Sunday, February 16, 2014

eMAM’s Support for DPX Sequences

eMAM’s Support for DPX Sequences

Digital Moving-Picture Exchange (DPX) file format is one of the industry standard data format for handling a single frame of a motion picture or video data stream. DPX file format supports the exchange of resolution-independent, pixel-based (bitmapped) images, intended for very high quality moving image content for post-production, theatrical distribution and for long term preservation; DPX masters provide the input for digital cinema digital projection systems. This format is used in Motion Pictures and Effects industry that make particular use of the extensive header information and format's flexibility to handle high dynamic range and logarithmic color values at a variety of bit depths using RGB or YCbCr pixel descriptions. It is based on, but largely supersedes, Kodak's Cineon format that has more film specific header.

DPX images may be produced by scanning film, using a camera that produces a DPX output or by a post-production application like Adobe Premiere Pro, After Effects and Speed Grade. Adobe supports the playback of entire DPX sequence as single footage and allows full control over parameters like bit depth, black point and log/linear space allows non-destructive changes to be made at any stage of production. Embedded metadata like timecode associated with each DPX frame allowing more control during the production process.

Challenges in Archiving DPX Sequence

DPX file format is suitable for almost any raster digital imaging application. It provides a great deal of flexibility in storing color information for exchange between production facilities.  Also, DPX Specification allows for a wide variety of metadata to further clarify information stored (and storable) within each file. However, the larger number of files is a major overhead for the database and archive system.

For example, an image file sequence requires one file per frame. Approximate 86,328 DPX files required to store 1 hour video in 23.98 fps. 674GB storage space is required to preserve that video in full HD (1920 x 1080). High speed SAN storage is required to ensure the reliable playback of the DPX sequence because each frame and associated metadata loading is over head for the storage.

Once the project is finished, it may not be required to keep the source DPX sequences in the expensive high speed storage.


Advanced archive solution eMAM Vault allows the users to move the DPX sequences from high speed storage to less expensive LTO storage for long term preservation and protection. eMAM has a built in algorithms to consolidate a DPX sequence to a single H.264 proxy video for web based playback, with each frame in the proxy video is linked to a DPX file. The algorithms help to consolidate the DPX files into a ZIP64 archive file before sending to deep LTO archive library. This reduces the overhead in the database and archive systems from processing large number of files and increased amount of metadata. eMAM can process multiple DPX sequences in a folder automatically, and also detect any broken DPX sequences and warn the user before sending the files to archive.

Empress is planning to extend the support for partial restore of the DPX sequence based on the set in/out points in eMAM rough cut window.

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