Firstly, it is important to discern between the various files involved in the conversion operation accomplished by GNU ccd2cue. The whole process consists basically of a conversion of the CCD set of files into a CUE set of files, whose meaning is, by suffix, described below:
In the CCD set all files have the same base-name and the respective suffixes are mandatory. It is composed by:
Audio/data raw image (hereafter called image file);
Sub-channel data (hereafter called sub-channel file);
Layout description (hereafter called CCD sheet file);
In the CUE set not all files have necessarily the same base-name and the respective suffixes are just an optional default. It is composed by:
The same image file as above with the traditional suffix;
CD-Text meta-data file (hereafter called CD-Text file);
Layout description (hereafter called CUE sheet file);
The GNU ccd2cue program never touches any of the files in the CCD set; not even to rename the image file to use the traditional .bin suffix. However it will still work with other software because the image file is explicitly referenced inside the CUE sheet file. The idea is to take the less intrusive approach, e.g., to have both sets of files simultaneously without any interfering with each other. Although we are against the use and development of any proprietary program, including those which can handle CCD sheets9, it can be useful to have the original CCD sheet for reference, in case the conversion process is improved in a subsequent release; or more expressive destination formats10 become supported; or just for debugging.
The GNU ccd2cue program has just one non-trivial operation: the conversion and only rely on the information contained inside the CCD sheet file to generate the equivalent CUE sheet file. Thus, GNU ccd2cue does not enforce, and actually does not even check, if you have the sub-channel file, or even more important, the actual image file. Therefore, although it is possible to generate seamlessly a CUE sheet file from a lone CCD sheet file, it is a must to have also, at least, the correspondent image file when burning the disc.
While the image file is not used by GNU ccd2cue but is referenced in the produced CUE sheet file, the sub-channel file is not used nor referenced at all in the CUE sheet file. The CUE sheet format was not designed to describe the information found in the sub-channel file and most optical disc authoring software seems to ignore it when guided by a CUE sheet file. Therefore, does not expect to obtain an exact copy, at sub-channel level, using the CUE sheet file to guide your burning software. Nevertheless, for the vast majority of practical uses the extra sub-channel data contained in the sub-channel file can be fully ignored producing yet usable discs for the intended application. Notice however that that does not mean CUE sheet format is incapable of describing any sub-channel data; in fact it describes the most remarkable ones. Hence all that data is available for GNU ccd2cue not inside the sub-channel file but rather in the CCD sheet file itself; the CD-Text meta-data is such a case — the CD-Text file is produced from decoded sub-channel information available inside the CCD sheet file.
Actually I’m really sorry those programs came into existence in the first place. I wish I never had to write a program like GNU ccd2cue. I would then be contributing to society in a way that directly advances the social good, not just alleviating the wrong doing of others that immersed in their own egoism and blindness desire to subjugate their neighbors for their own benefit.
The TOC sheet format is an example.