Sony’s recent release of multi-codec cameras (the F5 and F55) is a reminder that there is no such thing as the ideal codec. Not only do the cameras support RAW and existing codecs, but Sony introduced XAVC codec to give additional capability and 4K compressed recording.
The choice the Director of Photography (DoP) uses ultimately depends on a number of issues particularly the program genre. An observational documentary is less demanding on final picture quality than prime-time drama.
In an ideal world one codec would be used from camera to master control. That would avoid concatenation of coding artifacts. However in most applications it is just not practical. In any workflow there are touchpoints:
- camera files
- editing files
- delivery broadcast transmission master
- playout server files
Each of these may use a different codec. For example: shoot HD at MPEG-2 4:2:2, 50Mb/s, long GOP; edit and finish at DNxHD 145, deliver as HDCAM-SR and ingest to the playout server as 25Mb/s 4:2:0 long GOP at 20Mb/s. This is decoded to HD-SDI for the master control switcher and keying, and then finally encoded to HD at a nominal 6Mb/s. variable bit rate in a statistical multiplexer.
The first generation of HD camcorders based on videotape had a choice of DVCPRO100 or HDCAM recording. WIth data rates of 100 and 140 Mb/s respectively not only was compression a necessity, but the images were down-sampled from 1920 to 1440 line lengths to lower bandwidth. HDCAM-SR allowed recording at 440 or 880Mb/s, and resolved many of the quality issues.
Before considering the compression format, what is being compressed?