About headless(ssh remote login) run environment

[Michael.Ma]

There is another solution:
1 EXPORT DISPLAY=.0:0
2 init ogl render to off-screen buffer (MAYBE optional)
3 call ffmpeg transcode command as usually.

test passed on ubuntu18.04 x64

int no_window_init()
{
    glXCreateContextAttribsARBProc glXCreateContextAttribs = NULL;
    glXCreateContextAttribs = 
        (glXCreateContextAttribsARBProc)glXGetProcAddressARB(
            (const GLubyte *)"glXCreateContextAttribsARB");

    const char *displayName = NULL;
    Display *display;
    display = XOpenDisplay(displayName);

    static int visualAttribs[] = {
        GLX_SAMPLE_BUFFERS, 1, GLX_SAMPLES, 4
    };
    int numberOfFramebufferConfigurations = 0;
    GLXFBConfig *fbConfigs;
    fbConfigs = glXChooseFBConfig(
        display, DefaultScreen(display), visualAttribs, &numberOfFramebufferConfigurations);

    int context_attribs[] = {
        GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
        GLX_CONTEXT_MINOR_VERSION_ARB, 0,
        GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_DEBUG_BIT_ARB,
        GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
        None};
    GLXContext glContext[NUM];
    glContext[0] = glXCreateContextAttribs(display, fbConfigs[0], 0, 1, context_attribs);

    GLXPbuffer pbuffer;
    int pbufferAttribs[] = {
        GLX_PBUFFER_WIDTH, 32,
        GLX_PBUFFER_HEIGHT, 32,
        None
    };
    pbuffer = glXCreatePbuffer(display, fbConfigs[0], pbufferAttribs);
    XFree(fbConfigs);
    XSync(display, False);
    glXMakeContextCurrent(display, pbuffer, pbuffer, glContext[0]);

    return 0;
}

static av_cold int init(AVFilterContext *ctx)
{
    GlMirrorContext *gs = ctx->priv;
    if (gs->no_window) {
        av_log(NULL, AV_LOG_ERROR, "open gl no window init ON\n");
        no_window_init();
    }
    
    return glfwInit() ? 0 : -1;
}

[Numberwolf-Yanlong]

Thanks , I recved and will try this week~

You can also submit a pull request for this issue~ ^_^

[BinaryBang]

[Background]
I compiled the ffmpeg on centos,and it worked well with xvfb.
But I find it does not use gpu,and I don't kown the reason.
There is a nvidia video card on my server.
So I want to try the no_window_init solution.

[Question]
When I use the no_window_init,It crashed at glXChooseFBConfig, and the display variable is null after XOpenDisplay.
Is there some additional operation when use no_window_init?

I am looking forward to your advice,thanks very much!