关于 H264 中的系统数据速率
我有一个引擎来检查 H264 视频是否符合 AVCHD 或 BDMV 规范，规范提到 MAX 系统数据速率高达 24 Mbit/s，我想知道如何计算系统数据速率？ 它是否意味着整个文件的平均值？ 还是说1秒的平均值？
I have a engine to check the H264 video is compliance with AVCHD or BDMV spec, the SPEC mentions the MAX system data rate is up to 24 Mbit/s, I want to know how to calculate the system data rate? Does it mean the average of whole file? Or does it mean the average of 1 second?
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该最大值指定您永远不会超过 24Mbps，因此您在任何 42nS（大约）周期内永远不会发送超过一位。 您可以通过简单的乘法将其扩展到您想要的任何时间范围，直到您在一秒钟内永远不会突发超过 24M 位（并且您仍然不会在构成该秒的任何 24M 42nS 周期中发送超过一位） ）。
当您计算任何时间段的平均值时，它必须低于指定的最大突发，但仅被视为平均值。 我们从事 CATV 行业的人花费了大量时间试图使传输系统表现得好像平均速率是恒定速率，因为如果您有一定的视频吞吐量（以比特为单位），您就不想浪费其中任何一个。 我们对视频进行“速率整形”，并在接收信号的数字机顶盒中使用自适应缓冲。
美国宽带有线系统上的单个 QAM256 通道将支持 40Mbps，通常支持 10 到 12 个标准清晰度信号，平均比特率约为 4Mbps。 当图像中存在大量不可预测的变化时，这些通道将突发至 9Mbps。 正如您可以想象的那样，一场拳击比赛（有很多动作）比在办公桌上阅读的网络新闻主播需要更多的带宽，因此我们还尝试匹配频道来填充可用带宽。
通常，我们只能在同一个 40Mbps 频道中容纳 3 个高清频道，这些频道的平均比特率约为 12.5Mbps，正如您上面提到的，比特率仅限于 24Mbps。
希望这可以帮助！
The maximum specifies that you that you will never exceed 24Mbps so you will never send more than one bit in any 42nS (approximately) period. You can scale that to any time frame you want by simple multiplication to the point when you will never burst beyond 24M bits in one second (and you will still never send more than one bit in any of the 24M 42nS periods that make up that second).
When you calculate an average for any time period, it MUST be below the specified maximum burst, but is simply considered an average. Those of us in the CATV industry spend a lot of time trying to make the transmission system behave as if the average rate is a constant rate, because if you have a certain throughput (in bits) for video, you don't want to waste any of it. We "rate shape" the video as well as using adaptive buffering in the digital set-top boxes that receive the signal.
A single QAM256 channel on the U.S. broadband cable system will support 40Mbps and usually between 10 and 12 normal definition signals with an average bit rate of approximately 4Mbps. These channels will burst to 9Mbps when there is a lot of change in the picture of an unpredictable nature. As you can imagine, a boxing match (with a lot of movement) takes significantly more bandwidth, than a network news anchor reading from their desk, so we also try to match channels to fill this available bandwidth.
Typically, we can only fit 3 high-definition channels in the same 40Mbps channel and these have an average bit rate of about 12.5Mbps and as you've noted above, are limited to 24Mbps.
Hope this helps!