Digital intermediate

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The Digital Intermediate (DI) is a digital intermediate stage in the post-production of films between recorded and exposed film. In a first step, the camera negative recorded on film material is scanned with a film scanner . Alternatively, the digital images from a digital cinema camera can be used directly. The resulting material is digitally cut and post-processed ( color correction , CGI , etc.). This creates the so-called DI-Master , which serves as a template both for the subsequent digital evaluation ( DVD , HD DVD , Blu-ray Disc ) and for the production of the copies / masters for analogue or digital cinema projection. To create analog film copies , the DI is exposed on negative film and the resulting internal negative is copied in the copier . Alternatively, a digital master according to DCI is created for the digital cinema projection .

technology

The DI is usually saved uncompressed in individual images. The memory required for this depends on the selected resolution and color depth. The usual resolutions for photochemical film copies are 1920 × 1080 p , 2K (depending on the format 1860 to 2048 horizontal pixels ) and 4K (depending on the format 3612 to 4096 horizontal pixels). For digital performance, 1080p and the specification of the Digital Cinema Initiative are market-defining.

The number of vertical pixels depends on the aspect ratio of the selected image format and the exposed area on the camera.

2K and 4K

The classic 35 mm projection achieved in an independent test by the International Telecommunication Union a maximum image resolution of 875 horizontal lines (light-dark change). The lion's share of all cinema productions is processed in 2K. Sometimes it makes qualitative sense to work and perform with 4K resolution .

From 1990 to 2007 hundreds of feature films were mastered in 2K , now almost a dozen also in 4K. Even in digital cinema, thousands of 2K screens have so far only been compared to dozens of 4K cinemas worldwide.

With the availability of new digital cinema cameras with 4K resolution such as the RED camera, 4K production is becoming more widespread than before.

The market share of 2K editing of feature films has been consistently over 95% since the 1990s. In individual cases, higher resolutions are used, especially for visual effects and for restorations, etc.

data volume

The data volumes and data rates required for DI were originally only conveniently editable with special computer systems, since they are in the terabyte range.

The following image data formats are used:

  • 10-bit gamma-coded 4: 4: 4 RGB signal (common format, but a format without reserve)
  • 10-bit gamma-encoded 4: 2: 2 YUV signal
  • 12-bit gamma-coded 4: 4: 4 RGB signal (should replace 10 bit)
  • 16-bit linear 4: 4: 4 RGB signal
  • 12-bit non-linear Bayer matrix signal
  • 16-bit linear Bayer matrix signal (mostly lossless (?) Compressed with L³)

Instead of an RGB color space , current productions use the XYZ color space , which can represent all existing colors. The gamma value for gamma-coded signals is 2.6. Audio is generally saved uncompressed with 24 bits.

The memory requirement for a 3 × 10-bit RGB gamma-coded production (without compression) with 24 frames per second is:

Format and aspect ratio resolution Throughput Amount of data for 2 hours
1080p at 16: 9 1920 × 1080 187 MB / s 1.34 Tbytes
1080p at 1.85: 1 1920 × 1040 180 MB / s 1.29 Tbytes
1080p at 2.35: 1 1920 × 816 141 MB / s 1.02 Tbytes
1080p at 2.40: 1 1920 × 800 138 MB / s 1.00 Tbytes
2K with 16: 9 1920 × 1080 187 MB / s 1.34 Tbytes
2K with 1.85: 1 2000 × 1080 194 MB / s 1.40 Tbytes
2K with 1.90: 1 2048 × 1080 199 MB / s 1.43 Tbytes
2K with 2.35: 1 2048 × 872 161 MB / s 1.16 Tbytes
2K with 2.40: 1 2048 × 854 157 MB / s 1.13 Tbytes
4K at 16: 9 3840 × 2160 747 MB ​​/ s 5.37 Tbytes
4K at 1.85: 1 4000 × 2160 778 MB / s 5.60 Tbytes
4K at 1.90: 1 4096 × 2160 796 MB / s 5.73 Tbytes
4K at 2.35: 1 4096 × 1744 643 MB / s 4.63 Tbytes
4K at 2.40: 1 4096 × 1708 630 MB / s 4.53 Tbytes
8K with 2.35: 1 8192 × 3488 2572 MB / s 18.52 Tbytes
Additionally for audio
6-channel sound, 48 kHz, 24 bit - 7 MB / s 0.05 Tbytes
6-channel sound, 96 kHz, 24 bit - 14 MB / s 0.10 Tbytes

The data volumes and data rates are calculated for the smallest RGB format (3 × 10 bit). With higher color depths (which are aimed for), the storage space requirement increases. Using lossless or almost lossless compression techniques, the storage space requirement can be reduced by a factor of around 2.

The storage space requirement refers to 2 hours of cut film. However, you have to be aware that a multiple of this amount is in circulation in a film production:

  • The video material produced on the set usually runs 10 to 50 times the duration of the final film.
  • In addition to the final version, many intermediate results and alternative editing versions are created in the editing process.
  • You also want to be able to access source material from other films without any effort, i. H. you want to have the entire film material of all productions of the studio in a huge pool (so-called image library).

history

The DI process has now established itself. Films that are still copied directly from the negative without a digital intermediate step have become a rarity. Of the ten most successful films worldwide of 2006, the three animated films were produced entirely digitally (this creates a DI master without the scanning step); the remaining seven real-life films , three of which were partially shot and one completely digitally, have all been copied via a DI master.

Work steps and devices

A digital intermediate work chain typically consists of 3 steps:

  • The digitization of the images of a rotated film with a film scanner or alternatively direct digital rotation with a digital cinema camera
  • Editing of the film with a digital intermediate system
  • The exposure of the processed film on a film exposure unit or the creation of a digital master

Web links from providers of DI systems

There are (as of 10/2007) only a dozen providers of DI systems. The smaller providers have no distribution within the EU.

  • filmlight baselight
  • iridas speedgrade
  • davinici various devices, also a focus on restoration
  • dvs clipster
  • quantel iQ / pablo
  • apple color
  • discreet luster
  • chrome matrix
  • assimilate scratch
  • nucoda master series
  • SGO Mistika
  • pogle different devices

Individual evidence

  1. Study by the ITU (English) ( Memento of the original from October 15, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 288 kB)  @1@ 2Template: Webachiv / IABot / www.cst.fr
  2. ^ A b Jan-Keno Janssen: role reversal. Goodbye celluloid, here comes HD . c't 20/2007, p. 80
  3. http://www.filmlight.ltd.uk/
  4. Archived copy ( memento of the original from October 13, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / spotlight.iridas.com
  5. http://www.dvs.de/
  6. http://quantel.com/
  7. http://www.apple.com
  8. Archived copy ( Memento of the original from April 20, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / usa.autodesk.com
  9. http://www.chrome-imaging.com/
  10. http://www.assimilateinc.com/scratch.html
  11. http://www.digitalvision.se/
  12. http://www.sgo.es/index.php?id=36
  13. Archived copy ( Memento of the original from July 15, 2012 in the web archive archive.today ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / pogle.pandora-int.com