The numbers refer to the number of megabits per second the tape is designed to transport. DVC Pro videotape machines were introduced in 1996. The differences between DV, DVCAM, and DVC Pro are ones of track width and tape speed. Before the digitized video signal hits the tape, it is the same in all three formats.
DVC Pro was from the start intended for ENG use, as well as for industrial or 'prosumer' applications. Designers placed as higher priority better error correction and ease of analog editing. The format quickly found use in NBC's newsgathering operations, which gave the format a tremendous boost. DVC Pro videotape machines will play back DV and DVCAM tapes without an adapter. MiniDV tapes require an adapter for use in a DVC Pro machine. DVC Pro machines do not record on MiniDV tapes.
DVC Pro 50 was the follow-on format, intended to supplant DVC Pro in uses where ENG compatibility was required, but higher resolution was desired for upscaling to HDTV. DVC Pro 50 machines will play back DVC Pro tapes at the 25 Mb data rate. However, DVC Pro machines cannot play back DVC Pro 50 tapes. Panasonic achieved the higher data rate by doubling the tape transport speed.
DVC Pro HD, formerly called DVC Pro 100, couples four DV codecs in parallel to achieve a 100 Mb data rate, which is sufficient for 720p progressive scan digital video, or 1080i interlaced digital video. DVC Pro HD machines will play back any DVC Pro tape at the recorded data rate, or upconvert it to a 100 Mb data rate.