Upstream qoi decoder seems fine if stream ends early, investigate

[amstan]

How to reproduce:

• Set QOI_FPGA_ENCODER_POST_CYCLES = 0 so verilator_shim does not compensate for this effect
• perhaps comment out all ops in the verilog except QOI_OP_RGB, so it's more visible

Note how everything's shifted over by 1 cycle, so the last pixel is missing. How come the upstream decoder is still ok with this? How does it manage to make up the last 0xffffff on testcard.qoi?

[amstan]

(Please excuse the extension change)
testcard_rgba.bad.qoi.txt
testcard_rgba.good.qoi.txt

md5sum testcard_rgba.* images/testcard_rgba.qoi
d6c9a6908a6e1829d20d96ceb06041af  testcard_rgba.bad.qoi.txt
c2f8f473c7634156ce15c4c69b8ae6c1  testcard_rgba.good.qoi.txt
c2f8f473c7634156ce15c4c69b8ae6c1  images/testcard_rgba.qoi

The .bad file was generated according to above instructions. Note how it decodes into the exact same .png file using the refenrece decoder.

[amstan]

Heh, my new verilog based decoder produces a different .png hash for the .bad file. An image viewer doesn't really show any difference between the 2. It might be a transparent pixel?