diff --git a/3rdparty/libjpeg-turbo/CMakeLists.txt b/3rdparty/libjpeg-turbo/CMakeLists.txt
index 531a00e017681a4aec716d34708ea981906e6cd3..b2c01acbc09673f6c19582591417df205e1c8f1c 100644
--- a/3rdparty/libjpeg-turbo/CMakeLists.txt
+++ b/3rdparty/libjpeg-turbo/CMakeLists.txt
@@ -4,9 +4,9 @@ ocv_warnings_disable(CMAKE_C_FLAGS -Wunused-parameter -Wsign-compare -Wshorten-6
 
 set(VERSION_MAJOR 2)
 set(VERSION_MINOR 0)
-set(VERSION_REVISION 2)
+set(VERSION_REVISION 4)
 set(VERSION ${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_REVISION})
-set(LIBJPEG_TURBO_VERSION_NUMBER 2000002)
+set(LIBJPEG_TURBO_VERSION_NUMBER 2000004)
 
 string(TIMESTAMP BUILD "opencv-${OPENCV_VERSION}-libjpeg-turbo")
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
diff --git a/3rdparty/libjpeg-turbo/README.md b/3rdparty/libjpeg-turbo/README.md
index a769259891ce0ffa8a3d71834e91650186c516eb..e7ff743a471727b5acda7f6db7f40b463e71de2a 100644
--- a/3rdparty/libjpeg-turbo/README.md
+++ b/3rdparty/libjpeg-turbo/README.md
@@ -1,14 +1,14 @@
 Background
 ==========
 
-libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2,
-AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression
-on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG
-compression on x86 and x86-64 systems.  On such systems, libjpeg-turbo is
-generally 2-6x as fast as libjpeg, all else being equal.  On other types of
-systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by
-virtue of its highly-optimized Huffman coding routines.  In many cases, the
-performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.
+libjpeg-turbo is a JPEG image codec that uses SIMD instructions to accelerate
+baseline JPEG compression and decompression on x86, x86-64, ARM, PowerPC, and
+MIPS systems, as well as progressive JPEG compression on x86 and x86-64
+systems.  On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg,
+all else being equal.  On other types of systems, libjpeg-turbo can still
+outperform libjpeg by a significant amount, by virtue of its highly-optimized
+Huffman coding routines.  In many cases, the performance of libjpeg-turbo
+rivals that of proprietary high-speed JPEG codecs.
 
 libjpeg-turbo implements both the traditional libjpeg API as well as the less
 powerful but more straightforward TurboJPEG API.  libjpeg-turbo also features
@@ -135,25 +135,24 @@ without recompiling.  libjpeg-turbo does not claim to support all of the
 libjpeg v7+ features, nor to produce identical output to libjpeg v7+ in all
 cases (see below.)
 
-By passing an argument of `--with-jpeg7` or `--with-jpeg8` to `configure`, or
-an argument of `-DWITH_JPEG7=1` or `-DWITH_JPEG8=1` to `cmake`, you can build a
-version of libjpeg-turbo that emulates the libjpeg v7 or v8 ABI, so that
-programs that are built against libjpeg v7 or v8 can be run with libjpeg-turbo.
-The following section describes which libjpeg v7+ features are supported and
-which aren't.
+By passing an argument of `-DWITH_JPEG7=1` or `-DWITH_JPEG8=1` to `cmake`, you
+can build a version of libjpeg-turbo that emulates the libjpeg v7 or v8 ABI, so
+that programs that are built against libjpeg v7 or v8 can be run with
+libjpeg-turbo.  The following section describes which libjpeg v7+ features are
+supported and which aren't.
 
