Newest 'libx264' Questions - Stack Overflow

Articles published on the website

  • FFMPEG (libx264) "height not divisible by 2"

    27 January, by Andy Hin

    I am trying to encode a .mp4 video from a set of frames using FFMPEG using the libx264 codec.

    This is the command I am running:

    /usr/local/bin/ffmpeg -r 24 -i frame_%05d.jpg -vcodec libx264 -y -an video.mp4

    I sometimes get the following error:

    [libx264 @ 0xa3b85a0] height not divisible by 2 (520x369)

    After searching around a bit it seems that the issue has something to do with the scaling algorithm and can be fixed by adding a -vf argument.

    However, in my case I don't want to do any scaling. Ideally, I want to keep the dimensions exactly the same as the frames. Any advice? Is there some sort of aspect ratio that h264 enforces?

  • libx264 codec not enabled in ffmpeg ubuntu 18.04

    18 January, by Bendemann

    I have some weird codec installation issues with the following docker image.

    ARG PYTORCH="1.8.0"
    ARG CUDA="11.1"
    ARG CUDNN="8"
    FROM pytorch/pytorch:${PYTORCH}-cuda${CUDA}-cudnn${CUDNN}-devel
    ENV TORCH_CUDA_ARCH_LIST="6.0 6.1 7.0 8.0+PTX"
    ENV TORCH_NVCC_FLAGS="-Xfatbin -compress-all"
    ENV CMAKE_PREFIX_PATH="$(dirname $(which conda))/../"
    RUN apt-key del 7fa2af80
    RUN apt-key adv --fetch-keys
    RUN apt-key adv --fetch-keys
    RUN apt-get update && apt-get install -y \
            git nano ninja-build p7zip-full imagemagick wget unzip \
            libglib2.0-0 libsm6 libxrender-dev libxext6 libturbojpeg \
            libxrender1 libfontconfig1 freeglut3-dev llvm-6.0-tools curl \
            amqp-tools ffmpeg libx264-dev \
        && apt --fix-broken install \
        && apt-get clean \
        && rm -rf /var/lib/apt/lists/* \
        # for visualizing
        && wget \
        && dpkg -i ./mesa_18.3.3-0.deb || true \
        && apt install -f \
        && git clone \
        && pip install ./pyopengl

    First of all, libx264 is supposed to be installed by a simple apt-get install ffmpeg in ubuntu 18.04.5. Indeed I see that it is being installed in the installation instructions but for some reason, it's not enabled. This is confirmed when running ffmpeg -codecs | grep 264, which doesn't show libx264 (only h264, libopenh264 are there).

    In addition, I also compiled from source, explicitly enabling libx264 during installation. It didn't make a difference.

  • Lib x: display problem related to window pixel color changes with the mlx_put_pixel() function [closed]

    15 January, by Jordan Riga

    I'm stuck on a project that I have to return for school. I have to make a 3D game with the minilibx in C, the problem being that I try to make the graphic part work but it doesn't work (display pixels on the screen). And all this same with the examples that I found of school 42 on the internet in that link All configuration has been done.

    Could there be a possible configuration problem? I'm working on Kali Linux (Even using a VM on Ubuntu it didn't work).

    In short my question is what can be the different reasons why the graphical part of minilibx independently of events, loops and etc does not work without errors ?

  • OpenCV VideoWriter using ffmpeg with "Could not open codec 'libx264'" Error

    17 December 2022, by user2262504

    I am new to OpenCV, and I want write Mat images into video using VideoWriter on Ubuntu 12.04. But when constructing VideoWriter, errors came out.

    It seems that OpenCV invoke ffmpeg API using default parameters and ffmpeg invoke x264 using its default parameters. Then these setting is broken for libx264. Thus the "Could not open codec 'libx264'" error.

    Anyone has ideas to solve this problem?

    More specifically:

    1. anyone knows where and how OpenCV invoke ffmpeg API?
    2. how to change ffmpeg default settings using code, hopefull, can be easily embeded into OpenCV?
    3. will changes of default in ffmpeg be carried to libx264?


