当前位置：网站首页>音视频录入的pts和dts问题
音视频录入的pts和dts问题
2022-08-09 13:05:00 【zhouyongku】
目前我在从事远程rtsp视频采集+本地录音整合到一个mp4文件的工作，遇到的问题：由于视频的编解码以及网络耗时导致音视频无法同步，播放出来的画面延迟很严重。
为了解决这个问题，研究了一下音视频pts和dts。
录像音视频的原理：
(1) 获取网络码流-->抛弃异常包--->等待关键帧(为了图像不花图)----->开始转封装视频数据------>更改pts和dts------>av_write_frame
(2)设置音频回调函数(音频采集回调的条件为满足采样一个音频帧则返回)本地音频采集回调------>回调的数据----->编码音频 ---->更改Pts和dts---->av_write_frame
备注1： 音频帧：规定1024个采样点为一帧 如果采样位数为16bit 左右声道均采集 则采样一个音频回调需要1024*16/2*2=4096bytes
备注2：抛弃异常包：由于刚开始获取到的几个视频包的pts和dts是异常跳变而非递增的，所以需要等到视频包连续递增跳变的时候才能使用
并且为了保存的录像解码不花图，则需要第一帧写入的包为key包
BOOL CRecordRtspAndMicrophone::GetStreamPacket( AVPacket *pkt)
{
BOOL bRet = FALSE;
//如果暂停录像等情况会释放rtsp链接 所以需要对指针保护
if (NULL != m_pRtspFmt)
{
if (av_read_frame(m_pRtspFmt, pkt) == 0)
{
if (m_bFirstFrm)
{
m_bFirstFrm = FALSE;
m_nFirstPts = pkt->pts;
m_nFirstDts = pkt->dts;
}
//如果是视频刚开始段--刚开始链接、重新连接、创建新文件等情况需要等待关键帧
if (m_bFirstKeyFrm)
{
if (MAX_VIDEO_FIRST_WAIT_FRM_CNT <= m_nWaitFrmCnt++)
{
if(pkt->pts > m_nFirstPts)
{
if (pkt->flags == AV_PKT_FLAG_KEY)
{
m_bFirstKeyFrm = FALSE;
m_nFirstKeyPts = pkt->pts;
m_nFirstKeyDts = pkt->dts;
bRet = TRUE;
}
}
}
}
//普通情况只要读取到包裹就可以返回TRUE
else
{
//pkt->pts -= m_nFirstPts;
//pkt->dts -= m_nFirstDts;
bRet = TRUE;
}
}
}
return bRet;
}pts:显示时间戳
dts:解码时间戳
一、视频时间戳转换
av_rescale_q_rnd函数 将时间戳从一个进制转换到另外一个进制
系统默认的H264的time_base= num=1/den=90000 mp4文件的time_base= num=1/den=12800 flv文件的time_base=num=1/den=1000
可以看出来 转换后的数据为 m=12800/90000*m 不能直接调用乘法计算 会导致溢出为负数
m_pInVst----输入的视频stream 类型为AVStream* =【AVFormatContext-> AVStream **streams[视频index]】
//分析读入的流 读取其音频和视频下标
for (int i = 0; i<m_pRtspFmt->nb_streams; i++)
{
if (m_pRtspFmt->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
m_pInVst = m_pRtspFmt->streams[i];
m_nInViStreamIdx = i;
LOG(LOG_RTM, "[ERROR]find video stream index=%d",i);
}
else if (m_pRtspFmt->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
{
m_pInAst = m_pRtspFmt->streams[i];
m_nInAuStreamIdx = i;
LOG(LOG_RTM, "[ERROR]find audio stream index=%d", i);
}
}m_pOutVst---输出的视频stream
BOOL CRecordRtspAndMicrophone::AddVideoOutput()
{
m_nOutViStreamIdx = 0;
m_pOutVst = avformat_new_stream( m_pMp4Fmt, m_pInVst->codec->codec);
avcodec_copy_context(m_pOutVst->codec, m_pInVst->codec);
//m_pOutVst->sample_aspect_ratio = m_pInVst->codec->sample_aspect_ratio;
m_nImgW = m_pInVst->codec->width;
m_nImgH = m_pInVst->codec->height;
copy_video_stream_info(m_pOutVst, m_pInVst, m_pMp4Fmt);
if (m_pMp4Fmt->oformat->flags & AVFMT_GLOBALHEADER)
m_pOutVst->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
LOG(LOG_RTM, "AddVideoOutput");
return TRUE;
