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• Trying to concat videos from different sources with ffmpeg and get different broken results every time (partly no audio and/or fast forward video)

  30 octobre 2022, par Oliver

  I am using ffmpeg for years to create (merge and render) big video files from the (vaction) clips my sony camcorder produces. My basic workflow is to copy the mp4 files from the camcorder over to my pc, put the names in a file (file 'filename') and use the following command to create one big file that is playable by my apple tv :

  


  ffmpeg -f concat -safe 0 -i filelist.txt -c:v libx265 -preset slow -x265-params strong-intra-smoothing=0:merange=58 -crf 24 -c:a aac -b:a 320k -tag:v hvc1 output.mp4


  


  i cannot explain most of the arguments in total detail but i know that it works.
My problem occurred as i wanted to prepend some video clips recorded with an iphone to one of those files. So the first part seemed easy, the sony camcorder files have a resolution of 3840x2160 and the iphone video clips have a resolution of 1280x720 so at first i upscaled the iphone files using this command (i would have rather done in just one step but i do not know how to do that) :

  


  ffmpeg -i IMG_1182.MP4 -vf scale=3840:2160 IMG_1182_3840x2160.MP4


  


  then i just tried to add those upscaled video files to the filelist from the first command and ran the command for all clips again. Sadly that did not worked, as the resulting file contained all clips but only the iphone part had audio ! For the rest of the video the audio was missing. At this point i also did not noticed that the second part was played much faster (like played in fast forward mode). So guessed that i have to render the iphone and sony camcorder clips separately using the first command. That worked and i got two video files with perfect audio and video. My next step was to concatenate the resulting files using the following simple command :

  


  ffmpeg -f concat -safe 0 -i concatlist.txt -c copy output.mp4


  


  where concatlist contained both files.
Sadly that also did not worked. I do got a file containing both parts, this time with audio, but the video of the second part still was fast forward !

  


  I do not know what to do at this point, and i also do not understand enough to experiment with the options any more. Can someone explain to my what could be the problems here and how to solve them ?

  


• Encoding SWF to video with Melt

  17 août 2015, par RocketR

  I’m doing a project which requires converting SWF movies to H.264 video on server-side, to be able to play them both in Flash player and on iPhone/iPad. And I really got stuck.

  I’m using Melt from http://www.mltframework.org/ and this is my command-line :

  melt movie.swf -consumer avformat:video.mp4 r=30 s=640x360 f=mp4 acodec=aac ab=128k ar=48000 vcodec=libx264 b=1000k an=1

  It does play in Flash player, but fails to play on iDevices. I googled for iPhone video requirements and it seems my video files do satisfy them(frame size, framerate and bitrate). What settings should I change to make it play ?

• OpenGL ES glReadPixels exc_bad_access

  6 décembre 2011, par Yanny

  I'm trying to create video from images using OpenGL ES and ffmpeg, but on iPad(4.3) I have a crash on glReadPixels

  -(NSData *) glToUIImage {
  
  
  
      int numberOfComponents = NUMBER_OF_COMPONENTS; //4
  
      int width = PICTURE_WIDTH; 
  
      int height = PICTURE_HEIGHT;
  
  
  
      NSInteger myDataLength = width * height * numberOfComponents;   
  
  
  
      NSMutableData * buffer= [NSMutableData dataWithLength :myDataLength];    
  
  
  
      [self checkForGLError]; 
  
  
  
      GLenum type = NUMBER_OF_COMPONENTS == 3 ? GL_RGB : GL_RGBA; //RGBA
  
      glReadPixels(0, 0, width, height, type, GL_UNSIGNED_BYTE, [buffer mutableBytes]);   //EXC_BAD_ACCESS here
  
  
  
      return buffer; 
  
  }

  It is working on iPhone 4 (4.3) and iPod Touch, but have problems on iPhone 3G(3.0) and iPad(4.3). Can you help me with this issue ?

  Also on iPhone 3G(3.0) and iPad(4.3) I have problems with Video - first 5-20 video frames have trash. Maybe issue with optimization ? Or architecture ?

  EDITED
  Stack :

  #0  0x33be3964 in void BlockNxN<64ul, 16ul, 1, BLOCK_CONVERTER_NULL_32>(unsigned long, int, int, unsigned long, int, int, unsigned int, unsigned int, unsigned int, unsigned int) ()
  
  #1  0x33be1c76 in glrBIFDetile ()
  
  #2  0x33b586b2 in sgxGetImage(SGXImageReadParams const*) ()
  
  #3  0x33b50d38 in gldReadPixels ()
  
  #4  0x31813e16 in glReadPixels_Exec ()
  
  #5  0x31e3c518 in glReadPixels ()