    1. Uising CV_FOURCC('H', '2', '6', '4')
    [libx264 @ 0x255de40] broken ffmpeg default settings detected
    [libx264 @ 0x255de40] use an encoding preset (e.g. -vpre medium)
    [libx264 @ 0x255de40] preset usage: -vpre  -vpre 
    [libx264 @ 0x255de40] speed presets are listed in x264 --help
    [libx264 @ 0x255de40] profile is optional; x264 defaults to high
    Could not open codec 'libx264': Unspecified error
    2. Using FOURCC = -1 to invoke user customized codec
    OpenCV Error: Unsupported format or combination of formats (Gstreamer Opencv 
    backend doesn't support this codec acutally.) in CvVideoWriter_GStreamer::open, 
    file /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp, 
    line 505 terminate called after throwing an instance of 'cv::Exception'
    what():  /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp:
    505: error: (-210) Gstreamer Opencv backend doesn't support this codec acutally.
    in function CvVideoWriter_GStreamer::open


    int main(int argc, char *argv[])
        VideoWriter outputVideo;
        bool fourcc_on = true; //switch on / off different error
        if (fourcc_on)
  "outVideo.avi", CV_FOURCC('H', '2', '6', '4'), 25, Size(100, 100), true);
  "outVideo.avi", -1, 25, Size(100, 100), true);
        if (!outputVideo.isOpened())
            cout  << "Could not open the output video for write" << endl;
            return -1;
        return 0;

    OpenCV Configuration:

    -- Detected version of GNU GCC: 46 (406)
    -- Found OpenEXR: /usr/lib/
    -- Looking for linux/videodev.h
    -- Looking for linux/videodev.h - not found
    -- Looking for linux/videodev2.h
    -- Looking for linux/videodev2.h - found
    -- Looking for sys/videoio.h
    -- Looking for sys/videoio.h - not found
    -- Looking for libavformat/avformat.h
    -- Looking for libavformat/avformat.h - found
    -- Looking for ffmpeg/avformat.h
    -- Looking for ffmpeg/avformat.h - not found
    -- General configuration for OpenCV 2.4.8 =====================================
    --   Version control:               unknown
    --   Platform:
    --     Host:                        Linux 3.8.0-38-generic x86_64
    --     CMake:                       2.8.7
    --     CMake generator:             Unix Makefiles
    --     CMake build tool:            /usr/bin/make
    --     Configuration:               RELEASE
    --   C/C++:
    --     Built as dynamic libs?:      YES
    --     C++ Compiler:                /usr/bin/c++  (ver 4.6)
    --     C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
    --     C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
    --     C Compiler:                  /usr/bin/gcc
    --     C flags (Release):           -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 -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
    --     C flags (Debug):             -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 -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
    --     Linker flags (Release):      
    --     Linker flags (Debug):        
    --     Precompiled headers:         YES
    --   OpenCV modules:
    --     To be built:                 core flann imgproc highgui features2d calib3d ml video legacy objdetect photo gpu ocl nonfree contrib python stitching superres ts videostab
    --     Disabled:                    world
    --     Disabled by dependency:      -
    --     Unavailable:                 androidcamera dynamicuda java
    --   GUI: 
    --     QT:                          NO
