lavfi/fieldorder: work with non writtable frames too

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_fieldorder.c

@@ -80,21 +80,35 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
     AVFilterContext   *ctx     = inlink->dst;
     FieldOrderContext *s       = ctx->priv;
     AVFilterLink      *outlink = ctx->outputs[0];
-    int h, plane, line_step, line_size, line;
-    uint8_t *data;
+    int h, plane, src_line_step, dst_line_step, line_size, line;
+    uint8_t *dst, *src;
+    AVFrame *out;
 
     if (!frame->interlaced_frame ||
         frame->top_field_first == s->dst_tff)
         return ff_filter_frame(outlink, frame);
 
+    if (av_frame_is_writable(frame)) {
+        out = frame;
+    } else {
+        out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+        if (!out) {
+            av_frame_free(&frame);
+            return AVERROR(ENOMEM);
+        }
+        av_frame_copy_props(out, frame);
+    }
+
     av_dlog(ctx,
             "picture will move %s one line\n",
             s->dst_tff ? "up" : "down");
     h = frame->height;
     for (plane = 0; plane < 4 && frame->data[plane] && frame->linesize[plane]; plane++) {
-        line_step = frame->linesize[plane];
+        dst_line_step = out->linesize[plane];
+        src_line_step = frame->linesize[plane];
         line_size = s->line_size[plane];
-        data = frame->data[plane];
+        dst = out->data[plane];
+        src = frame->data[plane];
         if (s->dst_tff) {
             /** Move every line up one line, working from
              *  the top to the bottom of the frame.
@@ -103,11 +117,12 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
              *  penultimate line from that field. */
             for (line = 0; line < h; line++) {
                 if (1 + line < frame->height) {
-                    memcpy(data, data + line_step, line_size);
+                    memcpy(dst, src + src_line_step, line_size);
                 } else {
-                    memcpy(data, data - line_step - line_step, line_size);
+                    memcpy(dst, src - 2 * src_line_step, line_size);
                 }
-                data += line_step;
+                dst += dst_line_step;
+                src += src_line_step;
             }
         } else {
             /** Move every line down one line, working from
@@ -115,20 +130,24 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
              *  The original bottom line is lost.
              *  The new first line is created as a copy of the
              *  second line from that field. */
-            data += (h - 1) * line_step;
+            dst += (h - 1) * dst_line_step;
+            src += (h - 1) * src_line_step;
             for (line = h - 1; line >= 0 ; line--) {
                 if (line > 0) {
-                    memcpy(data, data - line_step, line_size);
+                    memcpy(dst, src - src_line_step, line_size);
                 } else {
-                    memcpy(data, data + line_step + line_step, line_size);
+                    memcpy(dst, src + 2 * src_line_step, line_size);
                 }
-                data -= line_step;
+                dst -= dst_line_step;
+                src -= src_line_step;
             }
         }
     }
-    frame->top_field_first = s->dst_tff;
+    out->top_field_first = s->dst_tff;
 
-    return ff_filter_frame(outlink, frame);
+    if (frame != out)
+        av_frame_free(&frame);
+    return ff_filter_frame(outlink, out);
 }
 
 #define OFFSET(x) offsetof(FieldOrderContext, x)
@@ -149,7 +168,6 @@ static const AVFilterPad avfilter_vf_fieldorder_inputs[] = {
         .type             = AVMEDIA_TYPE_VIDEO,
         .config_props     = config_input,
         .filter_frame     = filter_frame,
-        .needs_writable   = 1,
     },
     { NULL }
 };