From 214ff6911e150a43d06ffa1bb2e8516b21cfc122 Mon Sep 17 00:00:00 2001
From: metamuffin <metamuffin@disroot.org>
Date: Sun, 21 May 2023 11:14:57 +0200
Subject: spec

---
 bv1/spec.md | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 bv1/spec.md

diff --git a/bv1/spec.md b/bv1/spec.md
new file mode 100644
index 0000000..ca30a39
--- /dev/null
+++ b/bv1/spec.md
@@ -0,0 +1,45 @@
+# BOMedia Video 1
+
+The codec compresses image sequences by avoiding redundancies by reusing parts
+of previous frames. A frame is one block that is then subdivided further as
+needed.
+
+## Literal-Block
+
+Stores the pixels' RGB values as is.
+
+## Split-Block
+
+Delegates to two sub-blocks. The block is split orthorgonally on the longest
+axis. If needed, the left/top block is rounded down and the right/bottom rounded
+up.
+
+## Reference-Block
+
+Indicates that parts of the last frame are reused. The data reused is at the
+position of this block in the last frame with the translation added.
+
+## File format
+
+- magic bytes: `5e b1 c3 08`
+- resolution: _`u16, u16`_
+- frame count: _`u64`_
+- frames (repeated [frame count]-times): Frame (see below)
+
+## Frame format
+
+- block kind: _`u8` (see tags below)_
+- block: _one of the following_
+  - 0 **Split-Block**
+    - sub-blocks: _`[block; 2]` (see above)_
+  - 1 **Literal-Block**
+    - pixels: _`[[u8; 3]; (inferred)]`_ (stored line-by-line)
+  - 2 **Reference-Block**
+    - position_offset: _`[i8; 2]`_
+    - color_offset: _`[i16; 3]`_
+
+### Data Types
+
+- _`u<n>`_: unsigned n-bit integer (little-endian)
+- _`i<n>`_: signed n-bit integer using twos-complement (little-endian)
+- _`[<T>; <N>]`_: Array of T with length N
-- 
cgit v1.2.3-70-g09d2