ffmpeg简单多线程播放器

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ffmpeg简单多线程播放器

2023-03-24 22:40| 来源: 网络整理| 查看: 265

音视频同步-主要代码逻辑也就是你追我敢的过程

因为音频格式sample channel rate 都是固定的所以某一段音频时间是可以确定的，所以一音频为基准视频同步到音频

常规做法：展示一帧视频帧后，得到下一帧视频帧的PTS, 和当前音频的时钟锁一个比较，如果在之前那就立即播放，如果在之后那就设置一个delay ,然后设置进定时器，当定时器超时后，刷新新的视频帧。

av_frame_get_best_effort_timestamp(pFrame)) 可以直接获得一个对应AvFrame 中获得一个合适pts pts转成秒需要乘以time_base 然后对pts做一定计算如果可以用就直接 is->video_clock = pts 就行音视频同步主要具体代码逻辑

在主要结构体里面增加5个参数 audio_clock 当前音频帧时间 video_clock 当前视频帧的下一帧的时间 frame_timer 下次要回调的timer frame_last_pts 视频上一帧的pts frame_last_delay 上一帧视频播放的delay

double audio_clock; double video_clock; ///pts - is->frame_last_pts

2判断delay 并且代替前一步

delay = vp->pts - is->frame_last_pts; /* the pts from last time */ if(delay = 1.0) { delay = is->frame_last_delay; } is->frame_last_delay = delay; is->frame_last_pts = vp->pts;

3 获得当前音频帧的PTS 和正在播放帧的下一帧（也就是当前处理帧）计算他们之间的diff

ref_clock = get_audio_clock(is); diff = vp->pts - ref_clock;

4 sync_threshold 不能让帧小于音频的最小帧率 if(fabs(diff) < AV_NOSYNC_THRESHOLD) 如果前面得到的距离满足最小帧处理要求那就同步处理如果diff = sync_threshold 说明距离播放还有一段时间吧delay 增长

sync_threshold = (delay > AV_SYNC_THRESHOLD) ? delay : AV_SYNC_THRESHOLD; if(fabs(diff) < AV_NOSYNC_THRESHOLD) { if(diff = sync_threshold) { delay = 2 * delay; }

5 在当前回调时间基础上加上上面计划好的delay时间

is->frame_timer += delay;

6 计算实际时间中的delay 保证最小值不低于音频帧的帧率最后传入实际需要时间去刷新视频渲染 +0.5是加一个偏执

actual_delay = is->frame_timer - (av_gettime() / 1000000.0); if(actual_delay < 0.010) { /* Really it should skip the picture instead */ actual_delay = 0.010; } schedule_refresh(is, (int)(actual_delay * 1000 + 0.5)); void video_refresh_timer(void *userdata) { VideoState *is = (VideoState *)userdata; VideoPicture *vp; double actual_delay, delay, sync_threshold, ref_clock, diff; if(is->video_st) { if(is->pictq_size == 0) { schedule_refresh(is, 1); } else { vp = &is->pictq[is->pictq_rindex]; delay = vp->pts - is->frame_last_pts; /* the pts from last time */ if(delay = 1.0) { /* if incorrect delay, use previous one */ delay = is->frame_last_delay; } /* save for next time */ is->frame_last_delay = delay; is->frame_last_pts = vp->pts; /* update delay to sync to audio */ ref_clock = get_audio_clock(is); diff = vp->pts - ref_clock; /* Skip or repeat the frame. Take delay into account FFPlay still doesn't "know if this is the best guess." */ sync_threshold = (delay > AV_SYNC_THRESHOLD) ? delay : AV_SYNC_THRESHOLD; if(fabs(diff) delay = 0; } else if(diff >= sync_threshold) { delay = 2 * delay; } } is->frame_timer += delay; /* computer the REAL delay */ actual_delay = is->frame_timer - (av_gettime() / 1000000.0); if(actual_delay is->pictq_rindex = 0; } SDL_LockMutex(is->pictq_mutex); is->pictq_size--; SDL_CondSignal(is->pictq_cond); SDL_UnlockMutex(is->pictq_mutex); } } else { schedule_refresh(is, 100); } }

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ffmpeg简单多线程播放器

ffmpeg简单多线程播放器

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