# VideoWriter\_IntelMFX: Written file is not playable

**URL:** <https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182>\
**Category:** C++\
**Tags:** videoio\
**Created:** [September 13, 2022, 1:52pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182 "2022-09-13T13:52:02Z")\
**Posts on this page:** 18\
**Page:** 1

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 1:52pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/1 "2022-09-13T13:52:02Z")

</div>

Hello,

i run OpenCV 4.5.4 on Windows 10 x64 21H2. I compiled it from source with the Intel Media SDK MSDK2021R1.exe.

In my application i grab files and write them to HDD as a video file. I open it as following:

```auto
			p_writer->open("video.mp4",
						   cv::VideoWriter::fourcc('A', 'V', 'C', ' '),
						   file_fps, frame_size,
				{
					cv::VIDEOWRITER_PROP_HW_ACCELERATION, cv::VIDEO_ACCELERATION_MFX,
					cv::VIDEOWRITER_PROP_HW_DEVICE, -1
				});
```

I write as following:

```auto
		if (p_writer && p_writer->isOpened())
		{
			*p_writer << current_frame.GetMat();
		}
```

When i step into the write function i can see that the VideoWriter\_IntelMFX::write\_one() function is used and the file is extended. But the video file is not playable. With ffmpeg i can check it, there is the codec indicated but it reports no duration… Visual Studios Binary Editor shows that there is “random data” in the file…

```auto
ffmpeg version 2022-09-12-git-3ce6fa6b6d-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 12.1.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil 57. 36.101 / 57. 36.101
  libavcodec 59. 43.100 / 59. 43.100
  libavformat 59. 31.100 / 59. 31.100
  libavdevice 59. 8.101 / 59. 8.101
  libavfilter 8. 48.100 / 8. 48.100
  libswscale 6. 8.112 / 6. 8.112
  libswresample 4. 9.100 / 4. 9.100
  libpostproc 56. 7.100 / 56. 7.100
Input #0, h264, from 'video.mp4':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 1280x940 [SAR 1:1 DAR 64:47], 29 fps, 29 tbr, 1200k tbn
```

For completeness the cmake configuration output. If i use the ffmpeg backend it works and the video is playable. I just played aroud with the container format and the codec. The MFX writer seem to support MPG2, H264, H265, AVC , HEVC codec (from the source).

