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• Get video from webcam using FFmpeg Libav

  27 mai 2022, par Hillel Rosensweig

  I am trying to record webcam video using FFmpeg C libraries (libav), on a Mac computer. I made changes to the transcode.c example so that it opens a device instead of a file. However, for some reason the code only receives a single packet and then closes.

  


  static int open_input_source(const char *dev_name) {
int ret;
unsigned int i;
AVDictionary *p_av_options = NULL;
AVInputFormat *p_av_input_format = av_find_input_format("avfoundation");
av_dict_set(&p_av_options, "framerate", "30", 0);

ifmt_ctx = NULL;
if ((ret = avformat_open_input(&ifmt_ctx, dev_name, p_av_input_format, &p_av_options) < 0)) {
    av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
    return ret;
}

if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {
    av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
    return ret;
}

stream_ctx = av_calloc(ifmt_ctx->nb_streams, sizeof(*stream_ctx));
if (!stream_ctx)
    return AVERROR(ENOMEM);

for (i = 0; i < ifmt_ctx->nb_streams; i++) {
    AVStream *stream = ifmt_ctx->streams[i];
    const AVCodec *dec = avcodec_find_decoder(stream->codecpar->codec_id);
    AVCodecContext *codec_ctx;
    if (!dec) {
        av_log(NULL, AV_LOG_ERROR, "Failed to find decoder for stream #%u\n", i);
        return AVERROR_DECODER_NOT_FOUND;
    }
    codec_ctx = avcodec_alloc_context3(dec);
    if (!codec_ctx) {
        av_log(NULL, AV_LOG_ERROR, "Failed to allocate the decoder context for stream #%u\n", i);
        return AVERROR(ENOMEM);
    }
    ret = avcodec_parameters_to_context(codec_ctx, stream->codecpar);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Failed to copy decoder parameters to input decoder context "
                                   "for stream #%u\n", i);
        return ret;
    }
    /* Reencode video & audio and remux subtitles etc. */
    if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
        || codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
        if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
            codec_ctx->framerate = av_guess_frame_rate(ifmt_ctx, stream, NULL);
        /* Open decoder */
        ret = avcodec_open2(codec_ctx, dec, NULL);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
            return ret;
        }
    }
    stream_ctx[i].dec_ctx = codec_ctx;

    stream_ctx[i].dec_frame = av_frame_alloc();
        if (!stream_ctx[i].dec_frame)
            return AVERROR(ENOMEM);
    }

    av_dump_format(ifmt_ctx, 0, dev_name, 0);
    return 0;
}


  


  I have looked for other code examples but they are all deprecated and no longer compile in updated FFmpeg.

  


  Is there some missing setting in my open_input_source function ? Alternatively, is the problem in using transcoding is my basis ? Should I try to use some other example ?

  


  In general, is there is a C source code reference which fulfills my requirements ?

  


  Thanks

  


• USB webcam streaming in ARM board (i.MX6)

  5 septembre 2017, par Titus

  I want to streaming the camera via NETWORK. I have connected the USB webcam to i.MX6 board and want to stream in Ubuntu14.04/16.04 via network.

  Incidentally, I have installed the gstreamer and ffmpeg tools for this in i.MX6 board.

  Also I am able to stream USB webcam within Ubuntu14.04 PC using the following ffmpeg commands. But it’s also not working if I use ffplay in other Ubuntu16.04 and I am not sure why (both are same ffmpeg versions).

  ffmpeg -f v4l2 -i /dev/video0 -preset ultrafast -vcodec libx264 -tune zerolatency -b 900k -f mpegts udp://192.168.0.37:1234
  
  
  
  ffplay udp://192.168.0.37:1234

  Ubuntu 16.06 : (NOT WORKING)

  tus@titus-PC:~/workdir$ ffplay udp://192.168.0.105:1234
  
  ffplay version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2003-2017 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  
    libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
      nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0  

  Ubuntu 14.04 : (WORKING)

  titus@titus-laptop:~$ 
  
  titus@titus-laptop:~$ ffplay udp://127.0.0.1:1234
  
  ffplay version 3.3.2 Copyright (c) 2003-2017 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
    configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libtheora --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab --enable-libwavpack --enable-nvenc
  
    libavutil      55. 58.100 / 55. 58.100
  
    libavcodec     57. 89.100 / 57. 89.100
  
    libavformat    57. 71.100 / 57. 71.100
  
    libavdevice    57.  6.100 / 57.  6.100
  
    libavfilter     6. 82.100 /  6. 82.100
  
    libavresample   3.  5.  0 /  3.  5.  0
  
    libswscale      4.  6.100 /  4.  6.100
  
    libswresample   2.  7.100 /  2.  7.100
  
    libpostproc    54.  5.100 / 54.  5.100
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced sq=    0B f=0/0   
  
      Last message repeated 1 times
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] no frame!
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced sq=    0B f=0/0   
  
  1751.47 M-V: -0.021 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0   
  
  1751.63 M-V: -0.020 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0   
  
  1751.80 M-V: -0.020 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0 

  Finally I want to stream with different ARM boards. Am also not able to build ffplay command. Same issue with raspberry pi too. I am doing something wrong or misunderstood something here ?

• avplay : Always free opts

  14 octobre 2014, par Luca Barbato

  avplay : Always free opts
  CC : libav-stable@libav.org
  
  Bug-Id : CID 733793
  

  • [DH] avplay.c