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• Building ffmpeg libraries for third party usage

  23 mars 2023, par mikeProgrammer

  I am trying to create bindings for FFmpeg in Elixir programming language and would love to handle FFmpeg binaries for users of my library.

  


  The whole flow is as follows :

  


  

  1. Write some function definition in Elixir

  


  2. Implement it in in C using ffmpeg libs

  


  3. Compile C code as shared library

  


  4. When running application, Erlang Virtual Machine will load my dynamic library

  


  


  The question is how to compile and include ffmpeg libs in my shared lib so that users of my Elixir lib don't have to install any native dependencies.

  


  Here is what I was trying :

  


  


  1. Compile ffmpeg libs as shared ones. When my Elixir lib is compiling, it downloads precompiled ffmpeg archive, extracts its content and links to it when compiling native functions. I realized that this still won't work as ffmpeg shared libs depend on other shared libs that user has to install on their own.

     


  


  2. Compile ffmpeg libs as static ones and include them in my native shared library using —whole-archive linker option. Here I am getting

     


  


  


  /usr/bin/ld : ffmpeg_build/lib/libavcodec.a(vp9lpf_16bpp.o) : warning : relocation against ff_pw_1' in read-only section .text'
/usr/bin/ld : ffmpeg_build/lib/libavcodec.a(cavsdsp.o) : relocation R_X86_64_PC32 against symbol `ff_pw_5' can not be used when making a shared object ; recompile with -fPIC
/usr/bin/ld : final link failed : bad value
collect2 : error : ld returned 1 exit status

  


  The command I am using

  


  cc -fPIC -I/home/michal/.asdf/installs/erlang/25.1/erts-13.1/include -Iffmpeg_build/include -Ic_src/xav -shared -DXAV_DEBUG=1 c_src/xav/xav_nif.c c_src/xav/reader.c c_src/xav/utils.c -o /home/michal/Repos/xav/_build/test/lib/xav/priv/libxav.so -Lffmpeg_build/lib -Wl,--whole-archive -lavcodec -lswscale -lavutil -lavformat -Wl,--no-whole-archive


  


  FFmpeg configuration

  


  ./configure \
--prefix="$PWD/ffmpeg_build" \
--extra-cflags="-fPIC -I$PWD/ffmpeg_build/include" \
--extra-ldflags="-L$PWD/ffmpeg_build/lib" \
--enable-pic
--disable-programs


  


  Does anything that I am trying to do make sense to you ?

  


  When I am installing ffmpeg-libs package on Fedora, it depends on other shared libs that are automatically downlaoded but what I would love to achieve is to provide self-contained ffmpeg build that can be used in other shared libraries.

  


• Merge (concat) all video file present in '43. DP (Part1)' and put it into '43. DP (Part1)' and give name merged (concat) file to folder name

  29 mars 2024, par Anu Mau

  I have parent folder alpha part 3 which contain child folder 43. DP (Part1), 44. DP (Part2), 45. DP (Part3).

  


  I want to merge (concat) all video file present in 43. DP (Part1) and put it into 43. DP (Part1) and give name merged (concat) file to folder name.

  


  And as it is do for all.

  


  alpha part 3
├── 43. DP (Part1)
│   ├── _43.1_Introduction to DP.mp4
│   ├── _43.2_What is DP_ (Definition).mp4
│   ├── _43.3_Ways of DP.mp4
│   ├── _43.4_7 Important Concepts.mp4
│   ├── _43.5_Climbing Stairs (Recursion).mp4
│   ├── _43.6_Climbing Stairs (Memoization DP).mp4
│   ├── _43.7_Climbing Stairs Variation.mp4
│   └── _43.8_Climbing Stairs (Tabulation DP).mp4
├── 44. DP (Part2)
│   ├── _44.1_Types of Knapsack problems.mp4
│   ├── _44.2_0-1 Knapsack (Recursion).mp4
│   ├── _44.3_0-1 Knapsack (Memoization).mp4
│   ├── _44.4_0-1 Knapsack (Tabulation).mp4
│   ├── _44.5_Target Sum Subset (Tabulation).mp4
│   ├── _44.6_Target Sum Subset (Code).mp4
│   └── _44.7_Unbounded Knapsack (Tabulation).mp4
├── 45. DP (Part3)
│   ├── _45.1_Coin Change (Live Class).mp4
│   ├── _45.2_Rod Cutting.mp4
│   ├── _45.3_Longest Common Subsequence (Recursion).mp4
│   ├── _45.4_LCS (Memoization).mp4
│   └── _45.5_LCS (Tabulation).mp4



  


  Right or is any way to go this at once. Write Python code with FFmpeg.

  


  My Python code is as follows ; what do I need to adjust ?

  


  import os
import subprocess

# Function to merge videos in a folder
def merge_videos_in_folder(folder_path):
    print(f"Merging videos in folder: {folder_path}")

    # Use FFmpeg to concatenate all video files within the folder
    cmd = [
        "ffmpeg",
        "-f", "concat",
        "-safe", "0",
        "-i", "<(find '{}' -type f -name '*.mp4' -exec echo 'file {{}}' \;)".format(folder_path),
        "-c", "copy",
        os.path.join(folder_path, "merged_video.mp4")
    ]
    subprocess.run(cmd, capture_output=True, text=True)

    print(f"Videos merged for folder: {folder_path}")

# Specify the directory containing folders with video files
parent_dir = "/path/to/parent_directory"

# Loop through each folder in the input directory
for folder in os.listdir(parent_dir):
    folder_path = os.path.join(parent_dir, folder)
    if os.path.isdir(folder_path):
        # Merge videos in the current folder
        merge_videos_in_folder(folder_path)

print("All videos merged successfully!")


  


• lavf : ignore attachment streams for interleaving purposes

  20 janvier 2014, par Anton Khirnov

  lavf : ignore attachment streams for interleaving purposes
  Those streams should never get any packets by definition.
  

  • [DBH] libavformat/avformat.h
  • [DBH] libavformat/internal.h
  • [DBH] libavformat/mux.c
  • [DBH] libavformat/options.c
  • [DBH] libavformat/utils.c