Doom9's Forum - View Single Post - BDSup2Sub - convert and tweak bitmap subtitle streams (VobSub,BD-SUP,BDN XML,HD-SUP)

CatBus · 20th February 2021, 18:32

I think I've found a bug in the Java version of BDSup2Sub (can't confirm C++). It looks like the colors of the subtitles get subtly changed when converting from BDN+XML to BD-SUP, in scenarios where I can't see a reason for this happening. You can magnify this by round-tripping the conversion multiple times.

Example: if the text in a BDN+XML subtitle is #E4E6E0, it gets converted to #E5E6E3 when you turn it into a BD-SUP. If you convert that BD-SUP back into BDN+XML, the color stays #E5E6E3. But then if you convert it back into a BD-SUP again, it then becomes #E5E5E5. Basically, every conversion from BDN+XML to BD-SUP slightly desaturates the colors.

I can't really tell where the conversion error is, but it may be in creating the image palette from the PNG files.

20th February 2021, 18:32	#1484 \| Link
CatBus Registered User Join Date: Jan 2012 Posts: 8	I think I've found a bug in the Java version of BDSup2Sub (can't confirm C++). It looks like the colors of the subtitles get subtly changed when converting from BDN+XML to BD-SUP, in scenarios where I can't see a reason for this happening. You can magnify this by round-tripping the conversion multiple times. Example: if the text in a BDN+XML subtitle is #E4E6E0, it gets converted to #E5E6E3 when you turn it into a BD-SUP. If you convert that BD-SUP back into BDN+XML, the color stays #E5E6E3. But then if you convert it back into a BD-SUP again, it then becomes #E5E5E5. Basically, every conversion from BDN+XML to BD-SUP slightly desaturates the colors. I can't really tell where the conversion error is, but it may be in creating the image palette from the PNG files.