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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

  


• fate/filter-video : Avoid duplication for fate-filter-stereo3d tests

  16 mai 2022, par Andreas Rheinhardt

  fate/filter-video : Avoid duplication for fate-filter-stereo3d tests
  Also fix the requirements of these tests : Only the anaglyph
  
  tests need a scale filter, yet it has been inserted for all tests
  
  without any check for its presence.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] tests/fate/filter-video.mak

• fate/filter-video : Avoid duplication for fate-filter-overlay tests

  17 mai 2022, par Andreas Rheinhardt

  fate/filter-video : Avoid duplication for fate-filter-overlay tests
  Also add a fate-filter-overlays target containing all these tests
  
  and fix the requirements of the tests ; furthermore, remove
  
  unnecessary scale filters from filter-overlay-rgba ?_rgba.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] tests/fate/filter-video.mak