feat: replace GPAC with FFmpeg for MP4 demuxing by DhanushVarma-2 · Pull Request #2170 · CCExtractor/ccextractor

DhanushVarma-2 · 2026-03-04T13:31:25Z

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Adds a Rust FFmpeg-based MP4 demuxer (rsmpeg) as a compile-time alternative to GPAC. Enabled with cmake -DWITH_FFMPEG=ON.

Supported: AVC/H.264, HEVC/H.265, CEA-608, CEA-708, tx3g, chapter extraction
Known gap: VobSub detected but not decoded
GPAC path: Unchanged, still the default

Note: mp4_ffmpeg_exports.rs shows as binary in the diff due to null-terminated C string literals for FFI — the file is clean UTF-8.

DhanushVarma-2 · 2026-03-06T06:32:55Z

The 9 Windows test failures (autoprogram, spupng, startcreditstext) are unrelated to MP4 demuxing — they involve subtitle encoding and credits detection, not the MP4 code path. These same tests pass on the Linux CI run. The Windows build itself was also delayed by a Chocolatey 503 outage when installing GPAC.

All 237 Linux tests pass, including the 3 MP4-specific tests. The Linux CI bot also notes this PR fixes 9 previously-broken tests that had never passed before.

cfsmp3 · 2026-03-07T18:04:07Z

Before going deep into this.

It would be a lot more readable to separate both implementations. Have process_mp4_ffmpeg and process_mp4_gpac functions, possibly in separate files, so we only need a few #ifdef guards.

Minimize the changes in the existing code (which already is not super well organized)...

Even (much better), do the ffmpeg part in rust. We don't want to add more C to the code - we really want to switch to rust.

DhanushVarma-2 · 2026-03-08T20:18:03Z

Before going deep into this.

It would be a lot more readable to separate both implementations. Have process_mp4_ffmpeg and process_mp4_gpac functions, possibly in separate files, so we only need a few #ifdef guards.

Minimize the changes in the existing code (which already is not super well organized)...

Even (much better), do the ffmpeg part in rust. We don't want to add more C to the code - we really want to switch to rust.

yeah sure.

Replace GPAC with FFmpeg for MP4 demuxing via a Rust implementation using rsmpeg. Supports AVC/H.264, HEVC/H.265, CEA-608, CEA-708, and tx3g subtitle tracks. Includes chapter extraction via ccxr_dumpchapters. VobSub tracks are detected but not yet supported. Selected at compile time via ENABLE_FFMPEG_MP4 / enable_mp4_ffmpeg Cargo feature.

- mp4_rust_bridge.c/.h: C-callable functions for AVC/HEVC/CC processing - ccx_gpac_types.h: compat defines for GF_4CC, GF_ISOM_SUBTYPE_C708, etc. - mp4.c: dispatch to Rust demuxer when ENABLE_FFMPEG_MP4 is set - ccextractor.c: iterate all input files in MP4 mode - Remove dead processmp4_ffmpeg/dumpchapters_ffmpeg declarations

- src/CMakeLists.txt: link swresample, re-add libs after ccx_rust for circular dependencies, --no-as-needed on Linux, ENABLE_HARDSUBX - lib_ccx/CMakeLists.txt: target_compile_definitions for ENABLE_HARDSUBX - rust/CMakeLists.txt: enable_mp4_ffmpeg Cargo feature

DhanushVarma-2 · 2026-03-10T12:48:29Z

@cfsmp3 Addressed all review feedback.
Rust FFmpeg demuxer supports AVC/H.264, HEVC/H.265, CEA-608/708, tx3g, and chapter extraction via rsmpeg. Build system fixes (ENABLE_HARDSUBX, link ordering, compat defines, swresample, bindgen allowlist), code cleanup (dead declarations, variable naming, match arm allocations), squashed to 3 commits. ccxr_dumpchapters is fully implemented shows as binary in diff due to FFI null terminators. VobSub detected but not decoded (known gap). Tested locally on MP4 files, all CI green.

DhanushVarma-2 · 2026-03-10T12:50:37Z

DhanushVarma-2 · 2026-04-02T18:37:46Z

@cfsmp3 can you review it.

cfsmp3 · 2026-04-04T22:00:56Z

Hi @DhanushVarma-2 — it looks like this branch was force-pushed and now only contains the MKV KATE extension fix (3 commits all with the same message). The original FFmpeg MP4 demuxer work is gone.

