将ffmpeg管道重定向到子进程

Question

How can I redirect a ffmpeg pipe from a process to the child process stdin?

I want to achieve the same thing as piping in cmd:

ffmpeg -i test.mov pipe:1 | vlc -

I tried:

avio_open("pipe:1"); // ffmpeg open pipe to STD_OUTPUT_HANDLE.

// lots of code

STARTUPINFO si;
PROCESS_INFORMATION pi;

SECURITY_ATTRIBUTES saAttr = {0}; 
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES); 
saAttr.bInheritHandle = TRUE; 
saAttr.lpSecurityDescriptor = NULL; 

CreatePipe(&hReadPipe, &hWritePipe, &saAttr, 0);

SetStdHandle(STD_OUTPUT_HANDLE, hWritePipe);

ZeroMemory(&si, sizeof(si));
ZeroMemory(&pi, sizeof(pi));

si.cb = sizeof(si);
si.dwFlags   = STARTF_USESTDHANDLES;
si.hStdInput = hReadPipe;   

CreateProcess(NULL,   // No module name (use command line)
    L"C:\\Program Files (x86)\\VideoLAN\\VLC\\vlc -vv --demux ffmpeg -",        // Command line
    NULL,           // Process handle not inheritable
    NULL,           // Thread handle not inheritable
    TRUE,          // Set handle inheritance to FALSE
    0,              // No creation flags
    NULL,           // Use parent's environment block
    NULL,           // Use parent's starting directory 
    &si,            // Pointer to STARTUPINFO structure
    &pi )           // Pointer to PROCESS_INFORMATION structure

// start ffmpeg write to file.

But I honestly don't know what I'm doing.

Is there any GetStdHandle that doesn't normally print to the console?

Answer 1

You can try creating a pipe:

1. Call CreatePipe() to create a read handle and a write handle

2. Call SetStdHandle() to make the write handle of the pipe your new stdout

3. Specify the read handle of the pipe as hStdInput to CreateProcess()

Update:

if your application uses printf() to print to the STD output console, you will probably need to hack into the stdout struct and replace the handle there. In any case, try stepping into a printf() call that does not redirected correctly and see which handle it uses in the end.