diff --git a/README.md b/README.md
index 1f13e73..fe3633c 100644
--- a/README.md
+++ b/README.md
@@ -43,7 +43,7 @@ bitrate = 1440
 ## function
 - support YUY2 or MJPEG format usb camera.
 - support hardware h264 encode.
-- wupport NV12 NV16 NV21 NV61 format mipi csi camera. (test max support 2560x1440)
+- wupport NV12 NV16 NV21 NV61 format mipi csi camera. (test max support 4224x3136)
 
 ## Benefits of improvement
 - RkCamRtspServer cpu usage
diff --git a/src/RkEncoder.cc b/src/RkEncoder.cc
index 2c8ce70..63a78d4 100644
--- a/src/RkEncoder.cc
+++ b/src/RkEncoder.cc
@@ -98,7 +98,7 @@ int RkEncoder::init()
 	 * 40 / 41 / 42         - 1080p@30fps / 1080p@30fps / 1080p@60fps
 	 * 50 / 51 / 52         - 4K@30fps
 	 */
-	mpp_enc_cfg_set_s32(cfg, "h264:level", 40);
+	mpp_enc_cfg_set_s32(cfg, "h264:level", 52);
 	mpp_enc_cfg_set_s32(cfg, "h264:cabac_en", 1);
 	mpp_enc_cfg_set_s32(cfg, "h264:cabac_idc", 0);
 	mpp_enc_cfg_set_s32(cfg, "h264:trans8x8", 1);
diff --git a/src/transcoder.cc b/src/transcoder.cc
index b42d3cc..118b4dd 100644
--- a/src/transcoder.cc
+++ b/src/transcoder.cc
@@ -96,15 +96,17 @@ void TransCoder::init()
 
 void TransCoder::run()
 {
+    uint8_t *buffer;
+    
     timeval tv;
     for (;;) {
         tv.tv_sec = 1;
         tv.tv_usec = 0;
         int startCode = 0;
         int ret = capture->isReadable(&tv);
+        buffer =(uint8_t*) malloc(capture->getBufferSize());
         if (ret == 1) {
-            uint8_t buffer[capture->getBufferSize()];
-            int resize = capture->read((char *)buffer, sizeof(buffer));
+            int resize = capture->read((char *)buffer, capture->getBufferSize());
             frameSize = 0;
             if (config.format == "MJPEG") {
                 ret = decompress->tjpeg2yuv(buffer, resize, &yuv_buf, &yuv_size);
@@ -126,6 +128,7 @@ void TransCoder::run()
 
             if (onEncodedDataCallback && frameSize > 0) {
                 onEncodedDataCallback(std::vector<uint8_t>(encodeData + startCode, encodeData + frameSize));
+                free(buffer);
             }
         } else if (ret == -1) {
             LOG(ERROR, "stop %s", strerror(errno));