Make sure inputs to sws_scale are aligned, as I think they must be.

2 files changed, 30 insertions, 5 deletions

diff --git a/src/lib/image.cc b/src/lib/image.cc
index 3afb6205e..0a51add00 100644
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -96,11 +96,15 @@ Image::components () const
 }
 
 shared_ptr<Image>
-Image::scale (Size out_size, Scaler const * scaler, bool aligned) const
+Image::scale (Size out_size, Scaler const * scaler, bool result_aligned) const
 {
 	assert (scaler);
+	/* Empirical testing suggests that sws_scale() will crash if
+	   the input image is not aligned.
+	*/
+	assert (aligned ());
 
-	shared_ptr<Image> scaled (new SimpleImage (pixel_format(), out_size, aligned));
+	shared_ptr<Image> scaled (new SimpleImage (pixel_format(), out_size, result_aligned));
 
 	struct SwsContext* scale_context = sws_getContext (
 		size().width, size().height, pixel_format(),
@@ -125,14 +129,18 @@ Image::scale (Size out_size, Scaler const * scaler, bool aligned) const
  *  @param scaler Scaler to use.
  */
 shared_ptr<Image>
-Image::scale_and_convert_to_rgb (Size out_size, int padding, Scaler const * scaler, bool aligned) const
+Image::scale_and_convert_to_rgb (Size out_size, int padding, Scaler const * scaler, bool result_aligned) const
 {
 	assert (scaler);
+	/* Empirical testing suggests that sws_scale() will crash if
+	   the input image is not aligned.
+	*/
+	assert (aligned ());
 
 	Size content_size = out_size;
 	content_size.width -= (padding * 2);
 
-	shared_ptr<Image> rgb (new SimpleImage (PIX_FMT_RGB24, content_size, aligned));
+	shared_ptr<Image> rgb (new SimpleImage (PIX_FMT_RGB24, content_size, result_aligned));
 
 	struct SwsContext* scale_context = sws_getContext (
 		size().width, size().height, pixel_format(),
@@ -153,7 +161,7 @@ Image::scale_and_convert_to_rgb (Size out_size, int padding, Scaler const * scal
 	   scheme of things.
 	*/
 	if (padding > 0) {
-		shared_ptr<Image> padded_rgb (new SimpleImage (PIX_FMT_RGB24, out_size, aligned));
+		shared_ptr<Image> padded_rgb (new SimpleImage (PIX_FMT_RGB24, out_size, result_aligned));
 		padded_rgb->make_black ();
 
 		/* XXX: we are cheating a bit here; we know the frame is RGB so we can
@@ -485,6 +493,12 @@ SimpleImage::size () const
 	return _size;
 }
 
+bool
+SimpleImage::aligned () const
+{
+	return _aligned;
+}
+
 FilterBufferImage::FilterBufferImage (AVPixelFormat p, AVFilterBufferRef* b)
 	: Image (p)
 	, _buffer (b)
@@ -522,6 +536,13 @@ FilterBufferImage::size () const
 	return Size (_buffer->video->w, _buffer->video->h);
 }
 
+bool
+FilterBufferImage::aligned () const
+{
+	/* XXX? */
+	return true;
+}
+
 RGBPlusAlphaImage::RGBPlusAlphaImage (shared_ptr<const Image> im)
 	: SimpleImage (im->pixel_format(), im->size(), false)
 {
diff --git a/src/lib/image.h b/src/lib/image.h
index 5ca3f337c..23f13a648 100644
--- a/src/lib/image.h
+++ b/src/lib/image.h
@@ -68,6 +68,8 @@ public:
 	/** @return Size of the image, in pixels */
 	virtual libdcp::Size size () const = 0;
 
+	virtual bool aligned () const = 0;
+
 	int components () const;
 	int lines (int) const;
 
@@ -107,6 +109,7 @@ public:
 	int * line_size () const;
 	int * stride () const;
 	libdcp::Size size () const;
+	bool aligned () const;
 
 private:
 	/* Not allowed */
@@ -131,6 +134,7 @@ public:
 	int * line_size () const;
 	int * stride () const;
 	libdcp::Size size () const;
+	bool aligned () const;
 
 protected:
 	void allocate ();