What is the PCX Protection?
Question:What is the PCX_Protection?
Answer: There are 2 parameters in the Digas environment that affect the PCX Protection:
PCX_Original refers to a bit inside the MPEG header that determines if at playback in a digital enviroment a bit is set in the data stream that prompts other hardware to possibly deny a recording, etc.
This flag is read directly, i.e. PCX_Original=TRUE cause a bit to be set in the header. The IRT library implemented by Digas sets this bit by default when an MPEG frame is to be created from linear data.
PCX_Protection refers to another bit in the MPEG header that determines whether a 16-Bit Checksum should be inserted after the header. This is important for insecure transmission (via radiowaves for example). This 16-Bit is then no longer available for audio data, thereby perhaps comprimising the audio quality. Unfortunately this provides for a negative logic; i.e. when the bit is set in the header - there is no Checksum available. In our settings the value directly applies the value of the bits; i.e. PCX_Protection=TRUE sets the bit and a checksum is not made.
Note: The Digas Rec_X and Rec_NP modules leave the entire Checksum procedure to the Digigram drivers and make no change thereafter. This should present no problems.
If you should experience problems with older files that may have been created before this Digas parameter was implemented, we have a utility to correct this bit. "MPEG CRC File Repair Tool" is available in our mailbox (Utilities) or per e-mail (write to email@example.com).