Any help would be appreceated …

```auto
Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.19044.
Detected processor: AMD64
Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE) (Required is at least version "2.7")
Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE) (Required is at least version "3.2")
libjpeg-turbo: VERSION = 2.1.0, BUILD = opencv-4.5.4-libjpeg-turbo
Could NOT find OpenJPEG (minimal suitable version: 2.0, recommended version >= 2.3.1). OpenJPEG will be built from sources
OpenJPEG: VERSION = 2.4.0, BUILD = opencv-4.5.4-openjp2-2.4.0
OpenJPEG libraries will be built from sources: libopenjp2 (version "2.4.0")
found Intel IPP (ICV version): 2020.0.0 [2020.0.0 Gold]
at: C:/Daten/Entwicklung/3rdParty/OpenCV/build/3rdparty/ippicv/ippicv_win/icv
found Intel IPP Integration Wrappers sources: 2020.0.0
at: C:/Daten/Entwicklung/3rdParty/OpenCV/build/3rdparty/ippicv/ippicv_win/iw
Could not find OpenBLAS include. Turning OpenBLAS_FOUND off
Could not find OpenBLAS lib. Turning OpenBLAS_FOUND off
Could NOT find BLAS (missing: BLAS_LIBRARIES) 
Could NOT find LAPACK (missing: LAPACK_LIBRARIES) 
    Reason given by package: LAPACK could not be found because dependency BLAS could not be found.

Could NOT find JNI (missing: JAVA_AWT_LIBRARY JAVA_JVM_LIBRARY JAVA_INCLUDE_PATH JAVA_INCLUDE_PATH2 JAVA_AWT_INCLUDE_PATH) 
VTK is not found. Please set -DVTK_DIR in CMake to VTK build directory, or to VTK install subdirectory with VTKConfig.cmake file
ADE: Download: v0.1.1f.zip
Try 1 failed
CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  ADE: Download failed: 28;"Timeout was reached"

  For details please refer to the download log file:

  C:/Daten/Entwicklung/3rdParty/OpenCV/build/CMakeDownloadLog.txt

Call Stack (most recent call first):
  modules/gapi/cmake/DownloadADE.cmake:5 (ocv_download)
  modules/gapi/cmake/init.cmake:19 (include)
  cmake/OpenCVModule.cmake:298 (include)
  cmake/OpenCVModule.cmake:361 (_add_modules_1)
  cmake/OpenCVModule.cmake:385 (ocv_glob_modules)
  CMakeLists.txt:917 (ocv_register_modules)

OpenCV Python: during development append to PYTHONPATH: C:/Daten/Entwicklung/3rdParty/OpenCV/build/python_loader
Allocator metrics storage type: 'long long'
Registering hook 'INIT_MODULE_SOURCES_opencv_dnn': C:/Daten/Entwicklung/3rdParty/OpenCV/upstream/modules/dnn/cmake/hooks/INIT_MODULE_SOURCES_opencv_dnn.cmake
opencv_dnn: filter out cuda4dnn source code
Excluding from source files list: <BUILD>/modules/dnn/layers/layers_common.rvv.cpp
highgui: using builtin backend: WIN32UI

General configuration for OpenCV 4.5.4 =====================================
  Version control: 4.5.4

  Platform:
    Timestamp: 2022-08-22T09:01:37Z
    Host: Windows 10.0.19044 AMD64
    CMake: 3.21.0
    CMake generator: Visual Studio 16 2019
    CMake build tool: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/MSBuild/Current/Bin/MSBuild.exe
    MSVC: 1929
    Configuration: Debug Release

  CPU/HW features:
    Baseline: SSE SSE2 SSE3
      requested: SSE3
    Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
      requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
      SSE4_1 (16 files): + SSSE3 SSE4_1
      SSE4_2 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (5 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (31 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (8 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX

  C/C++:
    Built as dynamic libs?: YES
    C++ standard: 11
    C++ Compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.29.30133/bin/Hostx64/x64/cl.exe (ver 19.29.30139.0)
    C++ flags (Release): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP /MD /O2 /Ob2 /DNDEBUG 
    C++ flags (Debug): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP /MDd /Zi /Ob0 /Od /RTC1 
    C Compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.29.30133/bin/Hostx64/x64/cl.exe
    C flags (Release): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /MP /MD /O2 /Ob2 /DNDEBUG 
    C flags (Debug): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /MP /MDd /Zi /Ob0 /Od /RTC1 
    Linker flags (Release): /machine:x64 /INCREMENTAL:NO 
    Linker flags (Debug): /machine:x64 /debug /INCREMENTAL 
    ccache: NO
    Precompiled headers: YES
    Extra dependencies:
    3rdparty dependencies:

  OpenCV modules:
    To be built: calib3d core dnn features2d flann highgui imgcodecs imgproc ml objdetect photo stitching ts video videoio
    Disabled: world
    Disabled by dependency: -
    Unavailable: gapi java python2 python3
    Applications: tests perf_tests apps
    Documentation: NO
    Non-free algorithms: NO

  Windows RT support: NO

  GUI: WIN32UI
    Win32 UI: YES
    VTK support: NO

  Media I/O: 
    ZLib: build (ver 1.2.11)
    JPEG: build-libjpeg-turbo (ver 2.1.0-62)
    WEBP: build (ver encoder: 0x020f)
    PNG: build (ver 1.6.37)
    TIFF: build (ver 42 - 4.2.0)
    JPEG 2000: build (ver 2.4.0)
    OpenEXR: build (ver 2.3.0)
    HDR: YES
    SUNRASTER: YES
    PXM: YES
    PFM: YES

  Video I/O:
    DC1394: NO
    FFMPEG: YES (prebuilt binaries)
      avcodec: YES (58.134.100)
      avformat: YES (58.76.100)
      avutil: YES (56.70.100)
      swscale: YES (5.9.100)
      avresample: YES (4.0.0)
    GStreamer: NO
    DirectShow: YES
    Media Foundation: YES
      DXVA: YES
    Intel Media SDK: YES (C:/Program Files (x86)/IntelSWTools/Intel(R) Media SDK 2021 R1/Software Development Kit/lib/x64/libmfx_vs2015.lib)

  Parallel framework: Concurrency

  Trace: YES (with Intel ITT)

  Other third-party libraries:
    Intel IPP: 2020.0.0 Gold [2020.0.0]
           at: C:/Daten/Entwicklung/3rdParty/OpenCV/build/3rdparty/ippicv/ippicv_win/icv
    Intel IPP IW: sources (2020.0.0)
              at: C:/Daten/Entwicklung/3rdParty/OpenCV/build/3rdparty/ippicv/ippicv_win/iw
    Lapack: NO
    Eigen: NO
    Custom HAL: NO
    Protobuf: build (3.5.1)

  OpenCL: YES (NVD3D11)
    Include path: C:/Daten/Entwicklung/3rdParty/OpenCV/upstream/3rdparty/include/opencl/1.2
    Link libraries: Dynamic load

  Python (for build): NO

  Java:                          
    ant: NO
    JNI: NO
    Java wrappers: NO
    Java tests: NO

  Install to: C:/Daten/Entwicklung/3rdParty/OpenCV/4.5.4/x64
-----------------------------------------------------------------

Configuring done
Generating done
```

