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• Diference between pkt_duration and pkt_duration_time in ffprobe

  16 décembre 2016, par albertoiNET

  When I execute next ffprobe command in an HLS stream with parameter to show frames in specific stream video in flat format and grep with ’pkt’ pattern, it returns this info :

  $ ffprobe -i http://xxxxxxxxxxxxxxxx/PCMDY_SUB.m3u8 -show_frames -select_streams v:0 -print_format flat | grep pkt
  
  ...
  
  frames.frame.229.pkt_pts=2438664735,
  
  frames.frame.229.pkt_pts_time=27096.274833,
  
  frames.frame.229.pkt_dts=2438664735,
  
  frames.frame.229.pkt_dts_time=27096.274833,
  
  frames.frame.229.pkt_duration=3600,
  
  frames.frame.229.pkt_duration_time="0.040000",
  
  frames.frame.229.pkt_pos=13348,
  
  frames.frame.229.pkt_size=2510,
  
  
  
  frames.frame.230.pkt_pts=2438668335,
  
  frames.frame.230.pkt_pts_time=27096.314833,
  
  frames.frame.230.pkt_dts=2438668335,
  
  frames.frame.230.pkt_dts_time=27096.314833,  
  
  frames.frame.230.pkt_duration=3600,
  
  frames.frame.230.pkt_duration_time="0.040000",
  
  frames.frame.230.pkt_pos=15980,
  
  frames.frame.230.pkt_size=2389,
  
  ...

  What is the difference between info with _time pattern and without it ?.

  I supposed that pkt_duration are in microseconds, and pkt_duration_time is in seconds. It’s true ?

• Convert .flac to .mp3 with ffmpeg, avoid small silence ?

  19 septembre 2017, par RocketNuts

  I’m converting a bunch of .flac audio samples to .mp3 with ffmpeg. Some of these samples are supposed to loop, i.e. the end of the sample fits seamlessly to the beginning (no tick).

  Now no matter how high the mp3 quality setting I use, I keep getting about 0.05 sec of silence at the beginning of the resulting .mp3 which is not there in the original flac.

  Here’s a zoomed in Audacity view of the beginning and ending of both audio samples :

  Original flac :

  

  Notice how the beginning and ending are both ’flat’, so they fit smoothly.

  Converted to mp3 :

  

  Notice how there is now suddenly a 0.05 sec silence, and the end doesn’t end exactly flat (on the baseline). Hence they don’t fit, and the tick and silence are clearly audible when playing in a loop.

  I’m using this for the conversion :

  ffmpeg -i foo.flac -acodec libmp3lame -ab 320k bar.mp3

  or this : (with the -q:a VBR setting)

  ffmpeg -i foo.flac -acodec libmp3lame -q:a 0 bar.mp3

  Either -q:a 0 or -ab 320k is supposed to give the highest possible quality, but I can’t get rid of that strange silence in the beginning and small cutoff at the end, which causes a tick when playing in a loop.

• Use specific channels from specific streams for the final stream using FFMPEG [closed]

  9 juin 2024, par Kazu-kun

  I want to create a 5.1ch audio stream from a 2ch audio stream. However I want to put a negative delay to LFE, SL and SR channels since they will be played from my bluetooth speaker, so I want to make up for the delay by giving it a negative delay.

  


  


  ffmpeg -itsoffset 0.1 -i input.mkv -i input.mkv

  


  -filter_complex “

  


  [1:a]pan=5.1(side)|FL=FL|FR=FR|LFEp>


  [0:a]pan=5.1(side)|FL=FL|FR=FR|LFEp>


  [orig5_1][delayed5_1]amerge=inputs=2,pan=5.1(side)|FL=c6|FR=c7|LFE=c2|SL=c3|SR=c4[a]”

  


  -map "[a]" -map 0:v -map 0:s -c:v copy -c:a flac -c:s copy output.mkv

  


  


  I tried taking the same input twice with the first one being delayed by 0.1 secs. With the delayed input a 5.1 audio is created and with the original another 5.1 audio is created as well. Then the two audio streams are merged with amerge and combined into a single 5.1 audio by taking delayed channels for FL and FR(These will be played from my MacBook) and by taking original channels for LFE, SL and SR(These will be played from my bluetooth JBL). Finally the video and subs streams are taken from the delayed.

  


  The above command gave a "pipe pipe pipe dqoute" error and when I entered the command again it said :

  


  


  zsh : unknown file attribute : i

  


  zsh : no such file or directory : FL+FR

  


  zsh : unknown file attribute : i

  


  zsh : no such file or directory : FL+FR

  


  zsh : unknown file attribute : i

  


  zsh : command not found : -map

  


  


  Please give me a command for my requirement !