Digital File Formats


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Digital File Formats

  1. 1. Digital File Formats
  2. 2. BITS DEPTH• Every color pixel in a digital image is created through some combination of the three primary colors: red, green, and blue.• Each primary color is often referred to as a "color channel" and can have any range of intensity values specified by its bit depth.
  3. 3. BITS DEPTH• The bit depth for each primary color is termed the "bits per channel." The "bits per pixel" (bpp) refers to the sum of the bits in all three color channels and represents the total colors available at each pixel.• Confusion arises frequently with color images because it may be unclear whether a posted number refers to the bits per pixel or bits per channel. Using "bpp" as a suffix helps distinguish these two terms.
  4. 4. BIT DEPTH• Bits Per Pixel Number of Colors Available Common Name (s)• 1 2 Monochrome• 2 4 CGA• 4 16 EGA• 8 256 VGA• 16 65536 XGA, High Color• 24 16777216 SVGA, True Color• 32 16777216 + Transparency• 48 281 Trillion
  5. 5. BIT DEPTH• The human eye can only discern about 10 million different colors, so saving an image in any more than 24 bpp is excessive if the only intended purpose is for viewing.• On the other hand, images with more than 24 bpp are still quite useful since they hold up better under post-processing.
  6. 6. What is H.264/AVC?• H.264/Advanced Video Coding (AVC) is an industry standard for video compression. The H.264 standard is also known as MPEG-4 part 10 and is a successor to earlier standards such as MPEG -2 and MPEG -4.
  7. 7. What is H.264/AVC?• H.264 delivers MPEG – 4 quality with frame size up to four times greater. It can also provide MPEG -2 quality at reduced data rate, requiring as little as one third the original bandwidths.
  8. 8. APPLE ProRes4:2:2:(4)• Apple ProRes 422(HQ)•• This codec supports full-width, 4:2:2 video sources at 10 –bit pixel depths, while retaining its visually lossless characteristic through many generations of decoding and re-coding.•• 10-bit images can carry finer gradations of colour, thereby avoiding the banding artefacts that can occur in 8-bit images.
  9. 9. APPLE ProRes• Codec Colour Model Bit depth• ProRes 422 (proxy)YCbCr 10• ProRes 422 (LT)YCbCr 10• ProRes 422YCbCr 10• ProRes 422 (HQ)YCbCr 10• ProRes4444 RGB 12
  10. 10. AVID DNxHD• Avid DNxHD, which stands for "Digital Nonlinear Extensible High Definition", is a lossyhigh-definition videopost- productioncodec engineered for multi- generation compositing with reduced storage and bandwidth requirements.
  11. 11. AVID DNxHD• DNxHD is a video codec intended to be usable as both an intermediate format suitable for use while editing and as a presentation format.• DNxHD offers a choice of three user-selectable bit rates: 220 Mbit/s with a bit depth of 10 or 8 bits, and 145 or 36 Mbit/s with a bit depth of 8 bits.
  12. 12. 2K Vs 4K• The terms 2K and 4k originally referred to output of a film scanner. Each frame of 35mm film scanned gave you 4,000 red pixels, 4,000 green pixels, and 4,000 blue pixels in other word, 4K all round.• The high -end HD camera (true 4K0 have the same relationship on a full frame sensor, providing 4,096 photo sites (pixels) in an imagining area of 35mm film. This means you have 4,096 red, 4,096 green, and 4,096 blue photo sites captured, which is commonly referred to as 4:4:4.
  13. 13. 2K Vs 4K•• “If aspect ratio of a full 35mm film frame is 4x3 and you have 4,096 photo sites across the width and 3,000 along the height, then you have basically 4K by 3K. That’s 12 million of each of the green, red, and blue photo sites, or 36 million photo sites. That equates to what you’d get with a 4K film scan – a 36 megapixel scan.”
  14. 14. 2K Vs 4K• “ 4K doesn’t mean that just because you have 4,096 green photo sites and 2,048 red and blue that get interpolated through software, it’s a true 4K camera!• You can’t take an 8.3 million photo site sensor and create 36 million pixels out of that without interpolation and claim to have a 4K camera.”•
  15. 15. 2K Vs 4K• Making such claims is often referred to as marketing pixels. Mr Erland points out that RED isn’t the numbers with a similar technique and rely heavily on pushing the megapixels.• Not all 4K cameras in the market are truly 4K. Red One – its amazingly flexible and customisable camera, but it lacks the truth behind its 4K capabilities.
  16. 16. Dynamic Range• Dynamic Range is total range of tonal values recordable or usable. It’s noise tolerance dependant, but not scene dependent.•
  17. 17. Dynamic Range• How do we measure Dynamic Range?• Film a chart under controlled conditions – EV steps/fstops• Measure the pixel noise (RGBY)• Check the Dynamic response• Map the noise in fstop(EV) in each of RGB• Map the log of the exposure for each RGB•• EV=
  18. 18. Exposure Latitude• Exposure Latitude is by how much you can over and under expose and still have a usable image. It’s scene dependant.
  19. 19. REC 709• Is the output format for traditional television workflow. “Rec 709’ is short for the International Telecommunication Union’s ITU- R Recommendation BT.709. Rec 709 is the international standard for displaying images on video monitors, Look Up Tables (LuTs) are not necessary to show these images on monitors or to create dailies or editing proxies.
  20. 20. REC 709• Rec 709 images can be easily processed by most HD video post production gear in real time. While providing somewhat reduced choices in colour grading.
  21. 21. DCI P3• Is suited for DCI P3 (also known as SMPTE 431- 2) compliant displays. Those are primarily digital cinema projectors, but an increasing number of LCD displays support DCI P3 as well. DCI P3 has a similar tone mapping to REC 709 but a wider colour gamut that is designed to approximate the colour gamut of print film.••