jikplayer源码线程分析-解封装线程

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前言

提示：jikplayer源码分析目录汇总如下连接：

ijkplayer源码分析汇总

一、解封装重点内容介绍

• 启动解封装线程

1. 主线程中，stream_open中packet_queue_init初始化音视频PacketQueue缓冲区，PacketQueue类似一个链表结构
2. stream_open中frame_queue_init初始化音视频FrameQueue缓冲区，FrameQueue类似一个数组结构
3. stream_open中开启SDL_CreateThreadEx(&is->_video_refresh_tid, video_refresh_thread, ffp, “ff_vout”);视频渲染线程
4. stream_open中开启SDL_CreateThreadEx(&is->_read_tid, read_thread, ffp, “ff_read”);解封装线程

• 运行解封装线程

1. 在解封装线程read_thread中avformat_open_input打开网络流或者本地文件
2. stream_component_open打开音视频流的编解码器，同时打开音视频解码线程
3. av_read_frame，ffmpeg读取音视频流
4. packet_queue_put，将解封装后的音视频数据保存到PacketQueue队列中

解封装线程代码详解：

// ijkplayer/ff_ffplay.c
static int read_thread(void *arg)
{
	// 省略代码 ......

    ic = avformat_alloc_context();
    
	// 省略代码 ......

    if (ffp->skip_calc_frame_rate) {
        av_dict_set_int(&ic->metadata, "skip-calc-frame-rate", ffp->skip_calc_frame_rate, 0);
        av_dict_set_int(&ffp->format_opts, "skip-calc-frame-rate", ffp->skip_calc_frame_rate, 0);
    }

    if (ffp->iformat_name)
        is->iformat = av_find_input_format(ffp->iformat_name);

	// cwy: 打开网络流
    err = avformat_open_input(&ic, is->filename, is->iformat, &ffp->format_opts);
    if (err < 0) {
        print_error(is->filename, err);
        ret = -1;
        goto fail;
    }
    ffp_notify_msg1(ffp, FFP_MSG_OPEN_INPUT);
    
	// 省略代码 ......
	
	
    /* if seeking requested, we execute it */
    if (ffp->start_time != AV_NOPTS_VALUE) {
        int64_t timestamp;

        timestamp = ffp->start_time;
        /* add the stream start time */
        if (ic->start_time != AV_NOPTS_VALUE)
            timestamp += ic->start_time;
        ret = avformat_seek_file(ic, -1, INT64_MIN, timestamp, INT64_MAX, 0);
        if (ret < 0) {
            av_log(NULL, AV_LOG_WARNING, "%s: could not seek to position %0.3f\n",
                    is->filename, (double)timestamp / AV_TIME_BASE);
        }
    }

    is->realtime = is_realtime(ic);

    av_dump_format(ic, 0, is->filename, 0);

    int video_stream_count = 0;
    int h264_stream_count = 0;
    int first_h264_stream = -1;
    for (i = 0; i < ic->nb_streams; i++) {
        AVStream *st = ic->streams[i];
        enum AVMediaType type = st->codecpar->codec_type;
        
        // cwy: 在接收流之前，将所有流都关闭，需要解码哪一路流，在stream_component_open中再将相应的流打开。
        // cwy: 对于多流资源很有用，避免拉取不使用的流，占用带宽
        st->discard = AVDISCARD_ALL;
        if (type >= 0 && ffp->wanted_stream_spec[type] && st_index[type] == -1)
            if (avformat_match_stream_specifier(ic, st, ffp->wanted_stream_spec[type]) > 0)
                st_index[type] = i;

	// 省略代码 ......

