A problem loading Yi 4K DNGs. Thumbnails load fine.
I loaded a couple of files up to the raw files submission page and some kind soul put a note on there regarding quantized components.
I guess it’s a problem, question is, is it something that will be fixed? I’ve done some searches online and here and it must be a fairly uncommon error. Any pointers appreciated in this regard.
Tested on 2.5.0+357~ga2b1942a1 and 2.4.2
Many thanks in advance for replies
That’s not an error. Let’s walk through it.
We only parse SOF3
which is, as per https://www.w3.org/Graphics/JPEG/itu-t81.pdf, page 11:
SOF3 lossless process frame marker, Huffman coding
And if we look in the parseSOF(), we find that error message:
Let’s go back to the spec, page 36:
Tqi: Quantization table destination selector – Specifies one of four possible quantization table destinations
from which the quantization table to use for dequantization of DCT coefficients of component Ci is retrieved. If
the decoding process uses the dequantization procedure, this table shall have been installed in this destination
by the time the decoder is ready to decode the scan(s) containing component Ci. The destination shall not be respecified,
or its contents changed, until all scans containing Ci have been completed.
and the following Table B.2 states that for Parameter Tqi, within losslessly compressed image.
(and since we are in SOF3, the image is losslessly compressed.) the valid Values are 0.
So unless i’m missing some fine-print that says ignore the "Tq" value when in SOF3,
i’m inclined to say it is Yi who are at fault here.
Either they are just writing random garbage in that field, or using the wrong frame marker
(if that is indeed compressed with quantized components).
Maybe you should just mail them, and ask them? (do CC me please, if you do)
That’s great. I’ll pass it on.
I didnt CC because I couldn’t find email address. After a few back and forths and pointed to this thread Yi tech said, ‘it’s fine’. Fobbed off unfortunately