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• How to covert video and extract frame from video using FFMPEG in single command

  13 juillet 2013, par kheya

  I am trying to convert and extract image frame from a video file in single command
  I can do this in 2 steps but I want to use pipe like technique to do this

  This is what I have :
  for %%a in ("*.avi") do ffmpeg -i "%%a" -c:v libx264 -preset slow -crf 20 -c:a libvo_aacenc -b:a 128k "%%~na.mp4" <— converts correctly

  I need to incorporate this extract command :

  ffmpeg -i inputfile.avi  -r  1  -t  4  image-%d.jpeg

  Merging two commands giving error.

  How do I do it ?

  EDIT :
  This is what I have. But it just converts the video, no jpg image created as second output

  for %%a in ("*.avi") do ffmpeg -i "%%a" -c:v libx264 -preset slow -crf 20 -c:a libvo_aacenc -b:a 128k "%%~na.mp4" | ffmpeg -r 1 -s 4cif "%%~na.jpeg"

• ffmpeg encoding a video with time_base Not equal to framerate does not work in HML5 video players

  1er juillet 2019, par Gilgamesh22

  I have a time_base of 90000 with a frame rate of 30. I can generate a h264 video and have it work in VLC but this video does not work in the browser player. If I change the time_base to 30 It works fine.

  Note : I am changing the frame->pts appropriately to match the time_base.
  Note : Video does not have audio stream

  //header.h
  
  AVCodecContext *cctx;
  
  AVStream* stream;

  Here is the non working example code

  //source.cpp
  
  stream->time_base = { 1, 90000 };
  
  stream->r_frame_rate = { fps, 1 };
  
  stream->avg_frame_rate = { fps, 1 };
  
  
  
  cctx->codec_id = codecId;
  
  cctx->time_base = { 1 ,  90000 };
  
  cctx->framerate = { fps, 1 };
  
  
  
  // ...... 
  
  // add frame code later on timestamp are in millisecond
  
  frame->pts = (timestamp - startTimeStamp)* 90;

  Here is the working example code

  //source.cpp
  
  stream->time_base = { 1, fps};
  
  stream->r_frame_rate = { fps, 1 };
  
  stream->avg_frame_rate = { fps, 1 };
  
  
  
  cctx->codec_id = codecId;
  
  cctx->time_base = { 1 ,  fps};
  
  cctx->framerate = { fps, 1 };
  
  
  
  // ...... 
  
  //  add frame code timestamp are in millisecond
  
  frame->pts = (timestamp - startTimeStamp)/(1000/fps);

  Any ideas on why the second example works and the first does not in the HTML5 video player.

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

  20 janvier 2021, par Sergey Zinovev

  I capture audio and video.

  &#xA;

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

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  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>

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

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

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


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  These samples are byte arrays then write in WAV file.

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

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  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.

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

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

  &#xA;