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一分钟快速搭建 rtmpd 服务器: https://blog.csdn.net/freeabc/article/details/102880984

软件下载地址: http://www.qiyicc.com/download/rtmpd.zip

github 地址：https://github.com/superconvert/smart_rtmpd

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为什么 RTP 的视频的采样率是 90kHz ?

其实我原来一直也有这个疑问，网上也有些解释，感觉有点太牵强，不完善。今天我就来和大家说一说这个的来历。

那怎么样才更具有说服力呢？当然是引经据典，参看我们的 RFC 了。

其中 rfc3551 中，第 5 小节，是这么介绍的。

5.  Video

   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.

   从上文我们可以看到 90 kHz 等同于 MPEG 呈现时间戳频率。同时 90 kHz 满足
   多种制式以及频段时间戳增长为整数的需要，目的就是减少时间戳偏差。同时 90 kHz
   也满足 RTCP SR 计算 NTP 同步的需要，也满足接收报告中 jitter 的估算。
   简而言之一句话：90 kHz 就是 RTP 视频时间戳的天选之子！