The KATE fix is already merged via #2250, so this PR currently has no diff against master.

Did you accidentally force-push the wrong branch? You'll need to restore the FFmpeg work or open a new PR. Let us know.

DhanushVarma-2 · 2026-04-04T22:19:34Z

HI @cfsmp3 Sorry about that , I accidentally force-pushed the wrong branch and overwrote the FFmpeg work. Restored it now and merged with upstream master. Should be good to review.

cfsmp3

Deep Review

Default build (no FFmpeg) — CLEAN

We built the PR without -DWITH_FFMPEG=ON and ran all 27 CI-flagged tests. Every single output file is byte-identical to master. The default GPAC path has zero regressions.

FFmpeg build — DOES NOT BUILD

We tried to build with -DWITH_FFMPEG=ON:

mkdir build_ffmpeg && cd build_ffmpeg
cmake ../src -DWITH_FFMPEG=ON
make -j$(nproc)

Error 1 (pre-existing, not your fault): ffmpeg_intgr.c:100 — av_find_best_stream incompatible pointer type. Our FFmpeg 7.x changed AVCodec** to const AVCodec**. We suppressed this with -Wno-incompatible-pointer-types to continue.

Error 2 (this PR): Linker fails with:

undefined reference to 'ccx_mp4_process_hevc_sample'

The symbol exists in mp4_rust_bridge.c → compiled into libccx.a. But libccx_rust.a (which needs it) comes LAST in the link order. The linker already consumed libccx.a and won't go back.

The existing codebase handles this with --undefined= flags (see --undefined=decode_vbi, --undefined=do_cb, --undefined=store_hdcc in the CMakeLists). You need the same for your new bridge symbols:

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--undefined=ccx_mp4_process_hevc_sample -Wl,--undefined=ccx_mp4_process_avc_sample")

Error 3 (this PR): lib_ccx/CMakeLists.txt replaces ENABLE_HARDSUBX with ENABLE_FFMPEG_MP4:

-  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_HARDSUBX")
+  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DENABLE_FFMPEG_MP4")

This means -DWITH_FFMPEG=ON no longer defines ENABLE_HARDSUBX, breaking hardsubx when FFmpeg is enabled. It should be added alongside, not replaced.

Code concerns

ccextractor.c changes the default MP4 processing loop — it now iterates over all input files inside the MP4 case. On master, only ctx->inputfile[ctx->current_file] is processed here. This changes behavior in the default (GPAC) path even without FFmpeg. Our tests didn't catch a regression (single-file MP4 tests pass), but this is a behavioral change that needs justification.
Unrelated cosmetic changes: ccx_decoders_isdb.c reformats the CLUT array (one value per line), teletext.rs reformats code from #2240. These don't belong in this PR — please remove them.
Test files: tests/popon_test.scc and tests/popon_test.srt — what are these for? Not mentioned in the PR description.

Summary

Since the FFmpeg build doesn't link, we couldn't test the actual new feature. Please fix:

Add --undefined linker flags for the bridge symbols
Keep ENABLE_HARDSUBX alongside ENABLE_FFMPEG_MP4
Remove unrelated cosmetic changes
Explain or remove the test files

Once it builds, we'll do a full test with MP4 samples comparing GPAC vs FFmpeg output.

- Add --undefined= linker flags for bridge symbols (ccx_mp4_process_avc_sample, ccx_mp4_process_hevc_sample, ccx_mp4_process_cc_packet, ccx_mp4_flush_tx3g) - Restore ENABLE_HARDSUBX alongside ENABLE_FFMPEG_MP4 in both CMakeLists - Guard MP4 multi-file loop with #ifdef ENABLE_FFMPEG_MP4 (GPAC path unchanged) - Revert unrelated cosmetic changes (isdb CLUT formatting, teletext.rs) - Remove unrelated test files (popon_test.scc/srt) - Revert .gitignore local dev additions

ccextractor-bot · 2026-04-05T13:41:18Z

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 395f9b3...:

Report Name	Tests Passed
Broken	9/13
CEA-708	1/14
DVB	3/7
DVD	3/3
DVR-MS	2/2
General	20/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	77/86
Teletext	20/21
WTV	13/13
XDS	31/34

Your PR breaks these cases:

ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b...
ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9...
ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc...
ccextractor --autoprogram --out=srt --latin1 b22260d065...
ccextractor --autoprogram --out=ttxt --latin1 --ucla 7aad20907e...
ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
ccextractor --autoprogram --out=ttxt --latin1 01509e4d27...
ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
ccextractor --out=spupng c83f765c66...
ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
ccextractor --autoprogram --out=ttxt --xds --latin1 --ucla 85058ad37e...
ccextractor --autoprogram --out=srt --latin1 --ucla b22260d065...
ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 7f41299cc7...