 ### Support for libjpeg v7 and v8 Features
 
 #### Fully supported
 
-- **libjpeg: IDCT scaling extensions in decompressor**<br>
+- **libjpeg API: IDCT scaling extensions in decompressor**<br>
   libjpeg-turbo supports IDCT scaling with scaling factors of 1/8, 1/4, 3/8,
   1/2, 5/8, 3/4, 7/8, 9/8, 5/4, 11/8, 3/2, 13/8, 7/4, 15/8, and 2/1 (only 1/4
   and 1/2 are SIMD-accelerated.)
 
-- **libjpeg: Arithmetic coding**
+- **libjpeg API: Arithmetic coding**
 
-- **libjpeg: In-memory source and destination managers**<br>
+- **libjpeg API: In-memory source and destination managers**<br>
   See notes below.
 
 - **cjpeg: Separate quality settings for luminance and chrominance**<br>
@@ -185,14 +184,14 @@ means of quality improvement.  The reader is invited to peruse the research at
 but it is the general belief of our project that these features have not
 demonstrated sufficient usefulness to justify inclusion in libjpeg-turbo.
 
-- **libjpeg: DCT scaling in compressor**<br>
+- **libjpeg API: DCT scaling in compressor**<br>
   `cinfo.scale_num` and `cinfo.scale_denom` are silently ignored.
   There is no technical reason why DCT scaling could not be supported when
   emulating the libjpeg v7+ API/ABI, but without the SmartScale extension (see
   below), only scaling factors of 1/2, 8/15, 4/7, 8/13, 2/3, 8/11, 4/5, and
   8/9 would be available, which is of limited usefulness.
 
-- **libjpeg: SmartScale**<br>
+- **libjpeg API: SmartScale**<br>
   `cinfo.block_size` is silently ignored.
   SmartScale is an extension to the JPEG format that allows for DCT block
   sizes other than 8x8.  Providing support for this new format would be
@@ -205,7 +204,7 @@ demonstrated sufficient usefulness to justify inclusion in libjpeg-turbo.
   interest in providing this feature would be as a means of supporting
   additional DCT scaling factors.
 
-- **libjpeg: Fancy downsampling in compressor**<br>
+- **libjpeg API: Fancy downsampling in compressor**<br>
   `cinfo.do_fancy_downsampling` is silently ignored.
   This requires the DCT scaling feature, which is not supported.
 
@@ -247,15 +246,14 @@ don't, and it allows those functions to be provided in the "official"
 libjpeg-turbo binaries.
 
 Those who are concerned about maintaining strict conformance with the libjpeg
-v6b or v7 API can pass an argument of `--without-mem-srcdst` to `configure` or
-an argument of `-DWITH_MEM_SRCDST=0` to `cmake` prior to building
-libjpeg-turbo.  This will restore the pre-1.3 behavior, in which
+v6b or v7 API can pass an argument of `-DWITH_MEM_SRCDST=0` to `cmake` prior to
+building libjpeg-turbo.  This will restore the pre-1.3 behavior, in which
 `jpeg_mem_src()` and `jpeg_mem_dest()` are only included when emulating the
 libjpeg v8 API/ABI.
 
 On Un*x systems, including the in-memory source/destination managers changes
-the dynamic library version from 62.1.0 to 62.2.0 if using libjpeg v6b API/ABI
-emulation and from 7.1.0 to 7.2.0 if using libjpeg v7 API/ABI emulation.
+the dynamic library version from 62.2.0 to 62.3.0 if using libjpeg v6b API/ABI
+emulation and from 7.2.0 to 7.3.0 if using libjpeg v7 API/ABI emulation.
 
 Note that, on most Un*x systems, the dynamic linker will not look for a
 function in a library until that function is actually used.  Thus, if a program
@@ -331,7 +329,7 @@ in a way that makes the rest of the libjpeg infrastructure happy, so it is
 necessary to use the slow Huffman decoder when decompressing a JPEG image that
 has restart markers.  This can cause the decompression performance to drop by
 as much as 20%, but the performance will still be much greater than that of
-libjpeg.  Many consumer packages, such as PhotoShop, use restart markers when
+libjpeg.  Many consumer packages, such as Photoshop, use restart markers when
 generating JPEG images, so images generated by those programs will experience
 this issue.
 
