ffmpeg-vscode

0. Reference

• MSYS2: http://www.msys2.org/
• pacman mirror: https://lug.ustc.edu.cn/wiki/mirrors/help/msys2
• pacman proxy: https://stackoverflow.com/questions/29783065/msys2-pacman-cant-update-packages-through-corporate-firewall
• FFmpeg: https://github.com/FFmpeg/FFmpeg
• MinGW/FFmpeg installation guide: https://trac.ffmpeg.org/wiki/CompilationGuide/MinGW
• VSCode: https://code.visualstudio.com/
• C/C++ for VSCode: https://code.visualstudio.com/docs/languages/cpp
• Using MinGW and Cygwin with Visual C++ and Open Folder: https://blogs.msdn.microsoft.com/vcblog/2017/07/19/using-mingw-and-cygwin-with-visual-cpp-and-open-folder/

1. Prepare MinGW environment

a. download and install MSYS2 in default path

C:\msys64

b. set up pacman (msys2 package manager) mirror (Optional)

• edit /etc/pacman.d/mirrorlist.mingw32, add below line at the begining：

Server = http://mirrors.ustc.edu.cn/msys2/mingw/i686

• edit /etc/pacman.d/mirrorlist.mingw64, add below line at the begining：

Server = http://mirrors.ustc.edu.cn/msys2/mingw/x86_64

• edit /etc/pacman.d/mirrorlist.msys, add below line at the begining：

Server = http://mirrors.ustc.edu.cn/msys2/msys/$arch

c. set up pacman proxy (Optional)

• open file: C:\msys64\etc\profile
• add below lines at the end of file

export http_proxy=<myusername>:<mypassword>@proxy-host-name:8080
export https_proxy=$http_proxy
export ftp_proxy=$http_proxy
export socks_proxy=$http_proxy
export rsync_proxy=$http_proxy
export no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"

• note 1: myusername and mypassword can be optional
• note 2: example of proxy-host-name: http://xxx.xxx.com

d. update pacman database

pacman -S -y -u

or

pacman -Syu

e. install neccessary tools for building ffmpeg

pacman -S git 
pacman -S make diffutils nasm yasm
pacman -S mingw-w64-x86_64-gcc
pacman -S mingw-w64-i686-gcc

2. Install Visual Studio Code

a. download and install vscode from this link

b. install vscode extensions

C/C++
Code Outline
Code Navigation
vscode-icons

3. Build ffmpeg

a. open mingw64 terminal

cd c:\msys64
mingw64.exe

b. get ffmpeg source code

cd ~
git clone https://github.com/FFmpeg/FFmpeg.git

c. locate ffmpeg source code folder in mingw64 terminal

cd ~/FFmpeg
./configure --enable-debug=3 --disable-optimizations
make -j8

build x264/x265 with ffmpeg

sudo apt install libx264-dev libx265-dev

cd ~/FFmpeg
./configure --enable-debug=3 --disable-optimizations --enable-libx264 --enable-libx265 --enable-gpl
make -j8

d. below ffmpeg binaries will be generated at current folder

ffmpeg_g.exe
ffmpeg.exe
ffprobe_g.exe
ffprobe.exe

4. Debug ffmpeg code

a. open ffmpeg source code folder with vscode

b. copy a video file test.mp4

c. set vscode lauch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/ffmpeg_g.exe",
            "args": [
                "-hwaccel",
                "dxva2",
                "-i",
                "test.mp4",
                "tmp.yuv",
                "-y"
            ],
            "stopAtEntry": true,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": true,
            "MIMode": "gdb",
            "miDebuggerPath": "C:\\msys64\\mingw64\\bin\\gdb.exe",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
        }
    ]
}

d. start vscode debug

• switch vscode to debug pannel and click Start Debugging button
• ffmpeg will break at entry of main() function
• set a break point at ff_dxva2_common_end_frame in dxva2.c

int ff_dxva2_common_end_frame(AVCodecContext *avctx, AVFrame *frame,
                              const void *pp, unsigned pp_size,
                              const void *qm, unsigned qm_size,
                              int (*commit_bs_si)(AVCodecContext *,
                                                  DECODER_BUFFER_DESC *bs,
                                                  DECODER_BUFFER_DESC *slice))
{
    // ...

#if CONFIG_D3D11VA
    if (ff_dxva2_is_d3d11(avctx))
        hr = ID3D11VideoContext_SubmitDecoderBuffers(D3D11VA_CONTEXT(ctx)->video_context,
                                                     D3D11VA_CONTEXT(ctx)->decoder,
                                                     buffer_count, buffer11);
#endif
#if CONFIG_DXVA2
    if (avctx->pix_fmt == AV_PIX_FMT_DXVA2_VLD) {
        DXVA2_DecodeExecuteParams exec = {
            .NumCompBuffers     = buffer_count,
            .pCompressedBuffers = buffer2,
            .pExtensionData     = NULL,
        };
        hr = IDirectXVideoDecoder_Execute(DXVA2_CONTEXT(ctx)->decoder, &exec);
    }
#endif
    if (FAILED(hr)) {
        av_log(avctx, AV_LOG_ERROR, "Failed to execute: 0x%x\n", (unsigned)hr);
        result = -1;
    }
}

5. Screenshot