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• Adding HEVC reference decoder to ffmpeg framework

  4 mars 2014, par Zax

  I have a tweaked HM reference code of HEVC Decoder based on my requirements. I also know that FFMPEG version 2.1 onwards supports HEVC. But its a necessity for me to integrate my modified HM code.

  Hence I have gone through the post :

  http://wiki.multimedia.cx/index.php?title=FFmpeg_codec_howto

  According to this post, I need to define some functions that are needed to add a new decoder support to FFMPEG framework.

  The structure is : typedef struct AVCodec

  I have defined a structure as shown below :

  AVCodec HMHEVC_decoder =
  
  {
  
      .name           = "hmhevc",
  
      .type           = AVMEDIA_TYPE_VIDEO,
  
      .id             = AV_CODEC_ID_HMHEVC,
  
  
  
      .init           = hmhevc_decode_init,
  
      .close          = hmhevc_decode_close,
  
      .decode         = hmhevc_decode_frame,
  
  };

  However, looking at the other examples, I feel I have to add another variable like :

      .priv_data_size = sizeof(HEVCContext),

  But the problem is that I don't have any such context. So in case I don't define this, what are the things that FFMPEG framework wont provide my decoder ?

  Also is definition of this private data context compulsary ?

  What are the other fields that have to be compulsorily defined ?

  My main intention is that FFPLAY should be able to play the decoded frame.

• Input seeking for frame at specified timestamp with Py-AV

  9 décembre 2019, par neonScarecrow

  I have a project already using Py-AV and am trying to replicate a specific ffmpeg command. The goal is to get a frame roughly around the specified timestamp.

  Here’s the ffmpeg commmand :
  https://trac.ffmpeg.org/wiki/Seeking

  ffmpeg -ss 14 -i https://some_url.mp4 -frames:v 1 frame_at_14_seconds.jpg

  Here’s my code :

      #return one frame around 14 seconds into the movie
  
      target_sec = 14 
  
      container = av.open('https://some_url.mp4', 'r')
  
      container.streams.video[0].thread_type = 'AUTO'
  
      video_stream = next(s for s in container.streams if s.type == 'video')
  
      time_base = float(video_stream.time_base)
  
      target_timestamp = int(target_sec / time_base) + video_stream.start_time
  
      video_stream.seek(target_timestamp)
  
      for frame in container.decode(video_stream):
  
          frame.to_image().save('frame_at_14_seconds.jpg')
  
          break

  Additionally, I have found any documentation about this, but does anyone know if either command (ffmpeg/av.open) is downloading the entire file to a tmp file behind the scenes. I’m looking for a less memory-intensive way to read a frame for every second in an up to 60 second video.

• Need help combining commands in to a script to run in Ubuntu

  17 juin 2020, par user298294

  I have a bunch of video files with DTS audio that I need to convert to AC3. I have found commands that can do different parts of the task but I'm not sure how to put it all together to make a script that works. I have found the following script that will convert the audio from all my files to AC3 however I would prefer for it to only convert the DTS audio files to AC3. The script is as follows.

  



  shopt -s globstar
for f in **/*.mkv; 
do 
    fname="${f##*/}"
    ffmpeg -i "$f" -c:v copy -c:s copy -c:a ac3 "/some/directory/$fname" &&
    mv "/some/directory/$fname" "$f"
done


  



  I have also found this command that will return what sort of audio codec the mkv file is using.

  



  `ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 input.mkv`


  



  So I'm wondering how I can combine the two to create a script that will do what I want it to do. I'm guessing I can add an if function using ffprobe at the beginning of the script ? Something like this...

  



  shopt -s globstar
for f in **/*.mkv; 
do 
    fname="${f##*/}"
    if ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of 
       default=nokey=1:noprint_wrappers=1 "$f" | egrep "DTS"; then
       ffmpeg -i "$f" -c:v copy -c:s copy -c:a ac3 "/some/directory/$fname" &&
       mv "/some/directory/$fname" "$f"
    fi
done


  



  Are there any problems with that ? I haven't written scripts since I was in high school playing around with my graphics calculator because I was bored so any help would be greatly appreciated.