x264速率控制模式 [英] x264 rate control modes

问题描述

最近，我正在阅读x264源代码.通常，我关注的是RC部分.我对参数 -bitrate 和 -vbv-maxrate 感到困惑.设置 bitrate 时，将在帧级别使用CBR模式.如果要启动MB级RC，请使用参数 bitrate ， vbv-maxrate 和 <应该设置em> vbv-bufsize .但是我不知道 bitrate 和 vbv-maxrate 之间的关系.同时设置 bitrate 和 vbv-maxrate 的真实编码结果的标准是什么? 那么 bitrate 的推荐值是多少?等于 vbv-maxrate ? 另外， vbv-bufsize 的推荐值是多少? vbv-maxrate 的一半? 请给我一些建议.

Recently I am reading the x264 source codes. Mostly, I concern the RC part. And I am confused about the parameters --bitrate and --vbv-maxrate. When bitrate is set, the CBR mode is used in frame level. If you want to start the MB level RC, the parameters bitrate, vbv-maxrate and vbv-bufsize should be set. But I don't know the relationship between bitrate and vbv-maxrate. What is the criterion of the real encoding result when bitrate and vbv-maxrate are both set? And what is the recommended value for bitrate? Equals to vbv-maxrate? Also what is the recommended value for vbv-bufsize? Half of vbv-maxrate? Please give me some advice.

推荐答案

比特率在进行编码时指向目标文件大小".可以理解，这是令人困惑的，因为它应用了一定大小的预算"，然后尝试将该预算分配到帧上-这就是为什么电影的后期部分会获得较少的数据量，从而导致视频质量降低的原因.例如，如果您有10秒钟的全黑图像，然后是10秒钟的自然视频，则最终编码的文件将与顺序相反的情况大不相同.

bitrate address the "target filesize" when you are doing encoding. It is understandably confusing because it applies a "budget" of certain size and then tries to apportion this budget on the frames - that is why the later parts of a movie get a smaller amount of data which results in lower video quality. For example, if you have 10 seconds of complete black images followed by 10 second of natural video - the final encoded file will be very different than if the order was the opposite.

vbv-bufsize是在流传输情况下必须发生的传输"之前必须完成的缓冲区.现在，让我们将其绑定到I帧和P帧:vbv-bufsize将限制任何编码视频帧的大小-最有可能是I帧.

vbv-bufsize is the buffer that has to be completed before a "transmission" would occur say in a streaming scenario. Now, let's tie this to I-frames and P-frames: the vbv-bufsize will limit the size of any of your encoded video frames - most likely the I-frame.

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