}这个函数是收到一个视频数据包 并将原来的时间戳转换为输出mp4文件的时间戳
BOOL CRecordRtspAndMicrophone::WriteVideoFrame( AVPacket *pPkt )
{
pPkt->stream_index = m_nOutViStreamIdx;
pPkt->pts -= m_nFirstKeyPts;
pPkt->dts -= m_nFirstKeyDts;
pPkt->pts = av_rescale_q_rnd(pPkt->pts, m_pInVst->time_base, m_pOutVst->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
pPkt->dts = av_rescale_q_rnd(pPkt->dts, m_pInVst->time_base, m_pOutVst->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
pPkt->duration = av_rescale_q(pPkt->duration, m_pInVst->time_base, m_pOutVst->time_base);
pPkt->pos = -1;
m_player.InputStream(pPkt, VIDEO_STREAM);
if (av_write_frame(m_pMp4Fmt, pPkt))
{
LOG(LOG_ERROR,"[ERROR] writing video frame,fmt=0x%x,audiostream=0x%x,videostream=0x%x,pktsize=%d", m_pMp4Fmt,m_pOutAst,m_pOutVst, pPkt->size);
}
else
{
LOG(LOG_DEBUG, "[Record] videoout packet type=%d\tlen=%d,pts=%d,dts=%d,pb=%d",
pPkt->stream_index, pPkt->size, (int)pPkt->pts, (int)pPkt->dts, (int)m_pMp4Fmt->pb->pos);
}
m_nVideoPts = pPkt->pts;
return TRUE;
}二、音频时间戳的处理(时间延迟和时间戳构造)
1、用本地获取到的pcm数据进行编码
AVPacket pkt;
av_new_packet(&pkt, m_nAudioFrmSize);
memcpy(m_pAFrame->data[0], m_AudioCircleBuf.ele[nPos].data, m_nAudioFrmSize);
m_nAudioTotalSize += m_nAudioFrmSize;
if (m_AudioCircleBuf.ele[nPos].nMaxLen < m_nAudioFrmSize)
{
LOG(LOG_ERROR, "[ERROR]音频编码所需内存异常!");
}
if (avcodec_encode_audio2(m_pOutAst->codec, &pkt, m_pAFrame, &got_frame) != 0)
{
LOG(LOG_ERROR, "[ERROR]音频编码失败!");
}音频采样bufsize的设置为:通道数*采样bit/8*1024
m_nAudioFrmSize = av_samples_get_buffer_size(NULL, pCodecCtx->channels, pCodecCtx->frame_size, pCodecCtx->sample_fmt, 1);2、对编码后的时间戳进行构造
(1)我设置的每次音频缓冲区满了就回调--而我的缓冲区为4096字节(16bit*双通道*1024/帧) 所以我每次收到的音频pcm数据实际上为一帧！
则我的
pts可以设置为---------------1024*帧数
dts=pts
反推一下 Pts可以泛化：pts=dts=音频size/通道数/(bit/8)/1024
(2)音频延迟
如果要延迟m_nAudioTimeDelayMs=500毫秒保持与网络同步 则可以设置pts=dts+延迟时间dms
如果采样率为AUDIO_SAMP_RATE=22050 双通道 16bit 则dms=22050*500/1000
BOOL CRecordRtspAndMicrophone::WriteDeviceAudio()
{
//return TRUE;
if (NULL == m_pOutAst) return FALSE;
UINT nPos = 0;
DWORD dwTimeStamp = GetTickCount();
BOOL bRet = FALSE,ret=0;
AVPacket pkt;
int got_frame = 0, nRet;
Lock();
if (m_AudioCircleBuf.nItemCnt)
{
nPos = (m_AudioCircleBuf.nRead + 1) % CIRCLE_BUF_LEN;
LOG(LOG_DEBUG, "[GetAudio] buf itemcnt=%d,read=%d,write=%d,time=%u",
m_AudioCircleBuf.nItemCnt, m_AudioCircleBuf.nRead,
m_AudioCircleBuf.nWrite, m_AudioCircleBuf.ele[nPos].dwTimeStamp);
av_new_packet(&pkt, m_nAudioFrmSize);
memcpy(m_pAFrame->data[0], m_AudioCircleBuf.ele[nPos].data, m_nAudioFrmSize);
m_nAudioTotalSize += m_nAudioFrmSize;
if (m_AudioCircleBuf.ele[nPos].nMaxLen < m_nAudioFrmSize)