NOTE: The following tests have been failing on the master branch as well as the PR:

ccextractor --out=srt --latin1 --autoprogram 73d9313d64..., Last passed:
Test 8738
ccextractor --out=ttxt --latin1 001dd8cdf7..., Last passed:
Test 8738
ccextractor --out=srt --latin1 4d4e938ef6..., Last passed:
Test 8738
ccextractor --service 1 --out=txt --no-bom --no-rollup ea83ff7bcb..., Last passed:
Test 8738
ccextractor --service 1 --out=txt f17524b53f..., Last passed:
Test 8738
ccextractor --service 1 --out=txt 80848c45f8..., Last passed:
Test 8738
ccextractor --service 1 --out=txt --no-bom --no-rollup b5d6aad89f..., Last passed:
Test 8738
ccextractor --service 1[EUC-KR] --out=txt --no-rollup b5d6aad89f..., Last passed:
Test 8738
ccextractor --service 1 --out=srt da904de35d..., Last passed:
Test 8738
ccextractor --service 1 --out=sami da904de35d..., Last passed:
Test 8738
ccextractor --service 1 --out=ttxt da904de35d..., Last passed:
Test 8926
ccextractor --service 1[EUC-KR] b5d6aad89f..., Last passed:
Test 8738
ccextractor --service 1[EUC-KR] --no-rollup b5d6aad89f..., Last passed:
Test 8738
ccextractor --service all da904de35d..., Last passed:
Test 8738
ccextractor --service all[EUC-KR] b5d6aad89f..., Last passed:
Test 8738
ccextractor --service 1,2[UTF-8],3[EUC-KR],54 --out=txt da904de35d..., Last passed:
Test 8738
ccextractor --autoprogram --out=srt --latin1 d41b53b504..., Last passed:
Test 8738
ccextractor --stdout --quiet --no-fontcolor 79a51f3500..., Last passed:
Test 8738
ccextractor --stdout --quiet --no-fontcolor 767b546f96..., Last passed:
Test 8738
ccextractor --service 1 c83f765c66..., Last passed:
Test 8738
ccextractor --myth c83f765c66..., Last passed:
Test 8738
ccextractor --in=raw fb79021542..., Last passed:
Test 8738
ccextractor --mp4vidtrack 5df914ce77..., Last passed:
Test 8738
ccextractor --xmltv=3 --out=null 96efd279cf..., Last passed:
Test 8738
ccextractor --datapid 2310 --autoprogram --out=srt --latin1 e639e54550..., Last passed:
Test 8738

Congratulations: Merging this PR would fix the following tests:

ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.

ccextractor-bot · 2026-04-05T14:09:36Z

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit 395f9b3...:

Report Name	Tests Passed
Broken	9/13
CEA-708	1/14
DVB	4/7
DVD	3/3
DVR-MS	2/2
General	22/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	81/86
Teletext	20/21
WTV	13/13
XDS	31/34

Your PR breaks these cases:

ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b...
ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9...
ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc...
ccextractor --autoprogram --out=srt --latin1 b22260d065...
ccextractor --autoprogram --out=ttxt --latin1 --ucla 7aad20907e...
ccextractor --autoprogram --out=ttxt --latin1 01509e4d27...
ccextractor --autoprogram --out=ttxt --xds --latin1 --ucla 85058ad37e...
ccextractor --autoprogram --out=srt --latin1 --ucla b22260d065...
ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 7f41299cc7...

