CompressAI
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Does CompressAI support direct compression of [y] instead of [y-mean]?
As stated, how can we use CompressAI to compress [y] instead of [y-mean]. Furthermore, how can we understand the advantages of compressing [y-mean]? Thank you very much for your answer!!!
round(y-means) == round(y)
if means = 0
. (Or means == None
works too.)
For example, just set means=None
when using the desired entropy model:
y_hat, y_likelihoods = self.gaussian_conditional(y, scales_hat, means=None)
In terms of advantages, that depends on the situation. If the source y
has its most-likely-value occurring exactly at the mean, then [y - mean]
will probably produce less reconstruction error since we can then reconstruct the most-likely-value with exact precision. On the other hand, if the actual values occur at locations other than the mean
, then both methods will produce similar results. So... it depends.
See here for an example: https://github.com/InterDigitalInc/CompressAI/discussions/227#discussioncomment-5654273
Somewhat related concept: the deadzone quantizer used by JPEG allows near-zero DCT-transformed-and-rescaled coefficients to be rounded to zero, which helps reduce the rate since the most-likely-symbols are near zero, and reconstructing them as zero is worth the R-D tradeoff.
(Deadzone quantizer on the left. Lloyd-Max quantizer on the right.)
Great answer! Thanks a lot! In general, compressing [y-mean] achieves better R-D tradeoff. However, in some cases, we have to compress [y] whose mean is not none. For example, in Checkerboard Context Model, we should compress [y] for one-pass encoding, and compressing [y-mean] leads to two-pass encoding. Can you make some suggestions for AE/AD of [y] using CompressAI?Thank you very much for your answer!!!
As stated, how can we use CompressAI to compress [y] instead of [y-mean]. Furthermore, how can we understand the advantages of compressing [y-mean]? Thank you very much for your answer!!!
Hello, I would like to ask you a question about the installation of compressai “Successfully installed compressai-1.2.4.dev0” . I successfully installed cmpressai, but I got the following error when importing:
import compressai Traceback (most recent call last): File "
", line 1, in File "F:\compressai\compressai_init_.py", line 30, in from compressai import ( File "F:\compressai\compressai\latent_codecs_init_.py", line 38, in from .rasterscan import RasterScanLatentCodec File "F:\compressai\compressai\latent_codecs\rasterscan.py", line 38, in from compressai.ans import BufferedRansEncoder, RansDecoder ImportError: DLL load failed while importing ans: 找不到指定的程序。