Height;
- if (data.Length != size)
+ if (data.Length < size)
  {
  throw new ArgumentException("Pixel buffer size doesn't match size required by this image format.");
  }