avfilter/vf_yadif: reallocate frames if strides differ

Fixes Ticket2896

An alternative to this would be to change the code to support any
stride.
The condition of differing strides should be rare.
If theres no speedloss supporting any stride would be better
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_yadif.c

@@ -22,6 +22,7 @@
 #include "libavutil/common.h"
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
+#include "libavutil/imgutils.h"
 #include "avfilter.h"
 #include "formats.h"
 #include "internal.h"
@@ -285,6 +286,29 @@ static int return_frame(AVFilterContext *ctx, int is_second)
     return ret;
 }
 
+static int checkstride(YADIFContext *yadif, const AVFrame *a, const AVFrame *b)
+{
+    int i;
+    for (i = 0; i < yadif->csp->nb_components; i++)
+        if (a->linesize[i] != b->linesize[i])
+            return 1;
+    return 0;
+}
+
+static void fixstride(AVFilterLink *link, AVFrame *f)
+{
+    AVFrame *dst = ff_default_get_video_buffer(link, f->width, f->height);
+    if(!dst)
+        return;
+    av_frame_copy_props(dst, f);
+    av_image_copy(dst->data, dst->linesize,
+                  f->data, f->linesize,
+                  dst->format, dst->width, dst->height);
+    av_frame_unref(f);
+    av_frame_move_ref(f, dst);
+    av_frame_free(&dst);
+}
+
 static int filter_frame(AVFilterLink *link, AVFrame *frame)
 {
     AVFilterContext *ctx = link->dst;
@@ -304,6 +328,19 @@ static int filter_frame(AVFilterLink *link, AVFrame *frame)
     if (!yadif->cur)
         return 0;
 
+    if (checkstride(yadif, yadif->next, yadif->cur)) {
+        av_log(ctx, AV_LOG_VERBOSE, "Reallocating frame due to differing stride\n");
+        fixstride(link, yadif->next);
+    }
+    if (checkstride(yadif, yadif->next, yadif->cur))
+        fixstride(link, yadif->cur);
+    if (yadif->prev && checkstride(yadif, yadif->next, yadif->prev))
+        fixstride(link, yadif->prev);
+    if (checkstride(yadif, yadif->next, yadif->cur) || (yadif->prev && checkstride(yadif, yadif->next, yadif->prev))) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to reallocate frame\n");
+        return -1;
+    }
+
     if ((yadif->deint && !yadif->cur->interlaced_frame) || ctx->is_disabled) {
         yadif->out  = av_frame_clone(yadif->cur);
         if (!yadif->out)