blocks|key|701904|text|“流只有RTP/rtp.pcp.给出的PTS”这是不正常的。这里出了点问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|701905|如果没有dts，这意味着您应该只使用pts。如果确实有B帧，那么dts值将与pts不同。|701906|试试你的代码dts+=+pts，看看会发生什么。|CODE|701907|entityMap^0|1|F|0|0|6|9|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|P|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Q|8|@$9|R|A|S|B|J]]|D|@]|E|$]]|$1|K|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|L|$]]

It is not normal that "The stream has only PTS given by the RTP/RTCP.". Something wrong here. 
If there is no dts, it means you should use pts only. If there are really B frames, then you would have dts values that different than pts.

Try on your code <code>dts = pts</code> and see what happens.

blocks|key|707049|text|我做了几个实验，有些东西要和你分享。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|707050|707051|，无论是否有B帧，mp4+muxer都需要DTS+(至少)：|ordered-list-item|707052|。|707053|-+Monotonically+increasing.
-+DTS+<=+PTS+per+each+frame.
-+PTS+and+DTS+should+start+from+values+close+to+zero+(otherwise+players+like+VLC+has+to+delay+some+time+before+displaying+video).|code-block|syntax|javascript|707054|​|707055|如果流中没有B帧，则|707056|可以从PTS复制DTS并将帧保存到mp4文件中，而不存在任何问题。如果流中有B帧，则情况完全不同。在这种情况下，由于B帧，帧的PTS不会单调增加.因此，仅仅复制DTS+=+PTS肯定是行不通的。我们必须找到一种通过带外发送DTS或从FPS和PTS.|707057|计算DTS的方法。|707058|对于带外发送，这是相当复杂的，因为它需要处理RTSP服务器和RTSP客户机.这里我只想展示从FPS和PTS推导DTS的简单方法。|707059|粗略的步骤如下：|707060|检测帧间的平均持续时间(或FPS)+|offset|length|style|BOLD|707061|707062|从接收RTSP会话的SDP解析FPS。这种方式依赖于RTSP服务器的支持。有的支持，有的不支持。另一种方法是根据帧序列计算帧间的平均持续时间。您可以缓冲等于一个GOP大小的帧数，得到GOP的第一帧和最后一帧的PTS差值除以平均持续时间的帧数。例如，如果假设FPS为30，则计算的平均持续时间应为33,333+us.|unordered-list-item|707063|707064|保存到容器|707065|//+Initialize+container

++++pAVStream->time_base+=+{+1,+AV_TIME_BASE+};+//+PTS/DTS+in+microseconds.
++++pAVFormatCtx->oformat->flags+%7C=+AVFMT_SEEK_TO_PTS;
++++ret+=+avformat_write_header(m_pAVFormatCtx,+&priv_opts);

++++Assume+that+you+have+pre-calculated+average+duration:+
++++nAvgDuration+=+33'333LL;

++++//++Per+each+frame

++++if+(waitingForTheFirstKeyFrame)+{
++++++++if+(!bsKeyFrame)+{
++++++++++++return+false;
++++++++}

++++++++waitingForTheFirstKeyFrame+=+false;
++++++++nPTSOffset+=+nPTS;+//+pts+will+start+from+0
++++++++nStartDTS+=+nPTS+-+nAvgDuration;+//+dts+will+start+from+-nAvgDuration
++++}

++++nDTS+=+nStartDTS;
++++nStartDTS+%2B=+nAvgDuration;+//+dts+is+monotonically+increasing

++++pkt->pts+=+nPTS+-+nPTSOffset;
++++pkt->dts+=+nDTS+-+nPTSOffset;

++++//++Since+PTS/DTS+are+in+microseconds,+no+need+to+rescalling+more.
++++//++Of+course,+you+can+use+a+different+time_base.

++++auto+ret+=+av_interleaved_write_frame(m_pAVFormatCtx,+pkt);|707066|警告：|707067|该解决方案工作良好，假设流的原始PTS+(服务器端)单调增加，帧间没有间隙，没有帧丢失。否则，可能会降低DTS的准确性，甚至无法播放mp4文件。|707068|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|I|0|0|0|0|0|5|0|0|0|3|0|0^^$0|@$1|2|3|4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|1M|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|1N|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|1O|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1P|8|@]|9|@]|A|$]]|$1|Q|3|R|5|E|7|1Q|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1R|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1S|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1T|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1U|8|@$10|1V|11|1W|12|13]]|9|@]|A|$]]|$1|14|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]|$1|15|3|16|5|17|7|1Y|8|@]|9|@]|A|$]]|$1|18|3|G|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|20|8|@$10|21|11|22|12|13]]|9|@]|A|$]]|$1|1B|3|1C|5|J|7|23|8|@]|9|@]|A|$K|L]]|$1|1D|3|1E|5|6|7|24|8|@$10|25|11|26|12|13]]|9|@]|A|$]]|$1|1F|3|1G|5|6|7|27|8|@]|9|@]|A|$]]|$1|1H|3|-4|5|6|7|28|8|@]|9|@]|A|$]]]|1I|$]]

I have done several experiments and have some things to share to you.