NOTE: The following tests have been failing on the master branch as well as the PR:

ccextractor --out=srt --latin1 --autoprogram 73d9313d64..., Last passed:
Test 8611
ccextractor --out=ttxt --latin1 001dd8cdf7..., Last passed:
Test 8611
ccextractor --out=srt --latin1 4d4e938ef6..., Last passed:
Test 8611
ccextractor --service 1 --out=txt --no-bom --no-rollup ea83ff7bcb..., Last passed:
Test 8611
ccextractor --service 1 --out=txt f17524b53f..., Last passed:
Test 8611
ccextractor --service 1 --out=txt 80848c45f8..., Last passed:
Test 8611
ccextractor --service 1 --out=txt --no-bom --no-rollup b5d6aad89f..., Last passed:
Test 8611
ccextractor --service 1[EUC-KR] --out=txt --no-rollup b5d6aad89f..., Last passed:
Test 8611
ccextractor --service 1 --out=srt da904de35d..., Last passed:
Test 8611
ccextractor --service 1 --out=sami da904de35d..., Last passed:
Test 8611
ccextractor --service 1 --out=ttxt da904de35d..., Last passed:
Test 8943
ccextractor --service 1[EUC-KR] b5d6aad89f..., Last passed:
Test 8611
ccextractor --service 1[EUC-KR] --no-rollup b5d6aad89f..., Last passed:
Test 8611
ccextractor --service all da904de35d..., Last passed:
Test 8611
ccextractor --service all[EUC-KR] b5d6aad89f..., Last passed:
Test 8611
ccextractor --service 1,2[UTF-8],3[EUC-KR],54 --out=txt da904de35d..., Last passed:
Test 8611
ccextractor --autoprogram --out=srt --latin1 d41b53b504..., Last passed:
Test 8611
ccextractor --stdout --quiet --no-fontcolor 79a51f3500..., Last passed:
Test 8611
ccextractor --stdout --quiet --no-fontcolor 767b546f96..., Last passed:
Test 8611
ccextractor --service 1 c83f765c66..., Last passed:
Test 8611
ccextractor --myth c83f765c66..., Last passed:
Test 8611
ccextractor --in=raw fb79021542..., Last passed:
Test 8611
ccextractor --mp4vidtrack 5df914ce77..., Last passed:
Test 8611
ccextractor --xmltv=3 --out=null 96efd279cf..., Last passed:
Test 8611
ccextractor --datapid 2310 --autoprogram --out=srt --latin1 e639e54550..., Last passed:
Test 8611

Congratulations: Merging this PR would fix the following tests:

ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed: Never
ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed: Never
ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed: Never
ccextractor --out=spupng c83f765c66..., Last passed: Never
ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.

DhanushVarma-2 changed the title ~~Feat/replace gpac with ffmpeg~~ feat: replace GPAC with FFmpeg for MP4 demuxing Mar 5, 2026

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch from 006130e to 4039844 Compare March 6, 2026 06:23

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch 13 times, most recently from 87f2178 to 9e95cd7 Compare March 7, 2026 06:59

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch from fd54002 to 513276d Compare March 10, 2026 10:48

Dhanush Varma added 2 commits March 10, 2026 16:32

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch from 513276d to aa75430 Compare March 10, 2026 11:03

This was referenced Mar 14, 2026

[IMPROVEMENT] feat(mp4): add FFmpeg/libavformat backend for MP4 demuxing #2191

Open

fix: add link_directories for tesseract/leptonica on macOS #2186

Merged

DhanushVarma-2 mentioned this pull request Mar 16, 2026

Fix/tx3g timestamp bug #2199

Open

10 tasks

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch 2 times, most recently from aa75430 to 814de82 Compare April 1, 2026 23:57

DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch from 814de82 to aa75430 Compare April 4, 2026 22:04

Dhanush Varma added 3 commits April 5, 2026 03:39

fix: add missing CHANGES.TXT entries from master

58d3c99

merge: sync with upstream master, resolve CHANGES.TXT conflict

ee1fd8b

style: apply rustfmt

d6289af

cfsmp3 requested changes Apr 5, 2026

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DhanushVarma-2 force-pushed the feat/replace-gpac-with-ffmpeg branch from 3b702c0 to e3e0a27 Compare April 5, 2026 13:06

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feat: replace GPAC with FFmpeg for MP4 demuxing #2170

feat: replace GPAC with FFmpeg for MP4 demuxing #2170
DhanushVarma-2 wants to merge 7 commits intoCCExtractor:masterfrom
DhanushVarma-2:feat/replace-gpac-with-ffmpeg

DhanushVarma-2 commented Mar 4, 2026 •

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Deep Review

Default build (no FFmpeg) — CLEAN

FFmpeg build — DOES NOT BUILD

Code concerns

Summary

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