swscale: support internal scaler cascades

Fixes Ticket3170

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 10 insertions, 0 deletions

diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
index 1e53690908..63b4eca829 100644
--- a/libswscale/swscale_internal.h
+++ b/libswscale/swscale_internal.h
@@ -61,6 +61,8 @@
 #   define APCK_SIZE 16
 #endif
 
+#define RETCODE_USE_CASCADE -12345
+
 struct SwsContext;
 
 typedef enum SwsDither {
@@ -301,6 +303,14 @@ typedef struct SwsContext {
     int sliceDir;                 ///< Direction that slices are fed to the scaler (1 = top-to-bottom, -1 = bottom-to-top).
     double param[2];              ///< Input parameters for scaling algorithms that need them.
 
+    /* The cascaded_* fields allow spliting a scaler task into multiple
+     * sequential steps, this is for example used to limit the maximum
+     * downscaling factor that needs to be supported in one scaler.
+     */
+    struct SwsContext *cascaded_context[2];
+    int cascaded_tmpStride[4];
+    uint8_t *cascaded_tmp[4];
+
     uint32_t pal_yuv[256];
     uint32_t pal_rgb[256];