    /* open the streams */
    if (st_index[AVMEDIA_TYPE_AUDIO] >= 0) {
    	// cwy: 打开音频流
        stream_component_open(ffp, st_index[AVMEDIA_TYPE_AUDIO]);
    } else {
        ffp->av_sync_type = AV_SYNC_VIDEO_MASTER;
        is->av_sync_type  = ffp->av_sync_type;
    }

    ret = -1;
    if (st_index[AVMEDIA_TYPE_VIDEO] >= 0) {
        ret = stream_component_open(ffp, st_index[AVMEDIA_TYPE_VIDEO]);
    }
    if (is->show_mode == SHOW_MODE_NONE)
        is->show_mode = ret >= 0 ? SHOW_MODE_VIDEO : SHOW_MODE_RDFT;

    if (st_index[AVMEDIA_TYPE_SUBTITLE] >= 0) {
        stream_component_open(ffp, st_index[AVMEDIA_TYPE_SUBTITLE]);
    }
    ffp_notify_msg1(ffp, FFP_MSG_COMPONENT_OPEN);

	// 省略代码 ......

	// cwy: 用于在起始播放之前seek
    /* offset should be seeked*/
    if (ffp->seek_at_start > 0) {
        ffp_seek_to_l(ffp, (long)(ffp->seek_at_start));
    }

	// cwy: 循环读取音视频流
    for (;;) {
        if (is->abort_request)
            break;
#ifdef FFP_MERGE
        if (is->paused != is->last_paused) {
            is->last_paused = is->paused;
            if (is->paused)
                is->read_pause_return = av_read_pause(ic);
            else
                av_read_play(ic);
        }
#endif

		// 省略代码 ......
		
        pkt->flags = 0;
        // cwy: 读取音视频avpacket
        ret = av_read_frame(ic, pkt);
        if (ret < 0) {
            int pb_eof = 0;
            int pb_error = 0;
            if ((ret == AVERROR_EOF || avio_feof(ic->pb)) && !is->eof) {
                ffp_check_buffering_l(ffp);
                pb_eof = 1;
                // check error later
            }
            if (ic->pb && ic->pb->error) {
                pb_eof = 1;
                pb_error = ic->pb->error;
            }
            if (ret == AVERROR_EXIT) {
                pb_eof = 1;
                pb_error = AVERROR_EXIT;
            }

        /* check if packet is in play range specified by user, then queue, otherwise discard */
        stream_start_time = ic->streams[pkt->stream_index]->start_time;
        pkt_ts = pkt->pts == AV_NOPTS_VALUE ? pkt->dts : pkt->pts;
        pkt_in_play_range = ffp->duration == AV_NOPTS_VALUE ||
                (pkt_ts - (stream_start_time != AV_NOPTS_VALUE ? stream_start_time : 0)) *
                av_q2d(ic->streams[pkt->stream_index]->time_base) -
                (double)(ffp->start_time != AV_NOPTS_VALUE ? ffp->start_time : 0) / 1000000
                <= ((double)ffp->duration / 1000000);
        if (pkt->stream_index == is->audio_stream && pkt_in_play_range) {
            packet_queue_put(&is->audioq, pkt);
        } else if (pkt->stream_index == is->video_stream && pkt_in_play_range
                   && !(is->video_st && (is->video_st->disposition & AV_DISPOSITION_ATTACHED_PIC))) {
            // cwy: 保存音视频信息
            packet_queue_put(&is->videoq, pkt);
        } else if (pkt->stream_index == is->subtitle_stream && pkt_in_play_range) {
            packet_queue_put(&is->subtitleq, pkt);
        } else {
            av_packet_unref(pkt);
        }

		// cwy: 这一块代码主要是用于计算点播时缓冲大小，首帧快速开启配置
        if (ffp->packet_buffering) {
            io_tick_counter = SDL_GetTickHR();
            if ((!ffp->first_video_frame_rendered && is->video_st) || (!ffp->first_audio_frame_rendered && is->audio_st)) {
                if (abs((int)(io_tick_counter - prev_io_tick_counter)) > FAST_BUFFERING_CHECK_PER_MILLISECONDS) {
                    prev_io_tick_counter = io_tick_counter;
                    ffp->dcc.current_high_water_mark_in_ms = ffp->dcc.first_high_water_mark_in_ms;
                    ffp_check_buffering_l(ffp);
                }
            } else {
                if (abs((int)(io_tick_counter - prev_io_tick_counter)) > BUFFERING_CHECK_PER_MILLISECONDS) {
                    prev_io_tick_counter = io_tick_counter;
                    ffp_check_buffering_l(ffp);
                }
            }
        }
    }
}