{
LOG(LOG_ERROR, "[ERROR]音频编码所需内存异常!");
}
if (avcodec_encode_audio2(m_pOutAst->codec, &pkt, m_pAFrame, &got_frame) != 0)
{
LOG(LOG_ERROR, "[ERROR]音频编码失败!");
}
else
{
pkt.pts = audio_frame_cnt * 1024;
pkt.pts += m_nAudioTimeDelayMs * AUDIO_SAMP_RATE / 1024;
pkt.flags |= AV_PKT_FLAG_KEY;
pkt.stream_index = m_nOutAuStreamIdx;
audio_frame_cnt++;
pkt.dts = audio_frame_cnt*1024;
m_nAudioPts = pkt.pts;
m_Fms.InputStream(&pkt, AUDIO_STREAM);
/* write the compressed frame in the media file */
if (ret = av_write_frame(m_pMp4Fmt, &pkt), ret < 0)
{
LOG(LOG_ERROR, "[ERROR]Error while writing audio frame,fmt=0x%x,audiostream=0x%x,videostream=0x%x,pktsize=%d", m_pMp4Fmt, m_pOutAst, m_pOutVst, pkt.size);
}
else
{
LOG(LOG_DEBUG, "[Record] packet type=%d\tlen=%d,pts=%d,dts=%d,pb=%d",
pkt.stream_index, pkt.size, (int)pkt.pts, (int)pkt.dts, (int)m_pMp4Fmt->pb->pos);
bRet = TRUE;
}
}
av_free_packet(&pkt);
m_AudioCircleBuf.nRead = nPos;
m_AudioCircleBuf.nItemCnt--;
}
UnLock();
return bRet;
}三、写入的pts和dts分析
1、视频时间戳
Line 11: 2014-08-12 10:52:46:011 [Record] videoout packet type=0 len=12911,pts=1535,dts=1535,pb=37327
Line 16: 2014-08-12 10:52:46:037 [Record] videoout packet type=0 len=12504,pts=2048,dts=2048,pb=50343
Line 21: 2014-08-12 10:52:46:079 [Record] videoout packet type=0 len=13178,pts=2559,dts=2559,pb=64033
Line 26: 2014-08-12 10:52:46:121 [Record] videoout packet type=0 len=12976,pts=3072,dts=3072,pb=77521
Line 28: 2014-08-12 10:52:46:162 [Record] videoout packet type=0 len=14037,pts=3583,dts=3583,pb=91558
Line 33: 2014-08-12 10:52:46:208 [Record] videoout packet type=0 len=13122,pts=4095,dts=4095,pb=105192
Line 38: 2014-08-12 10:52:46:252 [Record] videoout packet type=0 len=12531,pts=4609,dts=4609,pb=118235
Line 43: 2014-08-12 10:52:46:296 [Record] videoout packet type=0 len=11679,pts=5119,dts=5119,pb=130426
Line 48: 2014-08-12 10:52:46:319 [Record] videoout packet type=0 len=11535,pts=5632,dts=5632,pb=142473
Line 53: 2014-08-12 10:52:46:362 [Record] videoout packet type=0 len=11031,pts=6144,dts=6144,pb=154016
Line 55: 2014-08-12 10:52:46:404 [Record] videoout packet type=0 len=11451,pts=6655,dts=6655,pb=165467
Line 60: 2014-08-12 10:52:46:449 [Record] videoout packet type=0 len=10687,pts=7167,dts=7167,pb=176666
Line 65: 2014-08-12 10:52:46:491 [Record] videoout packet type=0 len=9677,pts=7680,dts=7680,pb=186855
Line 70: 2014-08-12 10:52:46:535 [Record] videoout packet type=0 len=8871,pts=8191,dts=8191,pb=196238
Line 75: 2014-08-12 10:52:46:558 [Record] videoout packet type=0 len=9140,pts=8703,dts=8703,pb=205890
