Error: no member named 'numgbits' in 'opj_cparameters' while compiling

[mart-jansink]

While trying to compile libdcp I'm getting the following error:

../src/j2k_transcode.cc:318:13: error: no member named 'numgbits' in 'opj_cparameters'
        parameters.numgbits = fourk ? 2 : 1;

This line was added in 9b1b653 but the only mention of numgbits in openjpeg.h is in the opj_tccp_info struct, at least in https://github.com/uclouvain/openjpeg/blob/0bda7188b7b545232a341f1d978b1e4feda46fc2/src/lib/openjp2/openjpeg.h#L922. Are you perhaps using a patched version of OpenJPEG, or am I missing something else?

[cth103]

Hi Mart, sorry, yes I am indeed using a patched OpenJPEG, I should have mentioned that. I put that OpenJPEG version here: https://github.com/cth103/openjpeg

It has a rather motley collection of patches but a1403c2e2e71c6252d97abf9ddca421ce925d456 is the one you need. Or I can modify libdcp to not require this change, if that would be easier for you?

The change was made because, as far as I can see, it's necessary for DCPs to comply with the SMPTE Bv2.1 guidelines.

[mart-jansink]

Ah, that's perfect, thank you. I had pretty much guessed that you had modified it like this, and am fine running a patched version of OpenJPEG of course. I did encounter a few other issues while compiling, for which I'll make a small pull request.

Regarding Bv2.1, just out of curiosity: uclouvain/openjpeg#1340 mentions that there's also something to do with the cblk needing to be 32,32. Did you also implement that?

[cth103]

Right yes the 32x32 codeblock has been there for a while, and OpenJPEG allows you to set it (see dcp::compress_j2k, parameters.cblockw_init and cblockh_init) so that's OK without changes to OpenJPEG.

[jiapei100]

Hi, @cth103

Yeah.... Better to keep OpenJPEG as it is.... I built OpenJPEG manually as well. Lazy to give some further modification....
Any plan to update libdcp for NO modification upon current OpenJPEG-2.5.0 ???

For now, I just temporarily remove this line:

//	parameters.numgbits = fourk ? 2 : 1;

in file j2k_transcode.cc.

[cth103]

The openjpeg team merged a fix for this recently, so we could make it possible to built with openjpeg git again. I just need to get around to it. The version used with by dcpomatic.com builds also includes an old optimisation which I need to test (to see if it's still useful).

One more thing to consider is that we have been bitten in the past by a change in openjpeg breaking compatibility with cinema hardware so I'm a bit cautious with tracking their git too closely.