问题描述
我已经使用Android中的NV21图像工作了一段时间，我一直在跟踪可能由NV21图像中的错误索引字节引起的错误。
- 当图像具有奇数尺寸（如奇偶校验）时会发生什么？这种格式甚至可以吗？
- 我们在某处有这种格式的官方规范吗？
对于具有奇数尺寸的图像（即W或H中的一个，在WxH图像中是奇数），您希望Y平面一如既往地被完全采样，使用WxH样本，然后是2（⌈ W / 2⌉ x⌈ H / 2⌉）色度样本，我们除以每个图像尺寸为2但是向上舍入而不是向下舍入。
因此，图像边缘的一些像素具有仅对应于1或2的色度样本原始像素，而不是4.我希望这是有道理的。您可以在中看到其他几个图书馆之前在YUV图像中处理奇怪维度的问题。
对于你的第二个问题，我还没有看到官方规范，但我在android框架中看到了一些代码处理这种格式，我会看看是否可以找到它的链接，并将其附加到这个答案。
I have been working for some time with NV21 images in Android and I have been tracking a bug that might be caused by incorrect indexing bytes in an NV21 image.
The image in the answer of this question has a nice overview of how the Y, U and V bytes are positioned in the image buffer. Not sure it is allowed, but I am embedding it below:
- What happens when the image has odd dimensions (as in parity)? Is that even possible in this format?
- Do we have an official specification of this format somewhere?
In the case of an image with odd dimensions (i.e one of W or H, in a WxH image is odd), you'd expect the Y plane to be fully sampled as always, with WxH samples, followed by 2(⌈W/2⌉ x ⌈H/2⌉) chroma samples, where we divide each image dimension by 2 but round up rather than round down.
So some of the pixels at the very edge of the image have chroma samples that correspond to only 1 or 2 original pixels, rather than 4. I hope that makes sense. You can see in this link that a couple of other libraries have had issues handling odd dimensions in YUV images previously.
For your second question, I haven't seen an official specification, but I have seen some code in the android framework that handles this format, I will see if I can dig up a link to it, and append it to this answer.
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