H264 RTP和打包模式(基线H264 RTP中没有STAP-A) [英] H264 RTP and packetization mode (no STAP-A in baseline H264 RTP)

问题描述

有一个规范确实需要这样做:

There is a spec that literally requires this:

当SDP协商导致使用基准配置文件时 (BP)，客户端不得发送A型一次性聚合数据包 (STAP-A)数据包，即使已将打包模式1设置为 洽谈.接受使用约束基准配置文件时 (CBP)客户端应支持在以下情况下使用STAP-A数据包 协商了打包模式1.

When the SDP negotiation results in the use of the Baseline Profile (BP), a client shall not send Single-Time Aggregation Packet type A (STAP-A) packets, even when the packetization-mode 1 has been negotiated. When accepting the use of the Constrained Baseline Profile (CBP) a client shall support the use of STAP-A packets when packetization-mode 1 was negotiated.

有人可以评论吗?听起来像是胡说八道吗?基线或受约束的基线解码器甚至怎么可能知道h264是在STAP-A中传递的(或者完全是RTP传递的).

can anybody comment that? Doesn't that sound like complete nonsense? How is that even possible that baseline or constrained baseline decoder could know that h264 was delivered in STAP-A (or at all that it was delivered by RTP).

推荐答案

由于您没有提供参考，所以这完全是不是. STAP-A还意味着NAL单元很小(因为它们必须适合单个数据包).因此，在接收器侧(RTP层)和解码器大小上需要较少的存储器(显然，如果每个NAL很小，则比特率将较低，因此所需的处理能力也较低). 基线特征已经很小，但是CBP甚至更小. 该规范仅说明如果使用BP，则仅应使用FU-A(=>大NAL =>更高的比特率=>需要更多的内存/CPU)，如果使用CBP，则也允许使用STAP-A(减少负载).

Althrough you don't provide a ref, this is not total nonsense. STAP-A also means that NAL units are small (since they must fit in a single packet). Thus, less memory is required on the receiver side (RTP layer) AND decoder size (obviously the bitrate will be lower thus required processing power, if each NAL is small). Baseline profile is already very small, but a CBP is even smaller. This spec says simply that if BP is used, then FU-A should be used only (=> large NAL => higher bitrate => more memory/CPU required), and if CBP is used, then STAP-A is allowed too (less load).

最后，解码器不知道使用了什么传输，但是如果仅使用STAP，则对解码器处理能力的要求会更少.

In the end, the decoder does not know what was the transport used, but if only STAP was used, the requirements on the processing power of the decoder is less.

但是，我同意应根据解码器要求而不是网络分段要求来写.

I agree however that this should be written in terms of decoder requirements and not network fragmentation requirements.

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