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• avformat/utils : estimate_timings_from_pts - increase retry counter, fixes invalid...

  15 novembre 2015, par Rainer Hochecker

  avformat/utils : estimate_timings_from_pts - increase retry counter, fixes invalid duration for ts files with hevc codec
  Fixes a mpegts file with hevc that fails estimating duration. Increasing number of
  
  retries fixes the issue.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/utils.c

• Why is there ffmpeg codec noise when encoding test tone ?

  27 février 2017, par JackOfAllTrades

  I used FFmpeg to generate a test clip with color bars and a tone. I also made a special filter to dump out the raw audio data to check it. I was surprised to find that there is significant noise riding on the audio tone after it has gone through the AAC codec. Is this expected ? Is there a way to prevent it ?

  To make the test file I used :

  ffmpeg -f lavfi -i "smptehdbars=duration=600:size=1280x720:rate=59.94" -qscale:v 1 -pix_fmt yuv420p smpte_r59_720.mp4

  then

  ffmpeg -i smpte_r59_720.mp4 -f lavfi -i "sine=frequency=1000:sample_rate=48000:duration=600" -qscale:v 1 -vcodec copy -c:a aac -b:a 192k -shortest -map 0:0 -map 1:0 smpte_r59_720T.mp4

  and then

  ffmpeg -i smpte_r59_720T.mp4 -y -map 0 -acodec aac -vcodec libx264 -crf 23 -bsf:v h264_mp4toannexb smpte_r59_720T.ts

  (Trying to do this all in one step kept failing.)

  Other variations on this have varying degrees of noise, sometimes above nominal amplitude and sometimes below.

  After finding this problem I pulled a third party test tone .WAV file with 44.1KHz sample rate from the web and checked it. The raw file is clean, but the encoded file I made has noise.

  Noise on TS SMPTE bars

  Clean audio from MP4

• Maintaining Video Quality and Size while processing with FFmpeg

  2 février 2017, par Syeda Zunairah

  I am using FFmpeg for video watermarking in android. Everything is working good but now I have to choose one from Video Quality and Video Size but I need to take care of both.

  Here is my code

   MediaMetadataRetriever mediaMetadataRetriever = new MediaMetadataRetriever();
  
   mediaMetadataRetriever.setDataSource(videoPathtem);
  
  String bitRate = mediaMetadataRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_BITRATE);
  
  String cmd = "-y -i " + videoPathtem + " -i " + watermarkImagePath + " -b:v " + bitRate + " -filter_complex overlay=0:0 -strict -2 -metadata:s:v:0 rotate=" + videoRotation + " -preset ultrafast " + resultVideoPath;

  Now if I don’t define the bitrate in the above command the Video Quality is maintaining but the bitrate is increasing with X5 (i.e. if original bitrate was 1000bps now its 5000kbps almost) resulting too much increase in video size (i.e from 50 MB to 150MB)

  But if I define the bitrate in the above command than the bitrate and video size is almost like the original which is perfect but the quality of the video is too low.

  Now is there any way I can maintain the quality as well as video size ?

  I have searched on SO and checked other answers but nothing seems to handle both.

  Thanks.