feat: add Rust FFmpeg MP4 demuxer with compile-time switch

  Replace GPAC-based MP4 demuxer with FFmpeg-based implementation in Rust
  using rsmpeg, activated via -DWITH_FFMPEG=ON. GPAC path remains default
  and untouched when FFmpeg is not enabled.

  Architecture:
  - Rust core (demuxer/mp4.rs): opens MP4 via rsmpeg, classifies tracks,
    dispatches packets to C bridge functions
  - FFI exports (mp4_ffmpeg_exports.rs): ccxr_processmp4/ccxr_dumpchapters
    callable from C
  - C bridge (mp4_rust_bridge.c): flat FFI-safe wrappers around existing
    do_NAL, process608, dtvcc_process_data, store_hdcc, encode_sub

  Supports AVC/H.264, HEVC/H.265, CEA-608, CEA-708, and tx3g tracks.
  Parses SPS/PPS/VPS from extradata for proper caption extraction.

  Build: cmake -DWITH_FFMPEG=ON -DWITH_OCR=ON -DWITH_HARDSUBX=ON ../src
  CI: fixed Linux cmake_ffmpeg_mp4 job, added macOS cmake_ffmpeg_mp4 job

Author: gaurav-dev02

.github/workflows/build_linux.yml

@@ -84,7 +84,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Install dependencies
-      run: sudo apt update && sudo apt-get install libgpac-dev libavcodec-dev libavformat-dev libavutil-dev libswresample-dev libswscale-dev
+      run: sudo apt update && sudo apt-get install libgpac-dev libtesseract-dev libleptonica-dev libavcodec-dev libavformat-dev libavutil-dev libavfilter-dev libswresample-dev libswscale-dev
     - uses: actions/checkout@v6
     - name: cmake (default GPAC build)
       run: mkdir build && cd build && cmake ../src
@@ -94,7 +94,7 @@ jobs:
     - name: Display version information (GPAC build)
       run: ./build/ccextractor --version
     - name: cmake (FFmpeg MP4 build)
-      run: mkdir build_ffmpeg && cd build_ffmpeg && cmake -DUSE_FFMPEG_MP4=ON ../src
+      run: mkdir build_ffmpeg && cd build_ffmpeg && cmake -DWITH_FFMPEG=ON -DWITH_OCR=ON -DWITH_HARDSUBX=ON ../src
     - name: build (FFmpeg MP4 build)
       run: make -j$(nproc)
       working-directory: build_ffmpeg

.github/workflows/build_mac.yml

@@ -107,6 +107,21 @@ jobs:
       working-directory: build
     - name: Display version information
       run: ./build/ccextractor --version
+  cmake_ffmpeg_mp4:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@v6
+    - name: Install dependencies
+      run: brew install pkg-config gpac ffmpeg tesseract leptonica
+    - name: cmake (FFmpeg MP4 build)
+      run: |
+        mkdir build && cd build
+        cmake -DWITH_FFMPEG=ON -DWITH_OCR=ON -DWITH_HARDSUBX=ON ../src
+    - name: build
+      run: make -j$(nproc)
+      working-directory: build
+    - name: Display version information
+      run: ./build/ccextractor --version
   build_shell_hardsubx:
     # Test build.command with -hardsubx flag (burned-in subtitle extraction)
     runs-on: macos-latest

src/CMakeLists.txt

@@ -196,6 +196,13 @@ if (PKG_CONFIG_FOUND AND WITH_FFMPEG)
 
   set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_FFMPEG")
   set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_HARDSUBX")
+  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_FFMPEG_MP4")
+
+  pkg_check_modules (SWRESAMPLE libswresample)
+  if (SWRESAMPLE_FOUND)
+    set (EXTRA_LIBS ${EXTRA_LIBS} ${SWRESAMPLE_LIBRARIES})
+    set (EXTRA_INCLUDES ${EXTRA_INCLUDES} ${SWRESAMPLE_INCLUDE_DIRS})
+  endif()
 endif (PKG_CONFIG_FOUND AND WITH_FFMPEG)
 
