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• vframes option ignored in ffmpeg ?

  25 mars 2016, par cooper

  I have a directory that contains 2001 PNG files. I can convert all of the frames to an mp4 video using ffmpeg and the following command :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -c:v libx264 -r 30 \
  
  -pix_fmt yuv420p input1ia.mp4

  This works fine. However, I am creating a more complicated application that needs to read only the first 1020 files in the directory (specifically 0 thru 1019). Some googling around led me to the -vframes option. My problem is — it seems to get ignored or at least interpreted differently than I expect.

  My modified command looks like :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -vframes 1020 -c:v libx264 
  
  -r 30 -pix_fmt yuv420p input1.mp4

  It seems like many other people doing the same thing as me do not encounter this issue. So I did some more digging. I tried changing vframes from 1020 to -vframes 20, and this seemed to work properly. So now I am thinking it might be some kind of mismatch between -framerate and -r ?

  The full resultant video is 33 sec long... which makes sense mathematically.

   1 sec
  
   ---------   x  2001 frames = 33.35 seconds
  
   60 frames

  That’s why I thought that specifying 1/2 of the PNGs as the ’end point’ would result in a video of the first 16-17 seconds. But I always get the full length video from using the -vframes option.

  I assume my input to -vframes must be incorrect mathematically, since a small number of frames seems to work. However, I do not understand why.

  The most educated guess I can seem to make is that it is reading the PNGs as 60fps (-framerate), but the -r makes the output video 30fps or something ? However, then I would assume that the full output video would not be 33 seconds long.

• vframes option ignored in ffmpeg ?

  25 mars 2016, par cooper

  I have a directory that contains 2001 PNG files. I can convert all of the frames to an mp4 video using ffmpeg and the following command :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -c:v libx264 -r 30 \
  
  -pix_fmt yuv420p input1ia.mp4

  This works fine. However, I am creating a more complicated application that needs to read only the first 1020 files in the directory (specifically 0 thru 1019). Some googling around led me to the -vframes option. My problem is — it seems to get ignored or at least interpreted differently than I expect.

  My modified command looks like :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -vframes 1020 -c:v libx264 
  
  -r 30 -pix_fmt yuv420p input1.mp4

  It seems like many other people doing the same thing as me do not encounter this issue. So I did some more digging. I tried changing vframes from 1020 to -vframes 20, and this seemed to work properly. So now I am thinking it might be some kind of mismatch between -framerate and -r ?

  The full resultant video is 33 sec long... which makes sense mathematically.

   1 sec
  
   ---------   x  2001 frames = 33.35 seconds
  
   60 frames

  That’s why I thought that specifying 1/2 of the PNGs as the ’end point’ would result in a video of the first 16-17 seconds. But I always get the full length video from using the -vframes option.

  I assume my input to -vframes must be incorrect mathematically, since a small number of frames seems to work. However, I do not understand why.

  The most educated guess I can seem to make is that it is reading the PNGs as 60fps (-framerate), but the -r makes the output video 30fps or something ? However, then I would assume that the full output video would not be 33 seconds long.

• Metadata is not showing ffmpeg C++

  18 août 2015, par Kaidul Islam

  I am muxing h264 encoded video data and PCM g711 encoded audio data into a .mov media container. I am trying to write metadata on header but the metadata is not showing when I go to file->right click->properties->details on windows and likewise in Ubuntu. This is my code -

  // Instead of creating new AVDictionary object, I also tried following way
  
  // stated here: http://stackoverflow.com/questions/17024192/how-to-set-header-metadata-to-encoded-video 
  
  // but no luck
  
  AVDictionary* pMetaData = m_pFormatCtx->metadata;
  
  av_dict_set(&pMetaData, "title", "Cloud Recording", 0);
  
  av_dict_set(&pMetaData, "artist", "Foobar", 0);
  
  av_dict_set(&pMetaData, "copyright", "Foobar", 0);
  
  av_dict_set(&pMetaData, "filename", m_sFilename.c_str(), 0);
  
  time_t now = time(0);
  
  struct tm tStruct = *localtime(&now);
  
  char date[100];
  
  strftime(date, sizeof(date), "%c", &tStruct); // i.e. Thu Aug 23 14:55:02 2001
  
  av_dict_set(&pMetaData, "date", date, 0);
  
  av_dict_set(&pMetaData, "creation_time", date, 0);
  
  av_dict_set(&pMetaData, "comment", "This video has been created using Eyeball MSDK", 0);
  
  
  
  // ....................
  
  // .................
  
  
  
  /* write the stream header, if any */
  
  int ret = avformat_write_header(m_pFormatCtx, &pMetaData);

  I also tried to see if the file contains any metadata using mediainfo and exiftools in linux. Also I tried ffmpeg -i output.mov but no metadata is shown.

  Whats the problem ? Is the flags value 0 in av_dict_set okay ? DO I need to set different flags for different platform (windows/linux) ?

  I saw this link and it stated that for windows, I have to use id3v2_version 3 and -write_id3v1 1 to make metadata working. If so, how can I do this in C++ ?