[FFmpeg-devel] custom execute2 access violation?

[Robert Nagy]

Could anyone explain why the following code gets an access violation while
trying to encode DNXHD.

int thread_execute(AVCodecContext* s, int (*func)(AVCodecContext *c2, void
*arg2), void* arg, int* ret, int count, int size)
{
    tbb::parallel_for(0, count, 1, [&](int i)
    {
        int r = func(s, (char*)arg + i*size);
        if(ret)
ret[i] = r;
    });
    return 0;
}

int thread_execute2(AVCodecContext* s, int (*func)(AVCodecContext* c2,
void* arg2, int, int), void* arg, int* ret, int count)
{
    for(int i = 0; i < count; i++)
    {
        int r = func(s, arg, i, 0); // access violation on i == 0. <--
ACCESS VIOLATION HERE
        if(ret)
ret[i] = r;
    }
    return 0;
}

int tbb_avcodec_open(AVCodecContext* avctx, AVCodec* codec)
{
    int ret = avcodec_open(avctx, codec);
    avctx->execute = thread_execute;
    avctx->execute2 = thread_execute2;
    return ret;
}

int tbb_avcodec_close(AVCodecContext* avctx)
{
return avcodec_close(avctx);
}

//void thread_init(AVCodecContext* s)
//{
// static const size_t MAX_THREADS = 16; // See mpegvideo.h
// static int dummy_opaque;
//
//    s->active_thread_type = FF_THREAD_SLICE;
// s->thread_opaque  = &dummy_opaque;
//    s->execute  = thread_execute;
//    s->execute2  = thread_execute2;
//    s->thread_count  = MAX_THREADS; // We are using a task-scheduler, so
use as many "threads/tasks" as possible.
//}
//
//void thread_free(AVCodecContext* s)
//{
// if(!s->thread_opaque)
// return;
//
// s->thread_opaque = nullptr;
//}
//
//int tbb_avcodec_open(AVCodecContext* avctx, AVCodec* codec)
//{
// //CodecID supported_codecs[] = {CODEC_ID_MPEG2VIDEO, CODEC_ID_PRORES,
CODEC_ID_FFV1, CODEC_ID_DNXHD, CODEC_ID_DVVIDEO};
//
// avctx->thread_count = 1;
// if((codec->capabilities & CODEC_CAP_SLICE_THREADS) &&
//  (avctx->thread_type & FF_THREAD_SLICE))
// {
// thread_init(avctx);
// }
// // ff_thread_init will not be executed since thread_opaque != nullptr ||
thread_count == 1.
// return avcodec_open(avctx, codec);
//}
//
//int tbb_avcodec_close(AVCodecContext* avctx)
//{
// thread_free(avctx);
// // ff_thread_free will not be executed since thread_opaque == nullptr.
// return avcodec_close(avctx);
//}