@@ -344,3 +342,15 @@ quality of 98-100.  Thus, libjpeg-turbo must use the non-SIMD quantization
 function in those cases.  This causes performance to drop by as much as 40%.
 It is therefore strongly advised that you use the slow integer forward DCT
 whenever encoding images with a JPEG quality of 98 or higher.
+
+
+Memory Debugger Pitfalls
+========================
+
+Valgrind and Memory Sanitizer (MSan) can generate false positives
+(specifically, incorrect reports of uninitialized memory accesses) when used
+with libjpeg-turbo's SIMD extensions.  It is generally recommended that the
+SIMD extensions be disabled, either by passing an argument of `-DWITH_SIMD=0`
+to `cmake` when configuring the build or by setting the environment variable
+`JSIMD_FORCENONE` to `1` at run time, when testing libjpeg-turbo with Valgrind,
+MSan, or other memory debuggers.
diff --git a/3rdparty/libjpeg-turbo/src/jchuff.c b/3rdparty/libjpeg-turbo/src/jchuff.c
index 939b3e76a11e089c666f874e806bb03979d1b205..cb05055d99207bc3a610cc9db415a7b3ea6583bc 100644
--- a/3rdparty/libjpeg-turbo/src/jchuff.c
+++ b/3rdparty/libjpeg-turbo/src/jchuff.c
@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2009-2011, 2014-2016, 2018, D. R. Commander.
+ * Copyright (C) 2009-2011, 2014-2016, 2018-2019, D. R. Commander.
  * Copyright (C) 2015, Matthieu Darbois.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
@@ -43,8 +43,8 @@
  */
 
 /* NOTE: Both GCC and Clang define __GNUC__ */
-#if defined __GNUC__ && (defined __arm__ || defined __aarch64__)
-#if !defined __thumb__ || defined __thumb2__
+#if defined(__GNUC__) && (defined(__arm__) || defined(__aarch64__))
+#if !defined(__thumb__) || defined(__thumb2__)
 #define USE_CLZ_INTRINSIC
 #endif
 #endif
@@ -356,6 +356,8 @@ dump_buffer(working_state *state)
   put_buffer = (put_buffer << size) | code; \
 }
 
+#if SIZEOF_SIZE_T != 8 && !defined(_WIN64)
+
 #define CHECKBUF15() { \
   if (put_bits > 15) { \
     EMIT_BYTE() \
@@ -363,6 +365,8 @@ dump_buffer(working_state *state)
   } \
 }
 
+#endif
+
 #define CHECKBUF31() { \
   if (put_bits > 31) { \
     EMIT_BYTE() \
@@ -428,7 +432,7 @@ dump_buffer(working_state *state)
  * scanning order-- 1, 8, 16, etc.), then this will produce an encoded block
  * larger than 200 bytes.
  */
-#define BUFSIZE  (DCTSIZE2 * 4)
+#define BUFSIZE  (DCTSIZE2 * 8)
 
 #define LOAD_BUFFER() { \
   if (state->free_in_buffer < BUFSIZE) { \
diff --git a/3rdparty/libjpeg-turbo/src/jcmaster.c b/3rdparty/libjpeg-turbo/src/jcmaster.c
index 93b3de68268ee353f00eafcc66b86984a8991781..998dc40a5c968e1c2ebb4286cbf42adba3e9b1e5 100644
--- a/3rdparty/libjpeg-turbo/src/jcmaster.c
+++ b/3rdparty/libjpeg-turbo/src/jcmaster.c
@@ -492,8 +492,8 @@ prepare_for_pass(j_compress_ptr cinfo)
      */
     master->pass_type = output_pass;
     master->pass_number++;
-    /*FALLTHROUGH*/
 #endif
+    /*FALLTHROUGH*/
   case output_pass:
     /* Do a data-output pass. */
     /* We need not repeat per-scan setup if prior optimization pass did it. */
diff --git a/3rdparty/libjpeg-turbo/src/jcphuff.c b/3rdparty/libjpeg-turbo/src/jcphuff.c
index 024d3af0fb15a0b2bed2cb51ee12d669f625c870..8c4efaf16cb686d66c831db69d3ff72ec6d2d39f 100644
--- a/3rdparty/libjpeg-turbo/src/jcphuff.c
+++ b/3rdparty/libjpeg-turbo/src/jcphuff.c
@@ -52,8 +52,8 @@
  */
 
