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• C++ - FFmpeg can't open hevc encoded *.mkv

  6 octobre 2020, par emdou

  I finally got the courage to tackle ffmpeg in C++ (and in general) for a stream extracting app but i'm stuck at loading the AVFormatContext using avformat_open_input, here is the actual code :

  


  int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    AVFormatContext *formatContext = nullptr;
    AVDictionaryEntry *dictEntry = nullptr;
    int result = 0;
    char filePath[] = "C:/Users/username/Downloads/test.mkv";

    if ((result = avformat_open_input(&formatContext, filePath, NULL, NULL)) < 0){
        av_log(NULL, AV_LOG_ERROR, "Cannot open file\n");
        result = AVERROR(result);
        goto cleanup;
    }

    while ((dictEntry = av_dict_get(formatContext->metadata, "", dictEntry, AV_DICT_IGNORE_SUFFIX))){
        qDebug() << dictEntry->key << " : " << dictEntry->value;
    }

cleanup:
    if (result < 0){
        char err[1024];
        av_strerror(result, err, 1024);
        qDebug() << err;
    }
    avformat_close_input(&formatContext);

    return a.exec();
}


  


  I end up with an error -12 as in "Cannot allocate memory" and exit code -1073741510.
This same sample is tested on an .mp4 file wich works just fine. What am I doing wrong ?

  


• Free and open-source lib to decode x.265 (HEVC) stream in a C project ?

  10 octobre 2020, par Ashkan Kh. Nazary

  I'm doing a project in C which requires playing an incoming stream of HEVC content to the user. My understanding is that I need a library that gives me an API to a HEVC decoder (not and encoder, but a decoder). Here are my options so far :

  


  

  • The x265 looks perfect but it's all about the encoding part (and nothing about decoding it !). I'm not interested in an API to a HEVC encoder, what I want is the decoder part.

  


  • There is libde265 and OpenHEVC but I'm not sure they have what I want. Couldn't find it anywhere in their docs that there is an API that I can use to decode the content but since there are players out there using those libs, I'm assuming it must be there somewhere ... couldn't find it though !

  


  • There is ffmpeg project with its own decoders (HEVC included) but I'm not sure this is the right thing since I only want the hevc decoder and nothing else.

  


  


  Cheers

  


• How can I open a rtsp stream with ffplay and feed the frames to opencv ?

  27 novembre 2020, par Scion11

  I'm working on a CV project streaming from an IP camera. I happened to find it is faster to stream with ffplay than with opencv directly. This is because opencv does not provide a flush()-like function that clears the buffer before retrieving a frame. In that case, opencv always takes the first frame instead of the last frame for use.

  


  I'm just wondering if there's a way to use ffplay (or ffmpeg) as backend to feed the latest frame to opencv.

  


  Comparing the following code, ffplay is much faster than opencv in streaming :

  


  import cv2
import subprocess


# OpenCV lags for ~1s
def cv2rtsp(rtspurl):
    cap = cv2.VideoCapture(rtspurl)
    ret, img = cap.read()

    while True:
        cap.grab()
        ret, img = cap.retrieve()
        if ret:
            cv2.imshow('video output', img)
        if cv2.waitKey(1) == ord('q'):
            raise StopIteration


# FFmpeg lags for ~500ms
def ffmpeg_rtsp(rtspurl):
    command = [
        'ffplay', '-fflags', 'nobuffer', '-flags', 'low_delay', '-framedrop', '-strict', 'experimental', rtspurl
    ]

    subprocess.call(command)


if __name__ == '__main__':
    rtsp = "rtsp://admin:my123456@192.168.0.53:554/h264/ch1/sub/av_stream"
    cv2rtsp(rtspurl=rtsp)
    ffmpeg_rtsp(rtspurl=rtsp)