    --     GTK+ 2.x:                    YES (ver 2.24.10)
    --     GThread :                    YES (ver 2.32.4)
    --     GtkGlExt:                    NO
    --     OpenGL support:              NO
    --   Media I/O: 
    --     ZLib:                        /usr/lib/x86_64-linux-gnu/ (ver
    --     JPEG:                        /usr/lib/x86_64-linux-gnu/ (ver )
    --     PNG:                         /usr/lib/x86_64-linux-gnu/ (ver 1.2.46)
    --     TIFF:                        /usr/lib/x86_64-linux-gnu/ (ver 42 - 3.9.5)
    --     JPEG 2000:                   /usr/lib/x86_64-linux-gnu/ (ver 1.900.1)
    --     OpenEXR:                     /usr/lib/ /usr/lib/ /usr/lib/ /usr/lib/ /usr/lib/ (ver 1.6.1)
    --   Video I/O:
    --     DC1394 1.x:                  NO
    --     DC1394 2.x:                  YES (ver 2.2.0)
    --     FFMPEG:                      YES
    --       codec:                     YES (ver 55.58.105)
    --       format:                    YES (ver 55.37.101)
    --       util:                      YES (ver 52.78.100)
    --       swscale:                   YES (ver 2.6.100)
    --       gentoo-style:              YES
    --     GStreamer:                   
    --       base:                      YES (ver 0.10.36)
    --       app:                       YES (ver 0.10.36)
    --       video:                     YES (ver 0.10.36)
    --     OpenNI:                      NO
    --     OpenNI PrimeSensor Modules:  NO
    --     PvAPI:                       NO
    --     GigEVisionSDK:               NO
    --     UniCap:                      NO
    --     UniCap ucil:                 NO
    --     V4L/V4L2:                    Using libv4l (ver 1.0.1)
    --     XIMEA:                       NO
    --     Xine:                        NO
    --   Other third-party libraries:
    --     Use IPP:                     NO
    --     Use Eigen:                   NO
    --     Use TBB:                     NO
    --     Use OpenMP:                  NO
    --     Use GCD                      NO
    --     Use Concurrency              NO
    --     Use C=:                      NO
    --     Use Cuda:                    NO
    --     Use OpenCL:                  YES
    --   OpenCL:
    --     Version:                     dynamic
    --     Include path:                /home/shixudongleo/Downloads/opencv-2.4.8/3rdparty/include/opencl/1.2
    --     Use AMD FFT:                 NO
    --     Use AMD BLAS:                NO
    --   Python:
    --     Interpreter:                 /usr/bin/python (ver 2.7.3)
    --     Libraries:                   /usr/lib/
    --     numpy:                       /usr/lib/python2.7/dist-packages/numpy/core/include (ver 1.6.1)
    --     packages path:               lib/python2.7/dist-packages
    --   Java:
    --     ant:                         NO
    --     JNI:                         NO
    --     Java tests:                  NO
    --   Documentation:
    --     Build Documentation:         NO
    --     Sphinx:                      NO
    --     PdfLaTeX compiler:           /usr/bin/pdflatex
    --   Tests and samples:
    --     Tests:                       YES
    --     Performance tests:           YES
    --     C/C++ Examples:              NO
    --   Install path:                  /usr/local
    --   cvconfig.h is in:              /home/shixudongleo/Downloads/opencv-2.4.8/build
    -- -----------------------------------------------------------------
    -- Configuring done
    -- Generating done
    -- Build files have been written to: /home/XXX/Downloads/opencv-2.4.8/build