 /* NOTE: Both GCC and Clang define __GNUC__ */
-#if defined __GNUC__ && (defined __arm__ || defined __aarch64__)
-#if !defined __thumb__ || defined __thumb2__
+#if defined(__GNUC__) && (defined(__arm__) || defined(__aarch64__))
+#if !defined(__thumb__) || defined(__thumb2__)
 #define USE_CLZ_INTRINSIC
 #endif
 #endif
diff --git a/3rdparty/libjpeg-turbo/src/jdhuff.c b/3rdparty/libjpeg-turbo/src/jdhuff.c
index 95f38e547e401d3e353100c1db657b924c2f511a..a1128178b0a9bf753d30b5095e9bddf10520e0dc 100644
--- a/3rdparty/libjpeg-turbo/src/jdhuff.c
+++ b/3rdparty/libjpeg-turbo/src/jdhuff.c
@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2009-2011, 2016, 2018, D. R. Commander.
+ * Copyright (C) 2009-2011, 2016, 2018-2019, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -589,7 +589,11 @@ decode_mcu_slow(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
     if (entropy->dc_needed[blkn]) {
       /* Convert DC difference to actual value, update last_dc_val */
       int ci = cinfo->MCU_membership[blkn];
-      s += state.last_dc_val[ci];
+      /* This is really just
+       *   s += state.last_dc_val[ci];
+       * It is written this way in order to shut up UBSan.
+       */
+      s = (int)((unsigned int)s + (unsigned int)state.last_dc_val[ci]);
       state.last_dc_val[ci] = s;
       if (block) {
         /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
@@ -684,7 +688,7 @@ decode_mcu_fast(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 
     if (entropy->dc_needed[blkn]) {
       int ci = cinfo->MCU_membership[blkn];
-      s += state.last_dc_val[ci];
+      s = (int)((unsigned int)s + (unsigned int)state.last_dc_val[ci]);
       state.last_dc_val[ci] = s;
       if (block)
         (*block)[0] = (JCOEF)s;
diff --git a/3rdparty/libjpeg-turbo/src/jdmerge.c b/3rdparty/libjpeg-turbo/src/jdmerge.c
index b3fec04f71e59d8f9319ba27694296553564533b..dff5a350870cc4740a7e5b22ead53ae1129c76c2 100644
--- a/3rdparty/libjpeg-turbo/src/jdmerge.c
+++ b/3rdparty/libjpeg-turbo/src/jdmerge.c
@@ -429,8 +429,6 @@ h2v2_merged_upsample(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
 #define PACK_TWO_PIXELS_LE(l, r)    ((r << 16) | l)
 #define PACK_TWO_PIXELS_BE(l, r)    ((l << 16) | r)
 
