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• I want to separate MPEG2ts data into images and metadata (klv)

  4 août 2020, par 夏目たかし

  please. Help me.
  
I would like to separate the streamed MPEG2ts data into images and metadata (klv).
  

  


  Delivery
  
ffmpeg -fflags +genpts -re -i NightFlightIR.mpg -f mpegts -c copy -map 0:v -map 0:d udp ://127.0.0.1:5004
  

  
reception
  
ffmpeg -i 'udp ://127.0.0.1:5004' -vsync 0 -q:v 2 -f image2 -update 1 img.jpg -c copy -map d:0 -f data klv.bin
  

  
The image is output, but the klv.bin is empty.
  

  
This command outputs data to standard output, but cannot output to a file.
  
ffmpeg -i 'udp ://127.0.0.1:5004' -vsync 0 -q:v 2 -f image2 -update 1 img.jpg -c copy -map d:0 -f data -
  

  
On ffmpeg2.8.6, the klv.bin contains data, but on 3.x and 4.x, it's empty.
  
Is it possible to write klv data to klv.bin on 4.x ?
  

  


• QAudioSink play AVFrame data decoded by ffmpeg

  26 mai 2022, par liuyulvv

  I want to using QAudioSink to play PCM data decoded by ffmpeg.

  


  I first try to play a pcm file and I made it :

  


  Here is the override function readData of QIODevice

  


  qint64 PCMDevice::readData(char *data, qint64 maxlen)
{
    int len = m_inputFile.size();
    len = len < maxlen ? len : maxlen;

    m_inputFile.read(data, len);
    return len;
}


  


  And I get the right result, the file is playing.

  


  But I want to play AVFrame data from the memory :

  


  qint64 PCMDevice::readData(char *data, qint64 maxlen)
{
    AVFrame *res = getFrame();
    if (res == nullptr)
        return 0;

    // Something wrong here
    auto ret = res->nb_samples;
    memcpy(data, res->data[0], ret);

    delete res;
    res = nullptr;
    return ret;
}


  


  How to make AVFrame's data to the data that QAudioSink need ?

  


  I'm pretty sure I'm using the correct sample_fmt, sample_rate etc.

  


  Where is the data of the stereo AVFrame and how to copy it to the data correctly ?

  


• Is raw audio in AVFrame->data the same as LPCM ?

  4 décembre 2023, par CheekyChips

  In the ffmpeg documentation for an AVFrame it says

  


  


  This structure describes decoded (raw) audio or video data.

  


  


  In the case of audio data, what format are the samples within an AVFrame in ? Do they basically look like raw LPCM samples ? If you decode audio data into an AVFrame (i.e. via avcodec_send_packet() ... avcodec_receive_frame()) does the audio data of the packet look the same, regardless of what encoding it was originally in in the packet (assuming the same sample rate, sample format, etc) ?

  


  Based on the question How is decoded audio data stored in ffmpeg AVFrame ? it seems like this is the case, but I want to know if this is the same as LPCM, regardless of what encoding the audio data was in before ?

  


  Bonus question : If it is the same as LPCM, why would you use a PCM encoder (e.g. ""pcm_f32le") to encode the frame data to AVPackets ? Does the internal data look the same ? Is it just in order to use functions that take AVPackets like av_interleaved_write_frame()