<ol>
<li>Regardless having B-frames or not, mp4 muxer requires DTS must be (at least): 

<ul>
<li>Monotonically increasing.</li>
<li>DTS &lt;= PTS per each frame.</li>
<li>PTS and DTS should start from values close to zero (otherwise players like VLC has to delay some time before displaying video).</li>
</ul></li>
<li>If there is no B-frames in the stream, DTS could be copied from PTS and saving frames to
a mp4 file without any issue.</li>
<li>If there are B-frames in the stream, the story is total different.
In this case, PTS of frames are not monotonically increased due to B-frames.
Hence, just copying DTS = PTS definitely won't work. We have to find a way to 
have DTS by either sending DTS via out-of-band or calculating from FPS and PTS.</li>
</ol>

For sending out-of-band, it is quite complicated because it requires handling both
RTSP server and RTSP client. Here I just want to show the simple way of deducing DTS from FPS and PTS.

Rough steps are like this:

Detects average duration (or FPS) between frames

<ul>
<li>Parses FPS from SDP of receiving RTSP session. This way depends on
support of RTSP server. Some support, others do not.  </li>
<li>Another way is to calculate average duration between frames from sequence of
frames. You can buffer number of frames equal to size of one GOP,
getting the PTS difference of the first and the last frame of the GOP
divided by the number of frames you will have the average duration.
Example, if the FPS is assumed 30, then calculated average duration
should be approx 33,333 us.</li>
</ul>

Saving to the container

<pre><code>// Initialize container

 pAVStream-&gt;time_base = { 1, AV_TIME_BASE }; // PTS/DTS in microseconds.
 pAVFormatCtx-&gt;oformat-&gt;flags |= AVFMT_SEEK_TO_PTS;
 ret = avformat_write_header(m_pAVFormatCtx, &amp;priv_opts);

 Assume that you have pre-calculated average duration: 
 nAvgDuration = 33'333LL;

 // Per each frame

 if (waitingForTheFirstKeyFrame) {
 if (!bsKeyFrame) {
 return false;
 }

 waitingForTheFirstKeyFrame = false;
 nPTSOffset = nPTS; // pts will start from 0
 nStartDTS = nPTS - nAvgDuration; // dts will start from -nAvgDuration
 }

 nDTS = nStartDTS;
 nStartDTS += nAvgDuration; // dts is monotonically increasing

 pkt-&gt;pts = nPTS - nPTSOffset;
 pkt-&gt;dts = nDTS - nPTSOffset;

 // Since PTS/DTS are in microseconds, no need to rescalling more.
 // Of course, you can use a different time_base.

 auto ret = av_interleaved_write_frame(m_pAVFormatCtx, pkt);
</code></pre>

Caution: 

This solution works well with an assumption that the original PTS of the stream (at server side) are monotonically increased, there are no gaps between frames and there is no frame loss. Otherwise, the accuracy of DTS may be reduced or even the mp4 file could not be played.

I want to save a h264 video stream received from a RTSP source to a MP4 container.
Not like other questions asked on SO, here the challenges I face are: 

<ul>
<li>The stream contains B frames. </li>
<li>The stream has only PTS given by the RTP/RTCP.</li>
</ul>

Here is the code I did

<pre><code>// ffmpeg
 pkt-&gt;data = ..;
 pkt-&gt;size = ..;
 pkt-&gt;flags = bKeyFrame? AV_PKT_FLAG_KEY : 0; 
 pkt-&gt;dts = AV_NOPTS_VALUE;
 pkt-&gt;pts = PTS;

 // PTS is based on epoch microseconds so I ignored re-scaling.
 //av_packet_rescale_ts(pkt, { 1, AV_TIME_BASE }, muxTimebase);

 auto ret = av_interleaved_write_frame(m_pAVFormatCtx, pkt);
</code></pre>

I received a lot of error messages like this: 
 "Application provided invalid, non monotonically increasing dts to muxer ...".

Result: the mp4 file is playable via VLC but the FPS is just a half of the original FPS and the video duration is incorrect (VLC shows a weird number).

So how do I set correct DTS and PTS before sending to the container?

Update:
I have tried some changes, though not successfully yet, I found that the reason of the frame rate drop is due to the muxer discards frames having incorrect DTS.
Additionally, if I set start of PTS and DTS value too big, some players like VLC has to delay some time before showing video.

How to write a video stream containing B-frame and no DTS to a MP4 container?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我希望将从RTSP源接收到的h264视频流保存到MP4容器中。与其他问题不同，我所面临的挑战是：流包含B帧。流只有RTP/rtcp.rtcp.提供的PTS。这是我做过的代码//  ffmpeg    pkt->data = ..;    pkt->size = ..;    pkt->flags = bKeyFrame...

问如何将包含B帧和没有DTS的视频流写入MP4容器？
EN

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问如何将包含B帧和没有DTS的视频流写入MP4容器？EN