Android IjkPlayer解决RTSP延时300ms左右

简介

在上一篇《ijkplayer编译-RTSP》中介绍了，ijkplayer如何进行编译成so库的，以及如何开启rtsp。那么实际在使用的时候会发现延迟不是一般的大。
现在来介绍一下如何解决这个延迟的，经过测试延迟时间可以控制在500ms左右。

修改ijkplayer源码的ff_ffplay.c文件

路径是在ijkplayer-android/ijkmedia/ijkplayer/ff_ffplay.c

修改其中packet_queue_get_or_buffering方法 如下：

注意：注释掉的是原来的代码。

static int packet_queue_get_or_buffering(FFPlayer *ffp, PacketQueue *q, AVPacket *pkt, int *serial, int *finished)
{
//    assert(finished);
//    if (!ffp->packet_buffering)
//        return packet_queue_get(q, pkt, 1, serial);

    while (1) {
//        int new_packet = packet_queue_get(q, pkt, 0, serial);
        int new_packet = packet_queue_get(q, pkt, 1, serial);
        if (new_packet < 0) {
            new_packet = packet_queue_get(q, pkt, 0, serial);
            if(new_packet < 0)
                return -1;
//            return -1;
        }else if (new_packet == 0) {
//            if (q->is_buffer_indicator && !*finished)
            if (!finished)
                ffp_toggle_buffering(ffp, 1);
            new_packet = packet_queue_get(q, pkt, 1, serial);
            if (new_packet < 0)
                return -1;
        }

        if (*finished == *serial) {
            av_packet_unref(pkt);
            continue;
        }
        else
            break;
    }

    return 1;
}

修改此处方法编译测试发现视频播放还是存在一秒左右的延时，达不到预计效果，则继续修改vp_duration方法 ，如下：

static double vp_duration(VideoState *is, Frame *vp, Frame *nextvp) {
    /*if (vp->serial == nextvp->serial) {
        double duration = nextvp->pts - vp->pts;
        if (isnan(duration) || duration <= 0 || duration > is->max_frame_duration)
            return vp->duration;
        else
            return duration;
    } else {
        return 0.0;
    }*/
    return vp->duration;
}

直接return vp->duration；,在修改ffplay_video_thread方法：

static int ffplay_video_thread(void *arg)
{
    FFPlayer *ffp = arg;
    VideoState *is = ffp->is;
    AVFrame *frame = av_frame_alloc();
    double pts;
    double duration;
    int ret;
    AVRational tb = is->video_st->time_base;

//    AVRational frame_rate = av_guess_frame_rate(is->ic, is->video_st, NULL);
    int64_t dst_pts = -1;
    int64_t last_dst_pts = -1;
    int retry_convert_image = 0;
    int convert_frame_count = 0;

#if CONFIG_AVFILTER
    AVFilterGraph *graph = avfilter_graph_alloc();
    AVFilterContext *filt_out = NULL, *filt_in = NULL;
    int last_w = 0;
    int last_h = 0;
    enum AVPixelFormat last_format = -2;
    int last_serial = -1;
    int last_vfilter_idx = 0;
    if (!graph) {
        av_frame_free(&frame);
        return AVERROR(ENOMEM);
    }

#else
    ffp_notify_msg2(ffp, FFP_MSG_VIDEO_ROTATION_CHANGED, ffp_get_video_rotate_degrees(ffp));
#endif

    if (!frame) {
#if CONFIG_AVFILTER
        avfilter_graph_free(&graph);
#endif
        return AVERROR(ENOMEM);
    }

    for (;;) {
        ret = get_video_frame(ffp, frame);
        if (ret < 0)
            goto the_end;
        if (!ret)
            continue;

        if (ffp->get_frame_mode) {
            if (!ffp->get_img_info || ffp->get_img_info->count <= 0) {
                av_frame_unref(frame);
                continue;
            }

            last_dst_pts = dst_pts;

            if (dst_pts < 0) {
                dst_pts = ffp->get_img_info->start_time;
            } else {
                dst_pts += (ffp->get_img_info->end_time - ffp->get_img_info->start_time) / (ffp->get_img_info->num - 1);
            }

