Video Control

• Definition: Total number of pixels in an image (e.g. 1920×1080, 3840×2160). Often incorrectly referred to as “resolution” in English.
• Resolution: Pixel density per unit (e.g. DPI – dots per inch).

• Contrast Ratio: Ratio between brightest and darkest output (e.g. 2000:1, 4000:1). Higher values improve perceived image depth.

• Brightness: Measured in lumens.
  • ~1500 lumens: suitable for dark environments (home cinema)
  • >3000 lumens: recommended for environments with ambient light

• Definition (Format):
  • FHD (1920×1080) minimum standard
  • Higher than source → no benefit
  • Lower than source → visible quality loss

• Noise Level: Measured in dBA.
  • Typical acceptable range: 25–28 dBA
  • Manufacturer values may be optimistic

• Throw Ratio:
  • Formula: Throw Ratio = Distance / Image Width
  • Example: ratio 1.5 → 1m width at 1.5m distance
  • Defines projection size range depending on placement

• Overscan: Crops image edges and scales slightly beyond source resolution

• NDI Monitor:
  • Provides preview (low-resolution proxy)
  • Not suitable for full-quality signal transmission

• LPMT (Linux Projection Mapping Tool)
• Millumin
• Resolume Arena
• MadMapper
• QLab
• Modulo Kinetic / Modulo Player
• mplayer (video playback)

ffmpeg -i input.mp4 -vcodec prores -acodec copy output.mov

ffmpeg -i input-video.mp4 -vf "transpose=1" output-video.mp4

• 0 → 90° CCW + flip
• 1 → 90° CW
• 2 → 90° CCW
• 3 → 90° CW + flip

• CRF range: 0 (lossless) → 51 (worst)
• Typical values: 15–20

To create a 1min clip starting 1min into the video:

ffmpeg -i input-video.mp4 -c:v libx264 -crf 15 -c:a aac -ss=60 -t=60 output-video.mp4

$ffmpeg -codecs
 
D..... = Decoding supported
.E.... = Encoding supported
..V... = Video codec
..A... = Audio codec
..S... = Subtitle codec
...I.. = Intra frame-only codec
....L. = Lossy compression
.....S = Lossless compression
 
$ffmpeg -encoders
 
V..... = Video
A..... = Audio
S..... = Subtitle
.F.... = Frame-level multithreading
..S... = Slice-level multithreading
...X.. = Codec is experimental
....B. = Supports draw_horiz_band
.....D = Supports direct rendering method 1
 
$ffmpeg -h encoder=libx264 //list all options on encoder

• Defines precision of color values
• 8-bit → 256 levels per channel
• 10-bit → 1024 levels per channel

• Benefits of 10-bit:
  • Smoother gradients
  • Reduced banding
  • Better fades (especially on LED displays)

• Important:
  • Bit depth does not define color range
  • It improves how smoothly colors transition

• Rec.709
  • Standard HD color space
  • Used in most video and LED workflows
  • Predictable and widely supported

• Rec.2020
  • Wider color gamut (UHD / HDR)
  • Enables more saturated colors
  • Requires full pipeline support (rare in real-time systems)

• Key distinction:
  • Color space = range of colors available
  • Bit depth = precision within that range

• Defines how brightness is encoded

• Common values:
  • Gamma 2.4 → video standard (recommended baseline)
  • Gamma 2.2 / sRGB → desktop environments
  • PQ / HLG → HDR workflows

• In real-time playback systems:
  • Gamma is often assumed, not explicitly managed

• Most pipelines are effectively Rec.709-based
• Color management is usually not enforced
• Wide gamut (Rec.2020) only useful if:
  • Playback engine supports it
  • Signal chain preserves it
  • Display can reproduce it

• Otherwise:
  • Colors may be clipped or altered

• Use a 10-bit grayscale gradient test pattern

• Interpretation:
  • Smooth gradient → full pipeline is 10-bit
  • Banding → limitation exists in:
    • media encoding
    • GPU output
    • signal chain (HDMI/SDI)
    • processor
    • display

• sRGB:
  • Close to Rec.709 but not identical
  • Not relevant in video signal pipelines

• HDR (Rec.2020 + PQ/HLG):
  • Requires full end-to-end support
  • Not guaranteed in real-time playback systems

• https://www.lesnumeriques.com/photo/definition-et-resolution-quelle-difference-pu102319.html