建议的压缩率与H.264？ [英] Suggested Compression Ratio with H.264?

问题描述

注意益处：我意识到这是一个非常复杂的问题，约有一百万个细微差别，我试图减少到一个数字...

我要使用H.264编码进行大型视频编码项目。我们正在尝试创建多个比特率配置文件，以适应互联网连接，处理器，设备等的流。

一般来说，我应该期待什么样的压缩比看到（同时保持在合理的质量水平）？

例如，每秒24帧和16位颜色的640x360（16：9）像素视频文件应产生未压缩文件即大约33 MB / s。

我被告知，对于该文件，500 Kbits /秒（或62 KB /秒）不是不合理的视频比特率。这似乎疯了 - 超过530：1压缩？这是99.8％的压缩。我的数学错了吗？

我只是想寻找一个粗略的外部指南的质量，如超过500x压缩是疯狂的或小于400x是一种浪费的带宽。我看过无处不在，没有什么给我任何种类的预期压缩...

解决方案

a href =http://www.adobe.com/content/dam/Adobe/en/devnet/video/articles/h264_primer/h264_primer.pdf> H.264 Primer ，一个简单的公式给出为根据视频的特性计算理想输出文件比特率的提示：

[image width] x [image height] x [framerate] x [motion rank] x 0.07 = [所需比特率]

其中图像宽度和高度以像素表示，运动等级是在1和4之间的整数，1是低运动，2是中等运动，4是高运动（运动是在帧之间变化的图像数据的量，参见所链接的文档以获得更多信息）。 / p>

例如，如果我们采用24 FPS的1280x720视频，中等运动（具有慢相机移动，不是很多场景变化的电影），预期理想位元率为：

1280 x 720 x 24 x 2 x 0.07 = 3,096,576 bps =>大约3000 kbps

这纯粹是一个提示，在我看来，准确找到理想比特率的唯一方法是错误尝试：）

Note bene: I realize this is an immensely complicated question with about a million levels of nuance that I'm trying to reduce to a single number...

I'm about to undertake a large video encoding project using H.264 encoding. We are trying to create multiple bitrate profiles in order to accommodate streaming across internet connections, processors, devices, etc.

Generally speaking, what kind of compression ratio should I be expecting to see (while staying within a reasonable level of quality)?

For example, a 640x360 (16:9) pixel video file @ 24 frames per second and 16-bit color should yield an uncompressed file that is approximately 33 MB/s.

I've been told that, for that file, 500 Kbits/second (or 62 KB/s) is not an unreasonable video bitrate. That seems insane - more than 530:1 compression? That's 99.8% compression. Is my math wrong?

I'm just looking for a rough outer guide for quality, like "more than 500x compression is crazy" or "less than 400x is a waste of bandwidth". I've looked everywhere, and nothing gives me any kind of expected compression...

解决方案

In a quite interesting document called H.264 Primer, a simple formula is given as an hint to compute the `ideal' output file bitrate, based on the video's characteristics:

[image width] x [image height] x [framerate] x [motion rank] x 0.07 = [desired bitrate]

where the image width and height is expressed in pixels, and the motion rank is an integer between 1 and 4, 1 being low motion, 2 being medium motion, and 4 being high motion (motion being the amount of image data that is changing between frames, see the linked document for more information).

So for instance, if we take a 1280x720 video at 24 FPS, with medium motion (movie with slow camera movements, not many scene changes...), the expected ideal bitrate would be:

1280 x 720 x 24 x 2 x 0.07 = 3,096,576 bps => approximatively 3000 kbps

This is purely a hint, and in my opinion, the only way to accurately find the ideal bitrate is trial by error :)

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