Line 80: 2014-08-12 10:52:46:600 [Record] videoout packet type=0 len=10013,pts=9216,dts=9216,pb=216415
Line 82: 2014-08-12 10:52:46:642 [Record] videoout packet type=0 len=9973,pts=9727,dts=9727,pb=226388
Line 87: 2014-08-12 10:52:46:686 [Record] videoout packet type=0 len=9924,pts=10239,dts=10239,pb=236824
Line 92: 2014-08-12 10:52:46:730 [Record] videoout packet type=0 len=10096,pts=10751,dts=10751,pb=247432
Line 97: 2014-08-12 10:52:46:773 [Record] videoout packet type=0 len=11293,pts=11263,dts=11263,pb=259237
Line 102: 2014-08-12 10:52:46:797 [Record] videoout packet type=0 len=11598,pts=11775,dts=11775,pb=271347
Line 107: 2014-08-12 10:52:46:840 [Record] videoout packet type=0 len=12024,pts=12287,dts=12287,pb=283883
Line 109: 2014-08-12 10:52:46:882 [Record] videoout packet type=0 len=11264,pts=12799,dts=12799,pb=295147
Line 114: 2014-08-12 10:52:46:927 [Record] videoout packet type=0 len=11842,pts=13311,dts=13311,pb=307501
Line 119: 2014-08-12 10:52:46:971 [Record] videoout packet type=0 len=11135,pts=13823,dts=13823,pb=319148共写了25条数据--与海康每个nual一个帧的策略匹配--帧率为25 pts从1535递增到13823=12288~=12800 可以看出来 视频时间戳无问题 长时间统计后每秒的pts和dts增加绝对为12800 这样我就可以确定我的pts设置没有任何问题
2、音频时间戳
Line 15: 2014-08-12 10:52:46:036 [Record] packet type=1 len=512,pts=10766,dts=1024,pb=37839
Line 20: 2014-08-12 10:52:46:078 [Record] packet type=1 len=512,pts=11790,dts=2048,pb=50855
Line 25: 2014-08-12 10:52:46:120 [Record] packet type=1 len=512,pts=12814,dts=3072,pb=64545
Line 32: 2014-08-12 10:52:46:208 [Record] packet type=1 len=512,pts=13838,dts=4096,pb=92070
Line 37: 2014-08-12 10:52:46:252 [Record] packet type=1 len=512,pts=14862,dts=5120,pb=105704
Line 42: 2014-08-12 10:52:46:296 [Record] packet type=1 len=512,pts=15886,dts=6144,pb=118747
Line 47: 2014-08-12 10:52:46:319 [Record] packet type=1 len=512,pts=16910,dts=7168,pb=130938
Line 52: 2014-08-12 10:52:46:361 [Record] packet type=1 len=512,pts=17934,dts=8192,pb=142985
Line 59: 2014-08-12 10:52:46:449 [Record] packet type=1 len=512,pts=18958,dts=9216,pb=165979
Line 64: 2014-08-12 10:52:46:491 [Record] packet type=1 len=512,pts=19982,dts=10240,pb=177178
Line 69: 2014-08-12 10:52:46:534 [Record] packet type=1 len=512,pts=21006,dts=11264,pb=187367
Line 74: 2014-08-12 10:52:46:558 [Record] packet type=1 len=512,pts=22030,dts=12288,pb=196750
Line 79: 2014-08-12 10:52:46:600 [Record] packet type=1 len=512,pts=23054,dts=13312,pb=206402
Line 86: 2014-08-12 10:52:46:685 [Record] packet type=1 len=512,pts=24078,dts=14336,pb=226900
Line 91: 2014-08-12 10:52:46:729 [Record] packet type=1 len=512,pts=25102,dts=15360,pb=237336
