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• In ffmpeg, how to search to a keyframe BEFORE a specified time ?

  12 janvier 2018, par siods333333

  Background

  For a video in the mp4 or flv container formats, I need to :

  1. Get its duration.

  2. Get a keyframe at 25% of its duration. If frame at 25% isn’t a keyframe, seek to the first keyframe before that frame.

  3. Seek to audio at 10ms before that keyframe.

  According to the following comment on StackOverflow, av_seek_frame seems to only seek to a keyframe after a specified time.

  Question

  Given that it appears I can only seek after a specified time, how is it possible to get the required keyframe and to seek to the correct part in a mp4 or flv container as specified above ?

  My Ideas

  • My best bet is probably parsing the header (and index, where applicable) manually, and then use the av_seek_frame with the AVSEEK_FLAG_BYTE flag.

  • Or I can just walk the whole file, and just check if AVFrame->key_frame is true or not.

  It would be awesome if the trim filter could support different seek methods, but I guess I have to get correct timestamps by myself, is that correct ?

• tests/checkasm : fix wrong summation of bench time

  31 mars, par Niklas Haas

  tests/checkasm : fix wrong summation of bench time
  This was changed 8 years ago with the introduction of the linux-perf path,
  
  with seemingly no justification at the time. Likely a developer oversight
  
  from testing.
  This bug not only made —runs completely ineffective, but also meant that we
  
  didn't actually correctly filter out outliers.
  Fixes : e0d56f097f42bcdbe6c3b2f57df62a4da63f2094
  

  • [DH] tests/checkasm/checkasm.h

• Cutting the stream on local date time when scheduled

  19 juin 2017, par Fearhunter

  I am using a ffmpeg slice commando in my C# code. For example : I scheduled a stream from 12pm till 3 pm. In my if statement I use a condition to compare the local datetime with the time of now.

   DateTime systemDate = DateTime.Now;
  
   DateTime compareDate = DateTime.Today;
  
  
  
    private Process SliceStream(string url)
  
          {
  
              if (systemDate < compareDate)
  
              {
  
                  return Process.Start(new ProcessStartInfo
  
                  {
  
                      FileName = "ffmpeg.exe",
  
                      Arguments = $"-i \"{url}\"-acodec aac -strict -2 -vcodec libx264 -hls_wrap 100 -f hls -hls_time 20 C:/var/1.m3u8 ",
  
                      UseShellExecute = false,
  
                      RedirectStandardOutput = true
  
  
  
                  });
  
              }
  
              else
  
              {
  
                  Thread.Sleep(100);
  
                  return null;
  
              }
  
          }

  The problem is it doesn’t work when my time on my computer is for example 12pm and he is not cutting the stream.

  What am I doing wrong ?