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• video preview from remote mp4 [h264] file

  20 novembre 2015, par sathia

  I was trying to make a video preview from a remote video (smaller size, short clip and no audio. you get the idea)

  By knowing the video duration, and bitrate (constant) is rather easy to make several byte-range requests in order to fetch chunks of it.

  Once all the needed chunks are downloaded I use the "concat" method of ffmpeg to make a single video (this is in order to avoid to download all the video locally)

  well, technically it all works perfectly the problem is that most of the chunks I download have pretty severe aberrations, and I mean, it’s usually all green and pixelated, rubbish.

  Is this a limit on the h264 protocol or I should maybe find the first keyframe and start from there (on each chunk of course) ? thanks

• How to extract audio tracks from a stream using FFMPEG or other tools ?

  17 septembre 2023, par Vassili Bagrov

  Here is the stream link that I am trying to download.

  


  I can download the video, but for some reason it doesn't include the audio stream.

  


  The audio stream is also in .ts format and has 1569 chunks.

  


  When I downloaded all the audio files, I tried to convert them in single temp.ts file to them convert it into an mp3 file with this command :

  


  cat audio_7e42e066-9f6c-44f4-9ac8-10b50c3edfae_*.ts > temp.ts


  


  I tried to then convert it into an mp3 file with this command :

  


  ffmpeg -i temp.ts -acodec copy out.mp3


  


  But got an error :

  


  temp.ts: Invalid data found when processing input


  


  What are my options to download audio files ? There are actually 3 audio tracks if I watch the video from the website.
Please tell me there is a way to do it other than screen record the whole video.

  


• VTK Requested modules not available vtkIOFFMPEG

  15 juillet 2019, par Anees Hikmat Abu Hmiad

  Im try to execute this example from VTK, and to do that I most install ffmpeg from this url and all is good, but when I try to build project I get this error :

  /Downloads/VTK-8.2.0/CMake/vtkModuleAPI.cmake:140 (message) :
  Requested modules not available :

  vtkIOFFMPEG

  I do all step in ffmpeg zipped file which I installed it from VTK download url, and if press ccmake on VTK-build directory I can see these option is enabled

  VTK_FFMPEG_INCLUDE_DIR /tmp/ffmpeg_inst/include
  VTK_FFMPEG_avcodec_LIBRARY /tmp/ffmpeg_inst/lib/libavcodec.so
  VTK_FFMPEG_avformat_LIBRARY /tmp/ffmpeg_inst/lib/libavformat.so
  VTK_FFMPEG_avutil_LIBRARY /tmp/ffmpeg_inst/lib/libavutil.so
  VTK_USE_FFMPEG_ENCODER ON

  and all files/directory is found and located under /tmp/ffmpeg_inst,
  Also I run make -j4 after VTK_USE_FFMPEG_ENCODER is set on.

  Why vtkIOFFMPEG module not found now ? is there any mistake in configuration or is there any specific configuration for FFMPEG example before build ? thanks.

  Additional Note :

  1. VTK version : 8.2.0
  2. cmake version 3.13.2