3 Operation

First, it is important to distinguish between the various files involved in the conversion operation accomplished by GNU ccd2cue. The whole process basically consists of a conversion of the CCD set of files into a CUE set of files, whose meaning, by suffix, is described below:

In the CCD set all files have the same basename and the respective suffixes are mandatory. It is composed of:

.img

Audio/data raw image (hereafter called image file);

.sub

Sub-channel data (hereafter called sub-channel file);

.ccd

Layout description (hereafter called CCD sheet file);

In the CUE set all files need not have the same basename and the respective suffixes are just an optional default. It is composed of:

.bin

The same image file as above with the traditional suffix;

.cdt

CD-Text meta-data file (hereafter called CD-Text file);

.cue

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 least 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 this only relies on the information contained inside the CCD sheet file to generate the equivalent CUE sheet file. Thus, GNU ccd2cue does not enforce, and in fact 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 corresponding image file in order to burn 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, do not expect to obtain an exact copy, at the 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 important 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.