h.264 - 为什么我们会乱序传输 IBP 帧？

Question

我们像 IPBBPBB 一样传输 IBP 帧，然后在 IBBPBBP 中显示它们。这是一个问题，我们为什么要这样做。我不能只是在脑海中想象它。我的意思是，为什么不按照它们要显示的顺序传输它们？

Answer 1

对于时间压缩中的双向帧，解码顺序(数据需要传输以进行顺序解码的顺序)与呈现顺序不同。这解释了您所指的效果。

在下图中，您需要帧 P2 的数据来解码帧 B1，因此在传输时，P2 继续。

查看更多相关信息:B-Frames in DirectShow

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Since MPEG-2 had appeared a new frame type was introduced - the bi-directionally predicted frame - B frame. As the name suggests the frame is derived from at least two other frames - one from the past and one from the future (Figure 2).

Since the B1 frame is derived from I0 and P2 frames both of them must be available to the decoder prior to the start of the decoding of B1. This means the transmission/decoding order is not the same as the presentation order. That’s why there are two types of time stamps for video frames - PTS (presentation time stamp) and DTS (decoding time stamp).