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 1:59pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/2 "2022-09-13T13:59:50Z")

</div>

I also realized, that i can reencode it with ffmpeg then it is playable in VLC and the Windows Media Player…

---

<div class="post-metadata">

**Author:** ![cudawarped](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@cudawarped](https://forum.opencv.org/u/cudawarped)\
**Post date:** [September 13, 2022, 3:14pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/3 "2022-09-13T15:14:09Z")

</div>

If you give it the correct extention, i.e. .h264 vlc may be able to play it. If I label a raw .h264 file as .mp4 then vlc cannot play it either because it has no idea which codec is used.

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 3:23pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/4 "2022-09-13T15:23:04Z")

</div>

Thanks, i already tried that but no success ☹

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 3:33pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/5 "2022-09-13T15:33:24Z")

</div>

Maybe I need to upgrade vlc… I got vlc 3.0.x

---

<div class="post-metadata">

**Author:** ![cudawarped](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@cudawarped](https://forum.opencv.org/u/cudawarped)\
**Post date:** [September 13, 2022, 3:43pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/6 "2022-09-13T15:43:49Z")

</div>

I doubt it what does ffmpeg list as the codec for the file?

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 4:02pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/7 "2022-09-13T16:02:38Z")

</div>

```auto
Input #0, h264, from 'video.mp4':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 1280x940 [SAR 1:1 DAR 64:47], 29 fps, 29 tbr, 1200k tbn

```

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [September 13, 2022, 4:11pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/8 "2022-09-13T16:11:01Z")

</div>

code please ([[mre]](https://stackoverflow.com/help/minimal-reproducible-example))

are you calling the `release()` method?

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 13, 2022, 4:15pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/9 "2022-09-13T16:15:22Z")

</div>

Yes, its is a std::unique\_ptr\<\>. It calls the destructor when the application ends. I can tommorrow supply a MRE.

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [September 13, 2022, 6:56pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/10 "2022-09-13T18:56:25Z")

</div>

I’m asking if _you_ call the release() method _explicitly_, because you must. try it.

and still, without a [[mre]](https://stackoverflow.com/help/minimal-reproducible-example) nobody can debug your code for you.

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 14, 2022, 5:04am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/11 "2022-09-14T05:04:09Z")

</div>

[https://docs.opencv.org/4.5.4/dd/d9e/classcv\_1\_1VideoWriter.html#aea9c6764cf067ff7af2576267d39c76c](https://docs.opencv.org/4.5.4/dd/d9e/classcv_1_1VideoWriter.html#aea9c6764cf067ff7af2576267d39c76c)

The documentation states that the destructor does that but for the MRE i added an explicit call to release().

ffmpeg shows the same message as with my main application:

```auto
Input #0, h264, from 'video_0.mp4':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 640x480 [SAR 1:1 DAR 4:3], 30 fps, 30 tbr, 1200k tbn
```

