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• How Opensl es on android control the audio speed ?

  6 décembre 2013, par user1882379

  I use NDK+FFMPEG on android to decode an video file, and transfer the decoded pcm data to opensles for play audio .I register the opengles for the pcm format：

    SLDataFormat_PCM format_pcm;
  
      format_pcm.formatType = SL_DATAFORMAT_PCM;
  
      format_pcm.numChannels = channel;
  
      format_pcm.samplesPerSec = rate * 1000;
  
      format_pcm.bitsPerSample = SL_PCMSAMPLEFORMAT_FIXED_16;
  
      format_pcm.containerSize = SL_PCMSAMPLEFORMAT_FIXED_16;

  also I convert the decoded pcm data to AV_SAMPLE_FMT_S16 format using swr_convert(...), but the play audio speed is very fast. but if you use sdl , the play speed is normal. It would be sdl can control the play audio speed, but opensles can not. I do not know whether it is my mistake using opensles or opensles can not control audio speed(need application to control)？

• Revision 1092140379 : No longer use use_lastframe_partitioning speed feature The speedup in rd_pick_p

  6 septembre 2014, par Yunqing Wang

  Changed Paths :
   Modify /vp9/encoder/vp9_speed_features.c

  
  
  No longer use use_lastframe_partitioning speed feature

  The speedup in rd_pick_partition() function makes it possible
  to drop use_lastframe_partitioning feature. By doing that, we
  achieve good PSNR gain with small speed loss. Also, this makes
  encoding loop less complicated. The code cleanup patch will
  follow.

  Borg tests showed :
  1. At speed 2,
  stdhd set : 0.201% PSNR gain, 0.133% SSIM gain ;
  derf set : 0.262% PSNR gain, 0.276% SSIM gain.
  2. At speed 3,
  stdhd set : 0.139% PSNR gain, 0.109% SSIM gain ;
  derf set : 0.447% PSNR gain, 0.442% SSIM gain.

  The average speed loss over selected test clips is within 1%
  with the worst case of 4%.

  Change-Id : Icfd2ded7869372b585a6972855d933b3d0280d90

• Splitting video in short clip result in some being empty ?

  2 décembre 2018, par Édouard Lopez

  I’m trying to split a video (50-100Mo) into several small clips of a few seconds each. I don’t need re-encoding, hence my use of codec copy.

  However some of the resulting clips don’t have any video.

  Fast but no video in some files

  ffmpeg \
  
    -y \
  
    -i ./data/partie-1:-Apprendre-300-mots-du-quotidien-en-LSF.jauvert-laura.hd.mkv \
  
    -ss 0:00:07.00 \
  
    -codec copy \
  
    -loglevel error \
  
    -to 0:00:10.36 \
  
    'raw/0:00:07.00.au revoir.mkv'

  I also tried -map 0 -c copy, -acodec copy -map 0:a -vcodec copy -map 0:v or no option related to codec.

  Slow but complete

  No argument related to audio/video encoding, it’s working but pretty slow.

  ffmpeg -y \
  
    -i "$SOURCE_VIDEO_FILE" \
  
    -ss 0:05:37.69 \
  
    -to 0:05:40.64 \
  
    -loglevel error
  
    'raw/0:05:37.69.pas la peine.mkv'

  Question

  How do I split a video into small chunk ~2-4s when I have no need for re-encoding ?

  related : https://video.stackexchange.com/q/25365/23799