static int thread_init(AVCodecContext *avctx)
{
    int i;
    ThreadContext *c;
    int thread_count = avctx->thread_count;

    if (thread_count <= 1)
        return 0;

    c = av_mallocz(sizeof(ThreadContext));
    if (!c)
        return -1;

    c->workers = av_mallocz(sizeof(pthread_t)*thread_count);
    if (!c->workers) {
        av_free(c);
        return -1;
    }

    avctx->thread_opaque = c;
    c->current_job = 0;
    c->job_count = 0;
    c->job_size = 0;
    c->done = 0;
    pthread_cond_init(&c->current_job_cond, NULL);
    pthread_cond_init(&c->last_job_cond, NULL);
    pthread_mutex_init(&c->current_job_lock, NULL);
    pthread_mutex_lock(&c->current_job_lock);
    for (i=0; i<thread_count; i++) {
        if(pthread_create(&c->workers[i], NULL, worker, avctx)) {
           avctx->thread_count = i;
           pthread_mutex_unlock(&c->current_job_lock);
           ff_thread_free(avctx);
           return -1;
        }
    }

    avcodec_thread_park_workers(c, thread_count);

    avctx->execute = avcodec_thread_execute;
    avctx->execute2 = avcodec_thread_execute2;
    return 0;
}