====== Video Control ======

===== Projectors =====

==== Terminology ====

  * **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).

==== Key Specifications ====

  * **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

==== Image Processing Options ====

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

----

===== NDI =====

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

----

===== Software =====

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

----

===== FFmpeg =====

=== Re-encode into Apple ProRes ===

<code bash>
ffmpeg -i input.mp4 -vcodec prores -acodec copy output.mov
</code>

=== Rotate Video ===

<code bash>
ffmpeg -i input-video.mp4 -vf "transpose=1" output-video.mp4
</code>

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

=== Control Quality (CRF) ===

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

=== Trim Video ===

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

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


=== ffmpeg commands ===


<code bash>
$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
</code>

----

===== Signal Formats & Bitrates =====


{{regie:video_formats_bitrates.png?500}}

----

===== Color Pipeline (Bit Depth, Color Space, Gamma) =====

==== Bit Depth ====

  * 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**

----

==== Color Spaces ====

  * **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**

----

==== Gamma / Transfer Function ====

  * 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

----

==== Practical Notes (Real-Time & LED Workflows) ====

  * 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

----

==== Validation (10-bit Workflow) ====

  * 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

----

==== Notes ====

  * **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

----