ffmpeg关于dts和pts收集

淩亂°似流年 2022-10-12 05:48 174阅读 0赞

深入理解pts，dts，time\_base  
http://blog.chinaunix.net/uid-20554957-id-5836134.html

视音频pts计算  
https://blog.csdn.net/dancing\_night/article/details/45972361

关于FFmpeg的pts转时基时的计算步骤(包括无输入流地址和有输入流地址)  
https://blog.csdn.net/weixin\_44517656/article/details/110559611  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzM2MDcwNw_size_16_color_FFFFFF_t_70]这里对第一步说明：  
cal\_duration是1000000/25，ffmpeg中的时间基是1.0*10-6 其实就是微妙，这里cal\_duration就是1s占多少微妙，这样做好处就是没有s的小数了。  
pts的计算可以转化一下 （n*cal\_duration）/ 10000，这就是有转换成秒了，然后再乘以输入时间基，就成了按照输入基准计算出来的pts，这样就有了第三步转时基的操作。  
关于时间基一般来说flv mp4等都是1000就是毫秒，摄像头采集90kHZ,ffmpeg1000000.

FFmpeg中的时间基(time\_base), AV\_TIME\_BASE  
https://www.cnblogs.com/yongdaimi/p/10684953.html

ffmpeg中tbr tbc tbn的含义解释  
https://blog.csdn.net/xujaiwei/article/details/77773438

ffmpeg time\_base  
http://www.cnitblog.com/luofuchong/archive/2014/11/28/89869.html

拓展：时间基为什么是90KhZ？  
the following sections describe the video encodings that are defined  
in this memo and give their abbreviated names used for  
identification. These video encodings and their payload types are  
listed in Table 5.

All of these video encodings use an RTP timestamp frequency of 90,000  
Hz, the same as the MPEG presentation time stamp frequency. This  
frequency yields exact integer timestamp increments for the typical  
24 (HDTV), 25 (PAL), and 29.97 (NTSC) and 30 Hz (HDTV) frame rates  
and 50, 59.94 and 60 Hz field rates. While 90 kHz is the **RECOMMENDED**  
rate for future video encodings used within this profile, other rates  
MAY be used. However, it is not sufficient to use the video frame  
rate (typically between 15 and 30 Hz) because that does not provide  
adequate resolution for typical synchronization requirements when  
calculating the RTP timestamp corresponding to the NTP timestamp in  
an RTCP SR packet. The timestamp resolution MUST also be sufficient  
for the jitter estimate contained in the receiver reports.

For most of these video encodings, the RTP timestamp encodes the  
sampling instant of the video image contained in the RTP data packet.  
If a video image occupies more than one packet, the timestamp is the  
same on all of those packets. Packets from different video images  
are distinguished by their different timestamps.

Most of these video encodings also specify that the marker bit of the  
RTP header SHOULD be set to one in the last packet of a video frame  
and otherwise set to zero. Thus, it is not necessary to wait for a  
following packet with a different timestamp to detect that a new  
frame should be displayed

比如：fps为25和30  
1/25=x/90K  
1/30=x/90k  
这样都能整除，90k就是

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzM2MDcwNw_size_16_color_FFFFFF_t_70]: /images/20221005/6ebc139f8d2846db9378a339beefdaee.png