Videowriter not working properly when deployed on Heroku

I am trying to write a video using the command cv2.VideoWriter() but when I deploy my app on heroku, I am not able to use most of the video codecs such h264, mp4v, and even if I use webm codec (vp80) I get this error [matroska,webm @ 0x556363aef780] File ended prematurely which causes the video to end abruptly along with the warning `OpenCV: FFMPEG: tag 0x30387076/‘vp80’ is not supported with codec id 139 and format ‘webm / WebM’

I have added the following libraries -


and the following buildpack for heroku - GitHub - jonathanong/heroku-buildpack-ffmpeg-latest: A Heroku buildpack for ffmpeg that always downloads the latest static build

please guide me on what video codecs to use or if I am missing anything specific.


you can’t just install a python package called “ffmpeg” and hope that works. that’ll certainly not work because that package is some random person’s horrible wrapper around ffmpeg. OpenCV doesn’t use that.

Thanks for the prompt reply. I ran the code snippet you mentioned and this is what I am getting. I can see ffmpeg installed but not sure if its exactly what needs to be installed. Please let me know if anything is wrong here.

General configuration for OpenCV 4.5.2 =====================================
  Version control:               4.5.2-dirty

  Extra modules:
    Location (extra):            /tmp/pip-req-build-sl2aelck/opencv_contrib/modules
    Version control (extra):     4.5.2

    Timestamp:                   2021-06-07T09:11:43Z
    Host:                        Linux 5.4.0-1047-azure x86_64
    CMake:                       3.20.2
    CMake generator:             Unix Makefiles
    CMake build tool:            /bin/gmake
    Configuration:               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 (15 files):         + SSSE3 SSE4_1
      SSE4_2 (1 files):          + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (0 files):            + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (4 files):             + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (29 files):           + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (4 files):      + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX

    Built as dynamic libs?:      NO
    C++ standard:                11
    C++ Compiler:                /usr/lib/ccache/compilers/c++  (ver 9.3.1)
    C++ flags (Release):         -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /usr/lib/ccache/compilers/cc
    C flags (Release):           -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed  
    Linker flags (Debug):        -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed  
    ccache:                      YES
    Precompiled headers:         NO
    Extra dependencies:          Qt5::Test Qt5::Concurrent /lib64/ /lib64/ Qt5::Core Qt5::Gui Qt5::Widgets dl m pthread rt
    3rdparty dependencies:       ittnotify libprotobuf ade libjpeg-turbo libwebp libtiff libopenjp2 IlmImf quirc ippiw ippicv

  OpenCV modules:
    To be built:                 aruco bgsegm bioinspired calib3d ccalib core cvv datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 alphamat cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev freetype hdf java julia matlab ovis python2 sfm ts viz
    Applications:                -
    Documentation:               NO
    Non-free algorithms:         NO

    QT:                          YES (ver 5.15.0)
      QT OpenGL support:         NO
    GTK+:                        NO
    VTK support:                 NO

  Media I/O: 
    ZLib:                        /lib64/ (ver 1.2.7)
    JPEG:                        libjpeg-turbo (ver 2.0.6-62)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /lib64/ (ver 1.5.13)
    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
      avcodec:                   YES (58.109.100)
      avformat:                  YES (58.61.100)
      avutil:                    YES (56.60.100)
      swscale:                   YES (5.8.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Intel IPP:                   2020.0.0 Gold [2020.0.0]
           at:                   /tmp/pip-req-build-sl2aelck/_skbuild/linux-x86_64-3.8/cmake-build/3rdparty/ippicv/ippicv_lnx/icv
    Intel IPP IW:                sources (2020.0.0)
              at:                /tmp/pip-req-build-sl2aelck/_skbuild/linux-x86_64-3.8/cmake-build/3rdparty/ippicv/ippicv_lnx/iw
    VA:                          NO
    Lapack:                      NO
    Eigen:                       NO
    Custom HAL:                  NO
    Protobuf:                    build (3.5.1)

  OpenCL:                        YES (no extra features)
    Include path:                /tmp/pip-req-build-sl2aelck/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 3:
    Interpreter:                 /opt/python/cp38-cp38/bin/python (ver 3.8.6)
    Libraries:                   libpython3.8.a (ver 3.8.6)
    numpy:                       /tmp/pip-build-env-sef97t8m/overlay/lib/python3.8/site-packages/numpy/core/include (ver 1.17.3)
    install path:                python

  Python (for build):            /bin/python2.7

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

  Install to:                    /tmp/pip-req-build-sl2aelck/_skbuild/linux-x86_64-3.8/cmake-install

good, ffmpeg is present and I see no strange versions.

okay, now share the minimal reproducible example for the issue, and the data (video file) that you are trying to read/write (if it outputs anything at all, it’d be helpful to see that file)

My code snippet :-

cap = cv2.VideoCapture(f'/tmp/{filenm}')
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 320)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
ret, frame =
fps = cap.get(cv2.CAP_PROP_FPS)
frame_width = int(cap.get(3))
frame_height = int(cap.get(4))
out = cv2.VideoWriter(f'/tmp/final{filenm}.webm',cv2.VideoWriter_fourcc(*'vp80'), fps, (frame_width,frame_height))
                            (50, 50), 
                            font, 1, 
                            (0, 128, 0), 
                            (50, 100), 
                            font, 1, 
                            (0, 128, 0), 

totals[i] contains some pre-calculated integers.

Here are the input and output files:-

the output video has 3 to 4 seconds less than the original video in the end, and also it’s not complete hence you cannot toggle the controls.

you forgot to call out.release() at the end

always follow official documentation, not some questionable video tutorials on youtube made by someone who doesn’t know OpenCV.