Here it is.

```auto
#include <opencv2/videoio.hpp>

#include <string>
#include <memory>

std::string FileName(size_t idx)
{
	std::string fname = "video_" + std::to_string(idx);	
	return fname + ".mp4";
}

void Run(size_t idx, size_t MaxFrames)
{
	int file_fps = 30;

	auto p_cam = std::make_unique<cv::VideoCapture>();
	auto p_writer = std::make_unique<cv::VideoWriter>();

	while (p_cam && p_writer && MaxFrames > 0)
	{
		if (!p_cam->isOpened())
		{
			p_cam->open(0);
		}

		cv::Mat frame;
		*p_cam >> frame;

		if (!p_writer->isOpened())
		{
			cv::Size frame_size = frame.size();

			p_writer->open(FileName(idx),
				cv::VideoWriter::fourcc('H', '2', '6', '4'),
				file_fps, frame_size
				,
				{
					cv::VIDEOWRITER_PROP_HW_ACCELERATION, cv::VIDEO_ACCELERATION_MFX,
					cv::VIDEOWRITER_PROP_HW_DEVICE, -1
				});
		}
		if (p_writer->isOpened())
		{
			*p_writer << frame;
			--MaxFrames;
		}
	}

	if (p_writer)
	{
		p_writer->release();
	}
}

int main(int argc, char** argv)
{
	for (size_t i = 0; i < 3; ++i)
	{
		Run(i, 300);
	}
}
```

Thats the callstack into the VideoWriter\_IntelMfx::write\_one() function

```auto
|>|opencv_videoio454d.dll!VideoWriter_IntelMFX::write_one(const cv::debug_build_guard::_InputArray & bgr) Zeile 192|C++|
|---|---|---|
| |opencv_videoio454d.dll!VideoWriter_IntelMFX::write(const cv::debug_build_guard::_InputArray & input) Zeile 187|C++|
| |opencv_videoio454d.dll!cv::VideoWriter::write(const cv::debug_build_guard::_InputArray & image) Zeile 676|C++|
| |opencv_videoio454d.dll!cv::VideoWriter::operator<<(const cv::Mat & image) Zeile 684|C++|
| |MfxMRE.exe!Run(unsigned __int64 idx, unsigned__ int64 MaxFrames) Zeile 46|C++|
| |MfxMRE.exe!main(int argc, char * * argv) Zeile 61|C++|

```

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 14, 2022, 5:13am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/12 "2022-09-14T05:13:32Z")

</div>

Playing h264 folowwing that tutorial doesnt work either ☹

> **[How to Play H.264 Files in VLC: Step-by-Step Guide with Videos - Reolink Blog](https://reolink.com/blog/how-to-play-h264-files-in-vlc/)**
>
> Stuck in playing H.264 files in VLC? Learn how to play, view and open H.264 codec files on VLC from your PC and Mac from this step-by-step guide.

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 14, 2022, 6:17am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/13 "2022-09-14T06:17:22Z")

</div>

Just upgraded to OpenCV 4.5.5 … no change … ☹

EDIT:  
FYI: I got it working with 4.5.4. The key was to read the tests.

> <https://github.com/opencv/opencv/blob/4.x/modules/videoio/test/test_mfx.cpp>

It has the file ending like .265 and the codec H265. Then VLC could open the file. the H264 i could not get working.

```auto
#include <opencv2/videoio.hpp>

#include <string>
#include <memory>
#include <iostream>

std::string FileName(size_t idx)
{
	std::string fname = "video_" + std::to_string(idx);	
	return fname + ".265";
}
int OurFourCC()
{
	return cv::VideoWriter::fourcc('H', '2', '6', '5');
}

void Run(size_t idx, size_t MaxFrames)
{
	int file_fps = 30;

	auto p_cam = std::make_unique<cv::VideoCapture>();
	auto p_writer = std::make_unique<cv::VideoWriter>();

	while (p_cam && p_writer && MaxFrames > 0)
	{
		if (!p_cam->isOpened())
		{
			p_cam->open(0);
		}

		cv::Mat frame;
		*p_cam >> frame;

		if (!p_writer->isOpened())
		{
			cv::Size frame_size = frame.size();

			p_writer->open(FileName(idx), 
				OurFourCC(),
				file_fps, frame_size
				,
				{
					cv::VIDEOWRITER_PROP_HW_ACCELERATION, cv::VIDEO_ACCELERATION_MFX,
					cv::VIDEOWRITER_PROP_HW_DEVICE, -1
				});

			std::cout << "Writer Backend: " << p_writer->getBackendName() << "\n";
		}
		if (p_writer->isOpened())
		{
			*p_writer << frame;
			--MaxFrames;
		}
	}

	if (p_writer)
	{
		p_writer->release();
	}
}

int main(int argc, char** argv)
{
	for (size_t i = 0; i < 3; ++i)
	{
		Run(i, 300);
	}
}
```

