TAV-DT doc

terranmon.txt

@@ -1609,8 +1609,8 @@ TSVM Advanced Video - Digital Tape (TAV-DT) Format
 Created by CuriousTorvald on 2025-12-01
 
 TAV-DT is an extension to TAV format that is intended as filesystem-independent packetised video stream
-with easy syncing (playback can start from the arbitrary position and decoder can easily sync up to the
-start of the packet)
+with easy syncing: playback can start from the arbitrary position and decoder can easily sync up to the
+start of the next packet
 
 # Video Format
     - Dimension: 720x480 for NTSC, 720x576 for PAL
@@ -1633,7 +1633,7 @@ start of the packet)
     uint8  Flags
         - bit 0 = interlaced
         - bit 1 = is NTSC framerate
-        - bit 4-7 = quality index
+        - bit 4-7 = quality index (0-15)
     int16  Reserved (zero-fill)
     uint32 Total packet size past header
     uint32 CRC-32 of 12-byte header
@@ -1641,6 +1641,34 @@ start of the packet)
     *      TAD packet (full 0x24 packet)
     *      TAV packet (full 0x10 or 0x12 packet)
 
+# How to sync to the stream
+    1. Find a sync pattern
+    2. Read remaining 8 bytes -> concatenate sync with what has been read
+    3. Calculate CRC-32 of concatenated 12 bytes
+    4. Read 4 bytes (stored CRC)
+    5. Check calculated CRC against stored CRC
+    6. If they match, sync to the stream; if not, find a next sync pattern
+
+# Quality Indices
+
+QIndex | Y,Co,Cg (true value) | TAD quality (max index)
+-----------------------------------------
+ 0 | 60,104,312 | 23
+ 1 | 44,88,248 | 31
+ 2 | 36,72,188 | 39
+ 3 | 28,56,136 | 47
+ 4 | 20,48,106 | 55
+ 5 | 16,40,80 | 63
+ 6 | 12,36,68 | 71
+ 7 | 10,32,58 | 79
+ 8 | 8,28,48 | 87
+ 9 | 6,24,38 | 95
+10 | 5,20,30 | 103
+11 | 4,16,22 | 111
+12 | 3,12,16 | 119
+13 | 2,8,10 | 123
+14 | 2,5,6 | 127
+15 | 1,2,2  | 127
 
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