            pts = (frame->pts == AV_NOPTS_VALUE) ? NAN : frame->pts * av_q2d(tb);
            pts = pts * 1000;
            if (pts >= dst_pts) {
                while (retry_convert_image <= MAX_RETRY_CONVERT_IMAGE) {
                    ret = convert_image(ffp, frame, (int64_t)pts, frame->width, frame->height);
                    if (!ret) {
                        convert_frame_count++;
                        break;
                    }
                    retry_convert_image++;
                    av_log(NULL, AV_LOG_ERROR, "convert image error retry_convert_image = %d\n", retry_convert_image);
                }

                retry_convert_image = 0;
                if (ret || ffp->get_img_info->count <= 0) {
                    if (ret) {
                        av_log(NULL, AV_LOG_ERROR, "convert image abort ret = %d\n", ret);
                        ffp_notify_msg3(ffp, FFP_MSG_GET_IMG_STATE, 0, ret);
                    } else {
                        av_log(NULL, AV_LOG_INFO, "convert image complete convert_frame_count = %d\n", convert_frame_count);
                    }
                    goto the_end;
                }
            } else {
                dst_pts = last_dst_pts;
            }
            av_frame_unref(frame);
            continue;
        }

#if CONFIG_AVFILTER
        if (   last_w != frame->width
            || last_h != frame->height
            || last_format != frame->format
            || last_serial != is->viddec.pkt_serial
            || ffp->vf_changed
            || last_vfilter_idx != is->vfilter_idx) {
            SDL_LockMutex(ffp->vf_mutex);
            ffp->vf_changed = 0;
            av_log(NULL, AV_LOG_DEBUG,
                   "Video frame changed from size:%dx%d format:%s serial:%d to size:%dx%d format:%s serial:%d\n",
                   last_w, last_h,
                   (const char *)av_x_if_null(av_get_pix_fmt_name(last_format), "none"), last_serial,
                   frame->width, frame->height,
                   (const char *)av_x_if_null(av_get_pix_fmt_name(frame->format), "none"), is->viddec.pkt_serial);
            avfilter_graph_free(&graph);
            graph = avfilter_graph_alloc();
            if ((ret = configure_video_filters(ffp, graph, is, ffp->vfilters_list ? ffp->vfilters_list[is->vfilter_idx] : NULL, frame)) < 0) {
                // FIXME: post error
                SDL_UnlockMutex(ffp->vf_mutex);
                goto the_end;
            }
            filt_in  = is->in_video_filter;
            filt_out = is->out_video_filter;
            last_w = frame->width;
            last_h = frame->height;
            last_format = frame->format;
            last_serial = is->viddec.pkt_serial;
            last_vfilter_idx = is->vfilter_idx;
//            frame_rate = av_buffersink_get_frame_rate(filt_out);
            SDL_UnlockMutex(ffp->vf_mutex);
        }

        ret = av_buffersrc_add_frame(filt_in, frame);
        if (ret < 0)
            goto the_end;

        while (ret >= 0) {
            is->frame_last_returned_time = av_gettime_relative() / 1000000.0;

            ret = av_buffersink_get_frame_flags(filt_out, frame, 0);
            if (ret < 0) {
                if (ret == AVERROR_EOF)
                    is->viddec.finished = is->viddec.pkt_serial;
                ret = 0;
                break;
            }

            is->frame_last_filter_delay = av_gettime_relative() / 1000000.0 - is->frame_last_returned_time;
            if (fabs(is->frame_last_filter_delay) > AV_NOSYNC_THRESHOLD / 10.0)
                is->frame_last_filter_delay = 0;
            tb = av_buffersink_get_time_base(filt_out);
#endif
            //duration = (frame_rate.num && frame_rate.den ? av_q2d((AVRational){frame_rate.den, frame_rate.num}) : 0);
            duration = 0.01;//直接修改duration 等于0.01即可
            pts = (frame->pts == AV_NOPTS_VALUE) ? NAN : frame->pts * av_q2d(tb);
            ret = queue_picture(ffp, frame, pts, duration, frame->pkt_pos, is->viddec.pkt_serial);
            av_frame_unref(frame);
#if CONFIG_AVFILTER
        }
#endif

        if (ret < 0)
            goto the_end;
    }
 the_end:
#if CONFIG_AVFILTER
    avfilter_graph_free(&graph);
#endif
    av_log(NULL, AV_LOG_INFO, "convert image convert_frame_count = %d\n", convert_frame_count);
    av_frame_free(&frame);
    return 0;
}

到此修改完毕
编译测试播放视频延时在500ms左右

编译的so库以及修改的配置文件和代码下载：
https://github.com/itzuo/ijkplayer-android