DV Analyzer Case Study: Temporal metadata and use of Final Cut Pro XML
BACK TO DV ANALYZER
As DV video is generated in the camera and written to tape, the camera has the ability to document the date and time of the recording, the timecode, and the camera settings (white balance, focus, etc) into each frame of DV video. With the right workflow this information can be preserved in a file-based environment if the DV tape is ingested as a DV stream (or DV stream inside a container such as MXF, MOV, AVI or others). This information can potentially survive the editing process, but only if the frame isn’t transcoded from the original frame into another new DV frame. When Final Cut renders DV video (before application of color correction, added graphics, or any visual manipulation) then a new DV frame is generated from the original frame. However, the original metadata does not typically survive this process.
This means that for both DV files ingested directly from tape and for final edits that did not alter the original frame (or block the DV metadata in another way) the file may be evaluated to report on DV metadata for each frame on fields such as recording date and time, timecode of the source tape, and camera settings.
This DV file was edited at WITNESS as a compilation tape. Material was shot on DV camera, ingested to files using Live Capture Plus, edited in Final Cut Pro, then exported to a Quicktime movie using the same DV codec (through the File>Export method). This workflow preserves the camera’s metadata throughout the process so that the resulting export still contains information written by the camera, although typically this information is difficult to access.
By evaluating this exported file in DV Analyzer, it will read the metadata from every frame and then report on inconsistencies, such as when one frame has a recording date and time that doesn’t follow the previous frame or when one frame has a timecode value (within the DV codec) that is not sequential with the prior frame. These jumps in the metadata value sequences indicate edit points or places where the camera was stopped and restarted.
By exporting a Final Cut Pro XML document from DV Analyzer, the reported information can be directly associated with its reference frame. In this way, DV Analyzer can serve as a tool to generate a reverse EDL well after the edit was performed or to document events that occurred during the original camera shoot. DV Analyzer uses markers to identify potential points of edits and also to present areas where error detection or quality control may be an issue. This ability to recreate the history of the document after such information may have been lost or forgotten, and the ability to identify problem areas in the DV stream are valuable tools in the preservation of DV and in creating more efficient workflows in those efforts.