[PR #1782] feat(rust): Add persistent DtvccRust context for CEA-708 decoder (Pha… #2510

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claunia · 2026-01-29T17:22:31Z

claunia commented

2026-01-29 17:22:31 +00:00

Original Pull Request: https://github.com/CCExtractor/ccextractor/pull/1782

State: closed
Merged: Yes

Fix CEA-708 Decoder State Persistence (Issue #1499)

This PR fully implements the fix for issue #1499. The Rust CEA-708 decoder was creating a new Dtvcc struct on every call to ccxr_process_cc_data(), causing all state to be reset and breaking stateful caption processing.

Based on #1618, which doesn't merge cleanly and contains implementations that differ from current code.

Changes by Phase

Phase 1: Rust Core

Added DtvccRust struct in decoder/mod.rs that owns its decoder state
Added CCX_DTVCC_MAX_SERVICES constant (63)
Added FFI functions in lib.rs:
- ccxr_dtvcc_init(): Create persistent context
- ccxr_dtvcc_free(): Free context and all owned memory
- ccxr_dtvcc_set_encoder(): Set encoder (not available at init)
- ccxr_dtvcc_process_data(): Process CC data on persistent context
- ccxr_flush_active_decoders(): Flush all active decoders
- ccxr_dtvcc_is_active(): Check if context is active
Used heap allocation for large structs to avoid stack overflow
Added unit tests for DtvccRust

Phase 2: C Headers

Added void *dtvcc_rust field to lib_cc_decode struct in ccx_decoders_structs.h
Added extern declarations in ccx_dtvcc.h for init/free/process_data/is_active
Added extern declaration in lib_ccx.h for ccxr_dtvcc_set_encoder
Added extern declaration in ccx_decoders_common.h for ccxr_flush_active_decoders

Phase 3: C Implementation

Modified ccx_decoders_common.c:
- init_cc_decode(): Use ccxr_dtvcc_init() when Rust enabled
- dinit_cc_decode(): Use ccxr_dtvcc_free() when Rust enabled
- flush_cc_decode(): Use ccxr_flush_active_decoders() when Rust enabled
Modified general_loop.c: Set encoder via ccxr_dtvcc_set_encoder() at 3 locations
Modified mp4.c: Use ccxr_dtvcc_set_encoder() and ccxr_dtvcc_process_data()
All changes guarded with #ifndef DISABLE_RUST

Phase 4: Bug Fix & Testing

Fixed ccxr_process_cc_data() to use persistent DtvccRust from dec_ctx.dtvcc_rust instead of creating new Dtvcc from dec_ctx.dtvcc (which is NULL when Rust enabled)
Added do_cb_dtvcc_rust() function for processing with DtvccRust

Testing

Automated Tests

All 269 Rust unit tests pass
Cargo clippy passes with no errors
CI builds pass on Linux, Mac, Windows

Manual Testing

Tested with CEA-708 transport stream file (ANDE.ts):
- ~10 minute file with 25,598 DTVCC packets
- Successfully extracted 21KB of captions
- No crashes, proper SRT output with timestamps
Tested with CEA-708 program stream file:
- Processed without crashes
- Verified state persistence across calls

Files Modified

File	Changes
`src/rust/src/decoder/mod.rs`	Added `DtvccRust` struct and methods
`src/rust/src/lib.rs`	Added FFI functions, fixed `ccxr_process_cc_data`
`src/lib_ccx/ccx_decoders_structs.h`	Added `dtvcc_rust` field
`src/lib_ccx/ccx_dtvcc.h`	Added extern declarations
`src/lib_ccx/lib_ccx.h`	Added `ccxr_dtvcc_set_encoder` declaration
`src/lib_ccx/ccx_decoders_common.h`	Added `ccxr_flush_active_decoders` declaration
`src/lib_ccx/ccx_decoders_common.c`	Use Rust init/free/flush
`src/lib_ccx/general_loop.c`	Set encoder via Rust FFI
`src/lib_ccx/mp4.c`	Use Rust FFI for encoder and processing

