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TAV-DT: more format revision

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minjaesong
2025-12-17 03:20:19 +09:00
parent ca037c8e74
commit e893ca2df5
3 changed files with 278 additions and 100 deletions
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23
terranmon.txt
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@@ -1649,25 +1649,30 @@ start of the next packet
uint32 Total packet size (sum of TAD packet and TAV packet size)
uint64 Timecode in nanoseconds
uint32 Offset to video packet
uint32 CRC-32 of [sync pattern + framerate + flags + reserved + total packet size + timecode + offset]
<packet header end; encoded with rate 1/2 LDPC>
uint32 Reserved (zero-fill)
uint32 CRC-32 of [sync pattern + above]
<packet header end; encoded with rate 256/512 LDPC>
bytes TAD with forward error correction
<TAD header start>
uint16 Sample Count
uint8 Quantiser Bits
uint16 Reserved (zero-fill)
uint32 Compressed Size
uint24 Reed-Solomon Block Count
<TAD chunk header end; encoded with rate 1/2 LDPC>
uint32 CRC-32 of above
<TAD chunk header end; encoded with rate 128/256 LDPC>
<Reed-Solomon (255,223) block start>
bytes TAD (EZBC, no Zstd)
bytes Parity for TAD
<Reed-Solomon (255,223) block end>
bytes TAV with forward error correction
<TAV header start>
uint32 TAV header sync pattern (0xA3F7C91E)
uint8 GOP Size (number of frames in this GOP)
uint32 Compressed Size
uint24 Reed-Solomon Block Count
<TAV header end; encoded with rate 1/2 LDPC>
uint32 CRC-32 of above
<TAV header end; encoded with rate 128/256 LDPC>
<Reed-Solomon (255,223) block start>
bytes TAV (EZBC, no Zstd)
bytes Parity for TAV
@@ -1679,6 +1684,8 @@ start of the next packet
Q2. What to do when payload is smaller than RS block capacity?
A2. Fill with zero. It shouldn't affect Zstd, and compressed size is already specified, so they complement each other.
When decoding, reserved areas must be filled with zero before the actual decoding.
# How to sync to the stream
1. Find a sync pattern
2. Read remaining 8 bytes -> concatenate sync with what has been read
@@ -1703,7 +1710,13 @@ On the stream position where the sync pattern is supposed to be:
### Stage 2
1. Further substitute the framerate, flags, timecode to the last known value (as these values rarely change mid-stream; timecode must be incremented appropriately. e.g. FPS=16, last known timecode=5.0, packets missed so far=4, then assumed timecode is 5.0 + 4 + 1 = 10.0)
2. Re-calculate CRC. If match, sync. If not, soft sync recovery is failed, and discard the packet
2. Re-calculate CRC. If match, sync. If not, head to the next stage
### Stage 3 (mostly throwaway efforts)
1. Search for 0xA3F7C91E or next sync pattern
2. If 0xA3F7C91E is found, try to decode the subpacket by verifying header with CRC; if next sync pattern is found, sync to that packet.
3. If successful, sync. If not, soft sync recovery is failed, and discard the packet
Note: If CRC is unmatched, the packet MUST be discarded, as the header content cannot be trusted if all soft recovery stages have failed