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• Problem with processing FFMPEG video , the output video is totally black in first 3 seconds

  13 janvier 2021, par Trần Minh Tuấn

  I want to make a slideshow by using concat demuxer like this link :
https://trac.ffmpeg.org/wiki/Slideshow

  


  Here is the textfile preinputFiles.txt :

  


  file 'path a'
duration 2
file 'path b'
duration 2
file 'path c'
duration 2
file 'path c'


  


  and my command array is :

  


  String[] cmd = new String[]{
            "-f","concat","-i",
            textFile,
            "-vsync", "vfr", "-pix_fmt", "yuv420p",
            dest.getAbsolutePath()};


  


  the video has 3 seconds that it is totally black and run from 3s to 9s even the gallery shows that it is a 6 seconds long video .

  


  Thanks for the help !

  


• Create video file by mixing video and audio byte arrays FFmpeg & C++

  20 janvier 2021, par Sergey Zinovev

  I capture audio and video.

  


  Video is captured by using Desktop Duplication API and, as a result, I get Textures 2D.
These Textures 2D are char arrays.

  


  m_immediateContext->CopyResource(currTexture, m_acquiredDesktopImage.Get());&#xA;&#xA;D3D11_MAPPED_SUBRESOURCE* resource = new D3D11_MAPPED_SUBRESOURCE;&#xA;UINT subresource = D3D11CalcSubresource(0, 0, 0);&#xA;&#xA;m_immediateContext->Map(currTexture, subresource, D3D11_MAP_READ_WRITE, 0, resource);&#xA;&#xA;uchar * buffer = new uchar[(m_desc.Height * m_desc.Width * 4)];&#xA;const uchar * mappedData = static_cast<uchar>(resource->pData);&#xA;memcpy(buffer, mappedData, m_desc.Height * m_desc.Width * 4);&#xA;</uchar>

  


  Then the Textures 2D convert in cv::Mat and write Video using OpenCV.

  


  Audio captured by using WASAPI and, as a result, I get samples.

  


  BYTE * buffer = new BYTE[(numFramesAvailable * pwfx->nBlockAlign)];
memcpy(buffer, pData, numFramesAvailable * pwfx->nBlockAlign);


  


  These samples are byte arrays then write in WAV file.

  


  As a result, I get two files - video and audio, which merged by using FFmpeg.

  


  I want to skip the creation of video and audio files and promptly create one file compose of two strims (video and audio) from raw data.

  


  In order to make it I need help with FFmpeg code.
Specifically, in a way of creating and setting the correct output context and output streams, and how to encode raw data.

  


  I've already learned doc/examples FFmpeg, but still can't make the working code. So, I really need your help guys.

  


• video previews on video just like xvideos

  28 juin 2020, par zjose

  Video previews are usually images that rotate every so often in a small video. But since that format is old and boring, I would like to be able to create them with ffmpeg just like xvideos does.

  


  example (you don't have to worry) -> https://img-l3.xvideos-cdn.com/videos/videopreview/dc/8b/0f/dc8b0facd2879bad18f93dff44d1de2c_169.mp4

  


  They are in size : 362x204.
They last : 5 seconds.

  


  and they are several fragments in video, and not in images.

  


  How could I do it using ffmpeg ?