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• avformat/matroskaenc : Remove unnecessary avio_tell(), avio_seek()

  22 janvier 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Remove unnecessary avio_tell(), avio_seek()
  avio_close_dyn_buf() has a bug : When the write pointer does not point to
  
  the end of the written data when calling it (i.e. when one has performed
  
  a seek back to update already written data), it would not add padding to
  
  the end of the buffer, but to the current position, overwriting other
  
  data ; furthermore the reported size would be wrong (off by the amount of
  
  data it has overwritten with padding).
  In order not to run into this when updating already written elements or
  
  elements for which size has only been reserved, the Matroska muxer would
  
  first record the current position of the dynamic buffer, then seek to
  
  the desired position, perform the update and seek back to the earlier
  
  position.
  But now that end_ebml_master_crc32() does not make use of
  
  avio_close_dyn_buf() any more, this is no longer necessary.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• what is a steps to apply filter to video using ffmpeg c program android ndk

  13 juillet 2016, par Rajkumar

  I am newbie to ffmpeg with android. i have an input video birds.mp4 that have following settings

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'birds.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf54.59.106
  
    Duration: 00:00:21.60, start: 0.000000, bitrate: 574 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 320x176 [
  
  SAR 44:45 DAR 16:9], 440 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, flt
  
  p, 127 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  i have compiled ffmpeg as *.so file for android. And i write a Jni wrapper. Now i want to apply a filter to that input video and save it to output.mp4 with same setting as shown. i know basic terminologies encoding, decoding, muxing, transcoding.
  I want to know How to do this task ? and What are the techniques involved to do this task ?

  I use ffmpeg-3.1 c-source code grabbed from github. i refer this sample it doesn’t guide me.

  If anybody experienced this problem please guide me right direction.

• Faster Thumbnail/Image Extraction from Video using FFMPEG ?

  17 juillet 2019, par Arif Nadeem

  I am using this command to extract a series of images from a video to express them as a visual time-frame of the video.

  ffmpeg -i inputfile.mp4  -r  1  -t  12  image-%d.jpeg

  Most of my videos are in mp4 format. I am able to extract the images successfully but the time taken for extraction is too long.

  Is there any way I could reduce the time for image extraction ?

  EDIT : It is taking me 60 secs to get 8 thumbnails from a 15 sec long video encoded in MP4 format, I am doing this operation on my Galaxy Nexus(Android Phone) is there any way to improve the speed of operation, ideally I want it be less than  10secs.