Fixes: #1499

**Original Pull Request:** https://github.com/CCExtractor/ccextractor/pull/1782 **State:** closed **Merged:** Yes --- ## Fix CEA-708 Decoder State Persistence (Issue #1499) This PR fully implements the fix for issue #1499. The Rust CEA-708 decoder was creating a new `Dtvcc` struct on every call to `ccxr_process_cc_data()`, causing all state to be reset and breaking stateful caption processing. Based on #1618, which doesn't merge cleanly and contains implementations that differ from current code. ## Changes by Phase ### Phase 1: Rust Core - Added `DtvccRust` struct in `decoder/mod.rs` that owns its decoder state - Added `CCX_DTVCC_MAX_SERVICES` constant (63) - Added FFI functions in `lib.rs`: - `ccxr_dtvcc_init()`: Create persistent context - `ccxr_dtvcc_free()`: Free context and all owned memory - `ccxr_dtvcc_set_encoder()`: Set encoder (not available at init) - `ccxr_dtvcc_process_data()`: Process CC data on persistent context - `ccxr_flush_active_decoders()`: Flush all active decoders - `ccxr_dtvcc_is_active()`: Check if context is active - Used heap allocation for large structs to avoid stack overflow - Added unit tests for `DtvccRust` ### Phase 2: C Headers - Added `void *dtvcc_rust` field to `lib_cc_decode` struct in `ccx_decoders_structs.h` - Added extern declarations in `ccx_dtvcc.h` for init/free/process_data/is_active - Added extern declaration in `lib_ccx.h` for `ccxr_dtvcc_set_encoder` - Added extern declaration in `ccx_decoders_common.h` for `ccxr_flush_active_decoders` ### Phase 3: C Implementation - Modified `ccx_decoders_common.c`: - `init_cc_decode()`: Use `ccxr_dtvcc_init()` when Rust enabled - `dinit_cc_decode()`: Use `ccxr_dtvcc_free()` when Rust enabled - `flush_cc_decode()`: Use `ccxr_flush_active_decoders()` when Rust enabled - Modified `general_loop.c`: Set encoder via `ccxr_dtvcc_set_encoder()` at 3 locations - Modified `mp4.c`: Use `ccxr_dtvcc_set_encoder()` and `ccxr_dtvcc_process_data()` - All changes guarded with `#ifndef DISABLE_RUST` ### Phase 4: Bug Fix & Testing - Fixed `ccxr_process_cc_data()` to use persistent `DtvccRust` from `dec_ctx.dtvcc_rust` instead of creating new `Dtvcc` from `dec_ctx.dtvcc` (which is NULL when Rust enabled) - Added `do_cb_dtvcc_rust()` function for processing with `DtvccRust` ## Testing ### Automated Tests - All 269 Rust unit tests pass - Cargo clippy passes with no errors - CI builds pass on Linux, Mac, Windows ### Manual Testing - Tested with CEA-708 transport stream file (ANDE.ts): - ~10 minute file with 25,598 DTVCC packets - Successfully extracted 21KB of captions - No crashes, proper SRT output with timestamps - Tested with CEA-708 program stream file: - Processed without crashes - Verified state persistence across calls ## Files Modified | File | Changes | |------|---------| | `src/rust/src/decoder/mod.rs` | Added `DtvccRust` struct and methods | | `src/rust/src/lib.rs` | Added FFI functions, fixed `ccxr_process_cc_data` | | `src/lib_ccx/ccx_decoders_structs.h` | Added `dtvcc_rust` field | | `src/lib_ccx/ccx_dtvcc.h` | Added extern declarations | | `src/lib_ccx/lib_ccx.h` | Added `ccxr_dtvcc_set_encoder` declaration | | `src/lib_ccx/ccx_decoders_common.h` | Added `ccxr_flush_active_decoders` declaration | | `src/lib_ccx/ccx_decoders_common.c` | Use Rust init/free/flush | | `src/lib_ccx/general_loop.c` | Set encoder via Rust FFI | | `src/lib_ccx/mp4.c` | Use Rust FFI for encoder and processing | Fixes: #1499

claunia added the pull-request label 2026-01-29 17:22:31 +00:00

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Reference: starred/ccextractor#2510