    ffmpeg is enable to support OpenCV and libx264 is enabled when compiling ffmpeg. By using ffmpeg command line, libx264 is running normally.

    $ ffmpeg -i test.avi -vcodec libx264 test.mp4
    ffmpeg -i test.avi -vcodec libx264 test.mp4 > ~/Downloads/ffmpeg_log.txt
    ffmpeg version 2.2.git Copyright (c) 2000-2014 the FFmpeg developers
      built on Apr 24 2014 16:39:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
      configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-shared --enable-pic
      libavutil      52. 78.100 / 52. 78.100
      libavcodec     55. 58.105 / 55. 58.105
      libavformat    55. 37.101 / 55. 37.101
      libavdevice    55. 13.100 / 55. 13.100
      libavfilter     4.  4.100 /  4.  4.100
      libswscale      2.  6.100 /  2.  6.100
      libswresample   0. 18.100 /  0. 18.100
      libpostproc    52.  3.100 / 52.  3.100
    Input #0, avi, from 'test.avi':
      Duration: 00:00:03.73, start: 0.000000, bitrate: 1757 kb/s
        Stream #0:0: Video: msvideo1 (CRAM / 0x4D415243), rgb555le, 320x240, 1781 kb/s, 15 tbr, 15 tbn, 15 tbc
          title           : julius.avi Video #1
    File 'test.mp4' already exists. Overwrite ? [y/N] y
    No pixel format specified, yuv444p for H.264 encoding chosen.
    Use -pix_fmt yuv420p for compatibility with outdated media players.
    [libx264 @ 0x25d08e0] using cpu capabilities: none!
    [libx264 @ 0x25d08e0] profile High 4:4:4 Predictive, level 1.2, 4:4:4 8-bit
    [libx264 @ 0x25d08e0] 264 - core 142 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
    Output #0, mp4, to 'test.mp4':
        encoder         : Lavf55.37.101
        Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 320x240, q=-1--1, 15360 tbn, 15 tbc
          title           : julius.avi Video #1
    Stream mapping:
      Stream #0:0 -> #0:0 (msvideo1 -> libx264)
    Press [q] to stop, [?] for help
    frame=   56 fps=0.0 q=-1.0 Lsize=     321kB time=00:00:03.60 bitrate= 731.0kbits/s    
    video:320kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.409949%
    [libx264 @ 0x25d08e0] frame I:3     Avg QP:15.36  size:  7975
    [libx264 @ 0x25d08e0] frame P:38    Avg QP:26.05  size:  6230
    [libx264 @ 0x25d08e0] frame B:15    Avg QP:28.25  size:  4418
    [libx264 @ 0x25d08e0] consecutive B-frames: 46.4% 53.6%  0.0%  0.0%
    [libx264 @ 0x25d08e0] mb I  I16..4:  1.4% 72.8% 25.8%
    [libx264 @ 0x25d08e0] mb P  I16..4:  1.6%  5.7% 15.1%  P16..4:  7.6%  6.3%  7.4%  0.0%  0.0%    skip:56.3%
    [libx264 @ 0x25d08e0] mb B  I16..4:  0.2%  1.0%  2.0%  B16..8: 13.3%  7.8%  8.7%  direct: 8.3%  skip:58.8%  L0:34.9% L1:36.6% BI:28.5%
    [libx264 @ 0x25d08e0] 8x8 transform intra:37.7% inter:2.3%
    [libx264 @ 0x25d08e0] coded y,u,v intra: 52.1% 42.1% 30.1% inter: 19.6% 9.2% 5.2%
    [libx264 @ 0x25d08e0] i16 v,h,dc,p: 56% 17% 24%  2%
    [libx264 @ 0x25d08e0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 16% 68%  1%  1%  1%  1%  1%  1%
    [libx264 @ 0x25d08e0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 18% 28%  5%  6%  5%  7%  5%  6%
    [libx264 @ 0x25d08e0] Weighted P-Frames: Y:31.6% UV:21.1%
    [libx264 @ 0x25d08e0] ref P L0: 70.5%  9.0% 12.1%  6.5%  2.0%
    [libx264 @ 0x25d08e0] ref B L0: 91.3%  8.7%
    [libx264 @ 0x25d08e0] kb/s:700.56
  • very low latency streaminig with ffmpeg using a webcam

    10 December 2022, by userDtrm

    I'm trying to configure ffmpeg to do a real-time video streaming using a webcam. The ffmpeg encoder command I use is as follows.

    ffmpeg -f v4l2 -input_format yuyv422 -s 640x480 -i /dev/video0 -c:v libx264 -profile:v baseline -trellis 0 -subq 1 -level 32 -preset superfast -tune zerolatency -me_method epzs -crf 30 -threads 0 -bufsize 1 -refs 4 -coder 0 -b_strategy 0 -bf 0 -sc_threshold 0 -x264-params vbv-maxrate=2000:slice-max-size=1500:keyint=30:min-keyint=10: -pix_fmt yuv420p -an -f mpegts udp://

    The ffplay command used to display the video feed is,

    ffplay -analyzeduration 1 -fflags -nobuffer -i udp://

    However, I'm experiencing a latency of 0.5 - 1.0s latency in the video stream. Is there a way to reduce this to a number less than 100ms. Also, when I replace the v4l2 camera capture with a screen capture using x11grab, the stream is almost real-time and I experience no noticeable delays. Moreover, changing the encoder from x264 to mpeg2 had no effect on the latency. In addition, the statistics from the ffmpeg shows that the encoder is performing at a 30fps rate, which I believe indicates that the encoding is real-time. This leaves me with only one reason for the experienced delay.

    • Is there a significant delay in buffers when using v4l2 during video capturing in a webcam?
    • I don't think the transmission delay is in effect in this case as I see no latencies when screen capture is used under the same conditions.
    • Can this latency be further reduced?. Can someone think of a different encoder configuration to be used instead of the one that I've been using?