Line 96: 2014-08-12 10:52:46:773 [Record] packet type=1 len=512,pts=26126,dts=16384,pb=247944
Line 101: 2014-08-12 10:52:46:796 [Record] packet type=1 len=512,pts=27150,dts=17408,pb=259749
Line 106: 2014-08-12 10:52:46:839 [Record] packet type=1 len=512,pts=28174,dts=18432,pb=271859
Line 113: 2014-08-12 10:52:46:927 [Record] packet type=1 len=512,pts=29198,dts=19456,pb=295659
Line 118: 2014-08-12 10:52:46:970 [Record] packet type=1 len=512,pts=30222,dts=20480,pb=308013
共写了21条数据--与我设置的音频采样率22050保持一致
音频每秒次采样帧数为22050/1024(点/帧)=21.53
pts从10766递增到30222==差值为20000~=22050 则表明我的pts设置没有问题 长期统计下来每秒的差值肯定为22050
四、总结
音视频的pts和dts设置需要满足与每秒采样点数的对应关系：每秒Pts和dts的增加需要=采样点
音频一帧为1024个点
如果要快进或者慢放 则将pts增加或者减少
边栏推荐
- glibc 内存管理模型 释放 C库内存缓存
- NC15 求二叉树的层序遍历
- JS轮播图实现
- 5G China unicom 一般性异常处理
- ArcEngine(九)图形绘制
- 周末看点回顾|我国IPv6网络全面建成；2022昇腾AI开发者创享日·南京站成功举办…
- 陈强教授《机器学习及R应用》课程 第十六章作业
- Anta and Huawei Sports Health jointly verify the champion running shoes and lead Chinese sports with innovation
- R 语言 2010.1至2021.12艾滋病每月发病人数 时间序列分析
- Microsoft 10/11 命令行打开系统设置页（WUAP，!WIN32）
猜你喜欢
Come and throw eggs.
FFmpeg multimedia file processing (implementation of ffmpeg operation directory and list)
Map mixed density function and quantile added line
npm install失败
蓝桥历届真题-既约分数
FFmpeg multimedia file processing (the basic concept of ffmpeg processing stream data)
乐东消防救援大队应邀为干部开展消防安全培训
面试攻略系列（四）-- 你不知道的大厂面试
Unicom network management protocol block diagram
联通网管协议框图
随机推荐
FFmpeg multimedia file processing (the basic concept of ffmpeg processing stream data)
Oracle Recovery Tools修复空闲坏块
[FPGA Tutorial Case 48] Image Case 8 - Realization of Converting RGB Image to HSV Image Based on FPGA, Assisted Verification by MATLAB
handwritten big pile
Uni - app - uview Swiper shuffling figure component, click on the links to jump (click to get the item after the row data, remove data operation)
Professor Chen Qiang's "Machine Learning and R Application" course Chapter 13 Assignment
ARM板卡增加路由功能
Unicom network management protocol block diagram
ArcEngine(九)图形绘制
周末看点回顾|我国IPv6网络全面建成；2022昇腾AI开发者创享日·南京站成功举办…
Final assignment of R language data analysis in a university
An Offer 21. Adjust the array in order to make odd in even the front (loop invariant)
render解析
现在40系显卡都快出来了，为何1060型号的显卡还有这么多人用？
WSA toolkit installed app store tip doesn't work how to solve?
How to solve the 0x80070005 error when the computer is reinstalled and the system is restored
NFS pays special attention to the problem of permissions
gin的中间件和路由分组
ArcEngine(十)创建矢量图层
Bitmaps and bit operations