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• Ffmpeg mixing audio only for n number of videos using offset with an altered duration

  26 août 2022, par Turgut

  I want to mix audio stream of n amount of video files with ffmpeg, with certain parameters such as :

  


  

  • Duration : I want to specify how long each audio is going to play for each output. For example if I specify ffmpeg -i -d:5 first.mp4 -i second.mp4 it should play the audio from first.mp4 for 5 seconds (I don't know if -d:5 is a real tag it's just an example I've made ).

  


  • Starting point : I want to specify when a given file is going start on the output, I probably need to use -itsoffset 5 but I don't know if it's the right one in terms of interacting with other commands, in on itself it works fine. For example : ffmpeg -i -isoffset 5 first.mp -i second.mp4 causes the second.mp4 to start immediately, and first.mp4 to start after 5 seconds.

  


  • Segmentation : This is the tricky one, I want to specify at which point the input's audio should start. It's like the -ss flag but the problem is it's not working together with -itsoffset. For example when I say ffmpeg -i -ss 5 first.mp4 -i second.mp4 both files should start immediately on the output, but first.mp4 should start on it's 5 seconds. So the 5th second of first.mp4 is heard at the 1st second of the output.

  


  


  This is what I'm trying to achieve, my problem is that I don't know how to implement 'duration' and -ss is not working together with -itsoffset.

  


  At the end I should have something similar to this :

  


  ffmpeg -y -d 5 -itsoffset 3.5 -i first.mp4 -d 10 -ss 10 -itsoffset 5.3 -i 3 -vn -copyts -async 1 -filter_complex amix=inputs=2 out.mp


  


  Which should result in an audio that sounds like this : The first 3.5 seconds are empty, no audio is heard. Then first.mp4 is heard from it's beginning for 5 seconds. When the outputs timestamp reaches 5.3, the 10th seconds of second.mp4 is heard (while first.mp4 is still playing, it's supposed to play until 8.5, so I should hear both files at the same time.) for 10 seconds.

  


  I can't find an example of this and some sources are out-of date.

  


• avformat/avio : privatize source of truth for AVIOContext::written

  13 octobre 2021, par Jan Ekström

  avformat/avio : privatize source of truth for AVIOContext::written
  Looking at 3f75e5116b900f1428aa13041fc7d6301bf1988a, the field
  
  was supposed to be private, but during merging the field and the
  
  group that had the comment about it got separated.
  Thus, move the actual privately utilized state of this variable
  
  into the private FFIOContext. Additionally, name the private field
  
  somewhat better, so that it does not get confused with the amount
  
  of bytes written out.
  

  • [DH] libavformat/avio_internal.h
  • [DH] libavformat/aviobuf.c

• 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 ?