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• ffmpeg output seeking not accurate even after -i [closed]

  3 septembre 2023, par hl037_

  In the documentation of ffmpeg, it is stated that if -ss is passed after -i, then it is frame accurate (Other questions are for -ss before -i).

  


  Here is my command :

  


  ffmpeg -i vid.mkv -ss 53 -codec copy test.mkv -y 


  


  However, it is still not accurate, and seems to jump to the nearest keyframe. Am i missing something ?

  


  Note : the problem only occurs when the video steam is copied. If reencoded or discarded, it works as expected

  


  Note2 (As I am doing other tries) : There are also strange things with audio :

  


  ffmpeg -i vid.mkv -ss 53 -codec copy test1.mkv -y 
ffmpeg -i vid.mkv -ss 54 -codec copy test2.mkv -y 
ffmpeg -i test1.mkv -vn -c:a copy test1a.mkv -y
ffmpeg -i test2.mkv -vn -c:a copy test2a.mkv -y


  


  

  • test1.mkv is reported to be the right lenght, but the first frame correspond to the frame at 0:50 in original (end is good)

  


  • test2.mkv is reported to be the right lenght, but the first frame correspond to the frame at 0:55 in original (end is good)

  


  • test1a.mkv is the expected audio (starts at 0:53 of the original)

  


  • test2a.mkv is the expected audio (starts at 0:54 of the original)

  


  


• Video converter library for Android [closed]

  17 décembre 2019, par Sushant

  I am trying to convert video formats by using FFmpeg. I’ve converted video from mp4 to mkv but it’s increasing the file size. Are there any good video trans-coding libraries that can be recommended ?

• How would I dynamically link FFmpeg in a C# Project for use with FFMpegCore ?

  15 octobre 2024, par liamliam

  So far, I have FFMpegCore working in my project with a ffmpeg.exe dropped into the project directory. This works, but for LGPL license compliance FFmpeg requires dynamic linking :
  
Use dynamic linking (on windows, this means linking to dlls) for linking with FFmpeg libraries..

  


  While I understand the basic concept of dynamic vs static linking, my problem is likely a misunderstanding of how .dlls work and how they apply to C# and .NET.
  
Would it be possible to compile ffmpeg into a single .dll that could be accessed by FFMpegCore cross-platform ? From what I can gather in the source, FFMpegCore looks for an ffmpeg or ffmpeg.exe file in its configuration path.

  


  Is it possible to have .NET dynamically link FFmpeg and expose it to libraries for use or is that a complete misunderstanding and would I then need a wrapper library with different capabilities ?

  


  I've attempted to find the answer in the relevant documentation, but I found none for this specific use of either library. I suspect my problem might be a fundamental misunderstanding of how these tools work and work together.
My ideal result would be using FFMpegCore with an FFmpeg.dll that works cross-platform instead of the .exe.

  


  Edit 1 : @taratect's answer and graphic sent me down a path that cleared up quite a bit about exes and dlls. .Net compiles source code down to platform agnostic Intermediate Language in the form of a .dll or .exe(completely different to C++ variants of these files), which is executed by the Common Language Runtime using a Just In Time compiler to convert that Intermediate Language to Machine Code that can be run on the specific platform .Net is installed on. C++(FFmpeg) compiles directly to platform specific Machine Code (as shown in the graphic), confusingly in the form of a .dll or .exe (on Windows). .Net can indeed load and run machine code unmanaged by Common Language Runtime, since everything is run as Machine Code by the end, however memory and other complexities must then be managed by me, which seems to be what FFMpegCore does in wrapping the executable. I might still be confused/incorrect on some of this, unmanaged code is beyond my understanding so far.
This does more or less confirm that FFMpegCore probably can't be expected to use FFmpeg in the way I hoped and a better workaround might be having the user just supply an FFmpeg source or implement a downloader as part of installation so that I don't have to redistribute it at all.