If one reads RDD 52, you will notice that we referenced the concept of a ‘dummy’ subtitle file. At the time of publication the manner in which to go about creating and incorporating such a ‘dummy’ instance was not ratified. Reason for this is that as we migrated to SMPTE DCP, we discover issues surrounding content decryption in the field, specifically around Timed Text files which had significant impact on their display characteristics. To summarize, any reel instance which had no Timed Text tracks that existed between reels that had Timed Text tracks required to be ‘padded’ with Timed Text tracks that had wrapped ‘dummy’ or ‘blank’ D-Cinema XML essence. This contiguous construction of reels, programmatically ensures consistent display characteristics when said content is decrypted.
RP 428-22a is the the recommended practice I was involved in writing that details the creation process of a blank D-Cinema Timed Text XML file.
Be sure to check out my guide here on creating a RP 428-22a compliant D-Cinema XML wrapped in an MXF track file.