Digital Cinema 2001 NIST – Gaithersburg MD Steve Mahrer

1. The Use of Format Conversion In Digital Cinema Digital Cinema 2001 NIST – Gaithersburg MD Steve Mahrer Panasonic Broadcast & Television Systems Co.

2. Format Conversion • Image Format Conversion is a mathematical process for the resizing (scaling) of an image size. Various interpolation techniques may be used to derive data for the new image. • With the advent of DSP and PCs, format conversion is an everyday occurrence. Anybody working with graphics or simply browsing the Internet will, often unknowingly, use format conversion on a real time basis. • Format conversion in a PC is both fast and efficient, but often not of the highest quality. The reasons being the display in use and simple economics. A 17” XGA monitor, while demanding, is not a 15 x 40 foot cinema screen!

3. Format Conversion Facts of Life… • Format conversion is neither easy, nor transparent. (The Laws of Physics are actually quite difficult to overcome!) • Source and destination video formats will impose conversion issues; e.g. de-interlacing, anti-alias (Nyquist) filtering,inverse 3:2 pulldown sequencing, changing colour space etc. • Often the ‘best’ mathematical solution, doesn’t look the best! • Signal content may, (often does), dictate optimization for best results. • Discrete pixel addressed display devices, such as DLPs, LCDs, D-ILAs, etc don’t have image reconstruction filters. Filtering can thus becomes a factor in optimizing format conversions.

4. Format Conversion 101… Spatial Interpolator (Scaler) Original image 205 x 154 pixels Interpolator generates values for OP format pixels Resultant image 410 x 308 pixels Note that the resized image is softer. It contains the original image content, just ‘spread’ over a double sized ‘canvas’. Despite what marketers say, you cannot create resolution!

5. Basic Interpolator and I/O Filters 2D Interpolator Input H & V Filter Output H & V Filter IN Out

6. x x x Q x x x x x x x - input pixel - output pixel 2-D Resampling 2-D Resampling

7. x x x Q x x x x x x x - input pixel - output pixel 2-D Resampling 2-D Resampling

8. Bi-linear Interpolation I0 I1 x x Q = new pixel Q x x I3 I2 Bi-linear Interpolation

9. Upsampling (conversion) Apart from I/P Nyquist limit,few filter constraints due tolow BW content. O/P may require equalization (HF boost) upsample Downsampling (conversion) Severe filter constraints due to truncation of HF content. Ringing is a serious problem, requiring careful filter choice downsample Limits of Bi-linear Interpolation

10. Filtering and Equalization is a Subjective Choice. Soft Response Sharp Response

11. Ringing, OP Filter Too Sharp,use Filter with ‘Gentler’ Slope Ringing No Ringing

12. Nyquist Limits. Alias appears as LF beat Content above Fs/2 F sample Fs/2 Nyquist limit 0 If the content has information in excess of half the pixel clock rate, an aliaswill occur. Nyquist filtering is important for both the input and output. Especially important for pixel addressed displays, numerous Plasma / LCD/ DLP displays alias severely if stressed.

13. Aliased Non Aliased Nyquist Filtering & Aliasing. Input Filter Too Wide, Reduce…

14. Film to Tape, 3:2 and Inverse 3:2 • Often it is required to display older or archived HD material. Until recently almost all HD recorders recorded an interlaced HD signal, either1035 or 1080i. If the HD material originated during a film to tape transfer, a process known as 3:2 pulldown was used during recording. • For optimal quality, it is desirable to remove the 3:2 interlaced structure of the HD material and revert back to a 24 frame HD signal for display. The 1080p 24 content is then format converted to suit the projector in use. • More modern HD film to tape recording is accomplished by means of progressive recording, often at 24fps, the native film rate.

15. F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 3:2 Pulldown, Film to Tape… Film 24 fps Videotape 30fps 2 3 2 3... • Film is generally shot at 24 fps, Video is typically 30 fps (60 fields /sec) • 3:2 pulldown is a special film advance sequence to provide “real-time” 24 fps film viewing at TV’s 30fps • The 3:2 pulldown sequence may be “undone” to yield 24P from 60i input

16. Ghosting = Incorrect 3:2 removal or Too Wide a Temporal Filter on De-interlacer Ghosting No Ghosting

17. Video Artifacts… • In certain cases, the video signal destined for format conversion and display may already have embedded video artifacts. • Format conversion of such artifacts will only create more undesirable artifacts and degrade the image quality further. • It is advisable to reduce or remove any such artifacts before format conversion and display.

18. Interlace Image (HDTV 1080i) Photo Courtesy NASA MSFC Interlace Freeze-Frame Note the distortion visible on the vertical resolution wedges.

19. Progressive Image (HDTV 720p) Progressive Freeze-Frame Photo Courtesy NASA MSFC Note the lack of distortion in vertical resolution wedges

20. Interlace Image (HDTV 1080i) Close-Up Interlace Freeze Frame Photo Courtesy NASA MSFC Please note fine engraving next to Jackson’s head Compare to new style $20 bill.

21. Interlace Image (HDTV 1080i ) Please note direction of the fine engraving next to Jackson’s head Compare to new style $20 bill. The engraving pattern is inverted! Close-Up Interlace Freeze Field Photo Courtesy NASA MSFC

22. Progressive Image (HDTV 720p) Close-Up Progressive Freeze Frame Photo Courtesy NASA MSFC Please note direction of the fine engraving next to Jackson’s head Compare with new style $20 bill. Engraving pattern is correct.

23. Digital Cinema, Conversion Quality Issues; • A 15 x 40 foot screen will make any format conversion artifacts VERY visible, indeed they can seriously impair the displayed image quality and detract from the overall “Cinema viewing experience”. • Optimal format conversion is obtained when: • Internal processing ‘buses’ must be wide enough to maintain a full 10 bit I/O without truncation or clipping in digital filters, multipliers etc. i.e.“Digitally “linear” • Optimal filtering is used for both input and output formats. • The output filtering is optimized for the display device in use. E.g. never exceed the display’s max resolution, otherwise severe aliasing will occur. This is especially important with pixel addressed displays.

24. Universal Format Converter… • The 32 formats of the ATSC, combined with numerous “VGA based” pixel addressed display devices almost guarantees that a signal will be format converted at least once before display. • Panasonic has designed a custom LSI format converter “chip”, to provide a very high quality “drop in” technical building block solution to format conversion. • This ASIC is now widely used in Digital VTRs, Cameras, Plasma, LCD and DLP displays devices. Basically anywhere where “format flexible” ultra high quality format conversion is required. • The UFC-1800 is also sold as a “stand-alone” post production format converter. An engineering / creative tool

25. Video Path Sync & Active Video Detection Horizontal Resizing Filter Transpose Frame Buffer Vertical Resizing Filter Transpose Frame Buffer Matrix Sync Insertion Out PC Controller Synchronizer In Delay Out Audio Path Panasonic UFC Building Block Concept In

26. UFC-1800 Capabilities • Spatial scaling of any Video Format • Temporal multiples also, 30 to 60, 24 to 60 etc. • Adjustable H & V resizing – 0.25 x to + 8x 0.0001increments • Adjustable Crop H & V Crop • Assignable Matrix; ‘Custom’, REC 709, 601 or 240M • Adjustable Input filtering and EQ. O/P has 2D HF EQ. • Choice of field / frame up / down-conversions • Chip-set now widely used in many broadcast & industrial applications. A “Technology Building Block”

27. Supported Video Formats Frames/sec

28. Questions? mahrers@panasonic.com More details? Visit our Web site http://www.panasonic.com/broadcast