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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.

• mov : Export geotag metadata fields

  3 juin 2014, par Martin Storsjö

  mov : Export geotag metadata fields
  The ’ ?xyz’ form is used by android devices (and according to apple
  
  mailing list archives, also by older iOS devices). The ’loci’ field
  
  (defined in 3GPP 26.244) is used by recent iOS devices.
  Even though the loci field can contain an altitude, it was plain
  
  0 in my sample. Just export longitude and latitude, in a string
  
  format matching the one used by the ’ ?xyz’ metadata field.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/mov.c