libx264: support aspect Ratio Switch

libavcodec/libx264.c

@@ -119,6 +119,12 @@ static int X264_frame(AVCodecContext *ctx, uint8_t *buf,
             x4->params.b_tff = frame->top_field_first;
             x264_encoder_reconfig(x4->enc, &x4->params);
         }
+        if (x4->params.vui.i_sar_height != ctx->sample_aspect_ratio.den
+         || x4->params.vui.i_sar_width != ctx->sample_aspect_ratio.num) {
+            x4->params.vui.i_sar_height = ctx->sample_aspect_ratio.den;
+            x4->params.vui.i_sar_width = ctx->sample_aspect_ratio.num;
+            x264_encoder_reconfig(x4->enc, &x4->params);
+        }
     }
 
     do {