player stop处理

几乎所有的播放器都是基于ffmpeg,所以这就用ffmpeg 来说吧.

大家都只是stop其实做了几个处理,一个是暂停播放,另外一个就是将播放位置seek到0点上.

除了这些，其实内部在seek的时候将播放队列的buffer 全部都清空了.

为了不纸上谈兵，这里就贴一段ffplay的代码

 if (is->seek_req) {
            int64_t seek_target= is->seek_pos;
            int64_t seek_min= is->seek_rel > 0 ? seek_target - is->seek_rel + 2: INT64_MIN;
            int64_t seek_max= is->seek_rel < 0 ? seek_target - is->seek_rel - 2: INT64_MAX;
//FIXME the +-2 is due to rounding being not done in the correct direction in generation
//      of the seek_pos/seek_rel variables

            ret = avformat_seek_file(is->ic, -1, seek_min, seek_target, seek_max, is->seek_flags);
            if (ret < 0) {
                fprintf(stderr, "%s: error while seeking\n", is->ic->filename);
            }else{
                if (is->audio_stream >= 0) {
                    packet_queue_flush(&is->audioq);
                    packet_queue_put(&is->audioq, &flush_pkt);
                }
                if (is->subtitle_stream >= 0) {
                    packet_queue_flush(&is->subtitleq);
                    packet_queue_put(&is->subtitleq, &flush_pkt);
                }
                if (is->video_stream >= 0) {
                    packet_queue_flush(&is->videoq);
                    packet_queue_put(&is->videoq, &flush_pkt);
                }
            }
            is->seek_req = 0;
            eof= 0;
        }

seek完之后调用flush把缓冲队列的所有内容清空，包括音频，视频，字幕等数据.