Using suspendFrame

suspend.cpp

//////////////////////////////////////////
// This file contains a simple filter
// skeleton you can use to get started.
// With no changes it simply passes
// frames through.

#include <thread>
#include <chrono>

#include "VapourSynth.h"
#include "VSHelper.h"

using namespace std::literals;

typedef struct {
    VSNodeRef *node;
    const VSVideoInfo *vi;
} FilterData;

static void VS_CC filterInit(VSMap *in, VSMap *out, void **instanceData, VSNode *node, VSCore *core, const VSAPI *vsapi) {
    FilterData *d = (FilterData *) * instanceData;
    vsapi->setVideoInfo(d->vi, 1, node);
}

static const VSFrameRef *VS_CC filterGetFrame(int n, int activationReason, void **instanceData, void **frameData, VSFrameContext *frameCtx, VSCore *core, const VSAPI *vsapi) {
    FilterData *d = (FilterData *) * instanceData;
    VSSuspensionContext* suspension = nullptr;

    if (activationReason == arInitial) {
        suspension = vsapi->suspendFrame(core, frameCtx);
        try {
            /*
             * Do whatever you want here.
             * 
             * This is just a simple example by creating a thread that just sleeps for
             * 10 seconds before resuming.
             */
            std::thread([suspension, vsapi](){
                std::this_thread::sleep_for(10s);
                vsapi->resumeFrame(suspension);
            }).detach();
        } catch(...) {
            vsapi->setFilterError("Failed to start thread", frameCtx);

            // Cancel the suspension as an error occured while passing the suspension-context
            // to another thread.
            vsapi->cancelSuspend(suspension, frameCtx);
            return 0;
        }
    } else if (activationReason == arResume) {
        vsapi->requestFrameFilter(n, d->node, frameCtx);
    } else if (activationReason == arAllFramesReady) {
        const VSFrameRef *frame = vsapi->getFrameFilter(n, d->node, frameCtx);
        return frame;
    }

    return 0;
}

static void VS_CC filterFree(void *instanceData, VSCore *core, const VSAPI *vsapi) {
    FilterData *d = (FilterData *)instanceData;
    vsapi->freeNode(d->node);
    free(d);
}

static void VS_CC filterCreate(const VSMap *in, VSMap *out, void *userData, VSCore *core, const VSAPI *vsapi) {
    FilterData d;
    FilterData *data;

    d.node = vsapi->propGetNode(in, "clip", 0, 0);
    d.vi = vsapi->getVideoInfo(d.node);

    data = (FilterData*)malloc(sizeof(d));
    *data = d;

    vsapi->createFilter(in, out, "Filter", filterInit, filterGetFrame, filterFree, fmParallel, 0, data, core);
}

//////////////////////////////////////////
// Init

VS_EXTERNAL_API(void) VapourSynthPluginInit(VSConfigPlugin configFunc, VSRegisterFunction registerFunc, VSPlugin *plugin) {
    configFunc("moe.encode.delay", "delay", "Simple Suspend Frame example", VAPOURSYNTH_API_VERSION, 1, plugin);
    registerFunc("Delay", "clip:clip;", filterCreate, 0, plugin);
}