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 14, 2022, 8:47am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/14 "2022-09-14T08:47:09Z")

</div>

> **[MediaSDK encode decode backend](https://github.com/opencv/opencv/wiki/MediaSDK-encode-decode-backend)**
>
> Open Source Computer Vision Library. Contribute to opencv/opencv development by creating an account on GitHub.

> [@](#):
>
> ### Decoding
> 
> Media containers are not supported yet, so it is only possible to decode raw video stream stored in a file. It can be extracted from a container manually using the FFmpeg tool ([source1](https://stackoverflow.com/questions/19300350/extracting-h264-raw-video-stream-from-mp4-or-flv-with-ffmpeg-generate-an-invalid), [source2](https://superuser.com/questions/678897/extract-hevc-bitstream-with-ffmpeg)) or any other tools:

But is is also true for the encoder?

---

<div class="post-metadata">

**Author:** ![cudawarped](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@cudawarped](https://forum.opencv.org/u/cudawarped)\
**Post date:** [September 14, 2022, 10:13am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/15 "2022-09-14T10:13:47Z")

</div>

> [@schorsch\_76](#):
>
> But is is also true for the encoder?

Whilst I have not tried this myself the documentation

> Where `fourcc` can be one of `MPG2`, `H264`, `X264`, `AVC `, `H265` or `HEVC`

would imply this, which is why it doesn’t make sense for the output file to have a .mp4 extension. I am supprised that you had to change the output file name to “.h264” instead of simply changing the extension from “.mp4” to “.h264” once the file was written. I guess internally OpenCV is adding something to the file when you specify a “.mp4” extension.

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [September 14, 2022, 10:52am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/16 "2022-09-14T10:52:44Z")

</div>

ffmpeg is supposed to do all the work, _usually_, but that usually means CPU-only encode/decode. I don’t know if the ffmpeg backend can do hardware acceleration (maybe). MFX is something I know of but have never actually seen used by OpenCV.

the mp4 _container_ is capable of carrying H.264 and H.265 streams. it does however _require_ finalizing (adding indices, updating headers), like most container formats.

if ffmpeg were used, it wouldn’t have liked the `"H264"` fourcc. it prefers `"avc1"`.

I would highly recommend stripping those “smart” pointers out of the program entirely. those are local variables.

And you must check `isOpened()` before doing any reading/writing. and you must NOT assume that `open()` will always succeed. if you open() and then !isOpened(), that is fatal. and you must not assume that reading a frame will always succeed. you must test whether it’s empty. if it is, all you can do is break the loop.

I am not in a position to use MFX but MSMF (picked by VIDEO\_ACCELERATION\_ANY), if told to write a “.mp4”, is perfectly happy to do everything… so the code seems mostly okay in principle.

---

<div class="post-metadata">

**Author:** ![cudawarped](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@cudawarped](https://forum.opencv.org/u/cudawarped)\
**Post date:** [September 14, 2022, 11:30am UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/17 "2022-09-14T11:30:27Z")

</div>

> [@schorsch\_76](#):
>
> But is is also true for the encoder?

Ignore my previous comment I didn’t notice you were using `cv::VIDEO_ACCELERATION_MFX` and not `CAP_INTEL_MFX` see post above instead.

---

<div class="post-metadata">

**Author:** ![schorsch\_76](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@schorsch\_76](https://forum.opencv.org/u/schorsch_76)\
**Post date:** [September 14, 2022, 3:19pm UTC](https://forum.opencv.org/t/videowriter-intelmfx-written-file-is-not-playable/10182/18 "2022-09-14T15:19:14Z")

</div>

It was (at least for me) a strange issue … without the look into the source it would have been much more difficult .