-#define PACK_NEED_ALIGNMENT(ptr)    (((size_t)(ptr)) & 3)
-
 #define WRITE_TWO_PIXELS_LE(addr, pixels) { \
   ((INT16 *)(addr))[0] = (INT16)(pixels); \
   ((INT16 *)(addr))[1] = (INT16)((pixels) >> 16); \
diff --git a/3rdparty/libjpeg-turbo/src/jdsample.c b/3rdparty/libjpeg-turbo/src/jdsample.c
index 52ee9af49b36791e01e076f24fe5147f4eb12f3f..50a68b30131890bec2f56e350b4eda25aa66fd5b 100644
--- a/3rdparty/libjpeg-turbo/src/jdsample.c
+++ b/3rdparty/libjpeg-turbo/src/jdsample.c
@@ -8,6 +8,7 @@
  * Copyright (C) 2010, 2015-2016, D. R. Commander.
  * Copyright (C) 2014, MIPS Technologies, Inc., California.
  * Copyright (C) 2015, Google, Inc.
+ * Copyright (C) 2019, Arm Limited.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -315,9 +316,9 @@ h1v2_fancy_upsample(j_decompress_ptr cinfo, jpeg_component_info *compptr,
   JSAMPARRAY output_data = *output_data_ptr;
   JSAMPROW inptr0, inptr1, outptr;
 #if BITS_IN_JSAMPLE == 8
-  int thiscolsum;
+  int thiscolsum, bias;
 #else
-  JLONG thiscolsum;
+  JLONG thiscolsum, bias;
 #endif
   JDIMENSION colctr;
   int inrow, outrow, v;
@@ -327,15 +328,18 @@ h1v2_fancy_upsample(j_decompress_ptr cinfo, jpeg_component_info *compptr,
     for (v = 0; v < 2; v++) {
       /* inptr0 points to nearest input row, inptr1 points to next nearest */
       inptr0 = input_data[inrow];
-      if (v == 0)               /* next nearest is row above */
+      if (v == 0) {             /* next nearest is row above */
         inptr1 = input_data[inrow - 1];
-      else                      /* next nearest is row below */
+        bias = 1;
+      } else {                  /* next nearest is row below */
         inptr1 = input_data[inrow + 1];
+        bias = 2;
+      }
       outptr = output_data[outrow++];
 
       for (colctr = 0; colctr < compptr->downsampled_width; colctr++) {
         thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
-        *outptr++ = (JSAMPLE)((thiscolsum + 1) >> 2);
+        *outptr++ = (JSAMPLE)((thiscolsum + bias) >> 2);
       }
     }
     inrow++;
diff --git a/3rdparty/libjpeg-turbo/src/jfdctint.c b/3rdparty/libjpeg-turbo/src/jfdctint.c
index c0391a92beeef9784c91940203a3174f0754aa18..b47c3061ac5693bcbefb657a4b3690cc047bf58f 100644
--- a/3rdparty/libjpeg-turbo/src/jfdctint.c
+++ b/3rdparty/libjpeg-turbo/src/jfdctint.c
@@ -1,7 +1,7 @@
 /*
  * jfdctint.c
  *
- * This file was part of the Independent JPEG Group's software.
+ * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2015, D. R. Commander.
diff --git a/3rdparty/libjpeg-turbo/src/jidctint.c b/3rdparty/libjpeg-turbo/src/jidctint.c
index 55573429f1ae319b4f0b29921b2a65b076a6075b..98425d5fd083f22c09d84b213c623753826c5093 100644
--- a/3rdparty/libjpeg-turbo/src/jidctint.c
+++ b/3rdparty/libjpeg-turbo/src/jidctint.c
@@ -1,7 +1,7 @@
 /*
  * jidctint.c
  *
- * This file was part of the Independent JPEG Group's software.
+ * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1998, Thomas G. Lane.
  * Modification developed 2002-2009 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
diff --git a/3rdparty/libjpeg-turbo/src/jidctred.c b/3rdparty/libjpeg-turbo/src/jidctred.c
index 1ff352f875ffafdc8d38987e216d7830acb906b2..1dd65a94d975176c4ab6cda797a971f8eac9875f 100644
--- a/3rdparty/libjpeg-turbo/src/jidctred.c
+++ b/3rdparty/libjpeg-turbo/src/jidctred.c
@@ -1,7 +1,7 @@
 /*
  * jidctred.c
  *
- * This file was part of the Independent JPEG Group's software.
+ * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1998, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2015, D. R. Commander.