feed.c

static int activate(AVFilterContext *ctx) {
    FeedContext *feed = ctx->priv;
    int ret, status, nb_samples = 0;
    if (!feed->abuf && !feed->vbuf) {
        if (ff_outlink_frame_wanted(feed->ov)) {
            ret = ff_inlink_consume_frame(feed->iv, &feed->vbuf);
            if (ret < 0)
                return ret;
            else if (ret==0) {
                ff_inlink_request_frame(feed->iv);
            }
        }
        if (ff_outlink_frame_wanted(feed->oa)) {
            nb_samples = ff_inlink_queued_samples(feed->ia);
            if (nb_samples > 0 && ff_inlink_check_available_samples(feed->ia, nb_samples) > 0) {
                ret = ff_inlink_consume_samples(feed->ia, nb_samples, nb_samples, &feed->abuf);
                if (ret < 0)
                    return ret;
            }
            else {
                ff_inlink_request_frame(feed->ia);
            }
        }
    }

    if (feed->vbuf) {
        ret = ff_filter_frame(feed->ov,feed->vbuf);
        feed->vbuf = NULL;
        return ret;
    }

    if (feed->abuf) {
        ret = ff_filter_frame(feed->oa,feed->abuf);
        feed->abuf = NULL;
        return ret;
    }

    return 0;
}