 ########################################################

src/ccextractor.c

@@ -222,12 +222,23 @@ int start_ccx()
 					ret = tmp;
 				break;
 			case CCX_SM_MP4:
-				mprint("\rAnalyzing data with GPAC (MP4 library)\n");
-				close_input_file(ctx);	     // No need to have it open. GPAC will do it for us
-				if (ctx->current_file == -1) // We don't have a file to open, must be stdin, and GPAC is incompatible with stdin
+				close_input_file(ctx);	     // No need to have it open. The demuxer will do it for us
+				if (ctx->current_file == -1) // We don't have a file to open, must be stdin
 				{
 					fatal(EXIT_INCOMPATIBLE_PARAMETERS, "MP4 requires an actual file, it's not possible to read from a stream, including stdin.\n");
 				}
+#ifdef ENABLE_FFMPEG_MP4
+				mprint("\rAnalyzing data with FFmpeg (MP4 demuxer)\n");
+				if (ccx_options.extract_chapters)
+				{
+					tmp = ccxr_dumpchapters(ctx, ctx->inputfile[ctx->current_file]);
+				}
+				else
+				{
+					tmp = ccxr_processmp4(ctx, ctx->inputfile[ctx->current_file]);
+				}
+#else
+				mprint("\rAnalyzing data with GPAC (MP4 library)\n");
 				if (ccx_options.extract_chapters)
 				{
 					tmp = dumpchapters(ctx, &ctx->mp4_cfg, ctx->inputfile[ctx->current_file]);
@@ -236,6 +247,7 @@ int start_ccx()
 				{
 					tmp = processmp4(ctx, &ctx->mp4_cfg, ctx->inputfile[ctx->current_file]);
 				}
+#endif
 				if (ccx_options.print_file_reports)
 					print_file_report(ctx);
 				if (!ret)

src/lib_ccx/CMakeLists.txt

@@ -39,6 +39,7 @@ if (WITH_FFMPEG)
 
   set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_FFMPEG")
   set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_HARDSUBX")
+  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_FFMPEG_MP4")
 endif (WITH_FFMPEG)
 
 if (WITH_OCR)

src/lib_ccx/ccx_gpac_types.h

@@ -0,0 +1,44 @@
+/*
+ * Minimal GPAC-compatible type definitions for the FFmpeg MP4 bridge.
+ * When ENABLE_FFMPEG_MP4 is defined and GPAC headers may not be available,
+ * these provide the subset of GPAC types needed by the C bridge functions.
+ */
+#ifndef CCX_GPAC_TYPES_H
+#define CCX_GPAC_TYPES_H
+
+#include <stdint.h>
+
+#ifndef GPAC_VERSION_MAJOR
+/* Only define these if real GPAC headers are not included */
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+typedef int32_t s32;
+
+#ifndef GF_4CC
+#define GF_4CC(a,b,c,d) ((((u32)a)<<24)|(((u32)b)<<16)|(((u32)c)<<8)|((u32)d))
+#endif
+
+/* Minimal GF_AVCConfig - only fields used by process_avc_sample */
+typedef struct {
+    u8 nal_unit_size;
+} GF_AVCConfig_Minimal;
+
+/* Minimal GF_HEVCConfig - only fields used by process_hevc_sample */
+typedef struct {
+    u8 nal_unit_size;
+} GF_HEVCConfig_Minimal;
+
+/* Minimal GF_ISOSample - only fields used by process_*_sample */
+typedef struct {
+    u32 dataLength;
+    char *data;
+    u64 DTS;
+    u32 CTS_Offset;
+} GF_ISOSample_Minimal;
+
+#endif /* GPAC_VERSION_MAJOR */
+
+#endif /* CCX_GPAC_TYPES_H */

src/lib_ccx/ccx_mp4.h

@@ -3,4 +3,12 @@
 
 int processmp4(struct lib_ccx_ctx *ctx, struct ccx_s_mp4Cfg *cfg, char *file);
 int dumpchapters(struct lib_ccx_ctx *ctx, struct ccx_s_mp4Cfg *cfg, char *file);
+unsigned char *ccdp_find_data(unsigned char *ccdp_atom_content, unsigned int len, unsigned int *cc_count);
+
+#ifdef ENABLE_FFMPEG_MP4
+/* Rust FFmpeg MP4 demuxer entry points */
+int ccxr_processmp4(struct lib_ccx_ctx *ctx, const char *file);
+int ccxr_dumpchapters(struct lib_ccx_ctx *ctx, const char *file);
+#endif
+
 #endif