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To have a single file format suitable for the preservation of both film and video has been the dream of many archives, especially smaller ones, since the beginning of digital moving images. Today, on the horizon, we can see something that will provide exactly this capability, in a free and open-source environment.
The following article is an updated version of three presentations I made last year on this topic:
* with Kieran O'Leary from the IFI Irish Film Archive1 at the symposium No Time to Wait: Standardising FFV7 and Matroska for Preservation, Berlin, 18-20 July,
* at The Reel Thing technical symposium, Hollywood, 18-20 August,2
* at a meeting of the Memoriav video specialists, Bern,22 November.3
It presents the situation as at the beginning of 2017, and my goal is to discuss the evident potential of this new system, as well as to address the still-unresolved aspects of the Matroska container and the FFV1 video codec.
DEFINITIONS
I describe film as having single-image-based content, mainly represented in the RGB or R'G'B' colour space at 4:4:4 chroma sampling, and, at present, usually stored in a folder: for example, TIFF files in a folder, DPX files in an MXF container, and JPEG 2000 files in an AXF container.4 I call video stream-based content, mainly in the colour space Y'CßCR at 4:2:2 chroma sub-sampling, currently often stored uncompressed in either an MOV (QuickTime), an AVI, or an MP4 container.5 In practice, the choice of container does not matter, because only the file header (and possibly the file footer) are different in different containers, while the stream is bit-by-bit identical for the full image content. The file can be trans-muxed (i.e., the file is de-muxed and then re-muxed) very quickly, because transcoding (i.e., extremely time-consuming decoding and re-encoding) of the file's content is not required. Re-wrapping can be easily done if needed, e.g., during a data migration, without any additional cost. Therefore, the passionate discussions about the best container choice - MP4, AVI or MOV - should now be relegated to the past. The important factor for an archive is that Y'CßCR 4:2:2 content is often used by the video and broadcast community to achieve the best quality of high-level professional production and post-production. An archive should therefore be...