Today I tried to build this project because I am using MacOS and the opencv-linking seemed to be broken. using cargo was easy (even though I am not that familiar with rust but finding out that the page needed to be built using yarn was quite something.

Some building documentation would be nice. (Some lines on where to use cargo build and yarn install && yarn build).

When trying to build and run on macos/linux I get the following error: thread 'main' panicked at 'attempt to subtract with overflow', crates/app/src/db.rs:180:31 I seemed to have already fixed the issue by modifying the db.rs file (after some googling I found out that this issue seems to accur, when you try to subtract 1 from 0)

diff --git a/crates/app/src/db.rs b/crates/app/src/db.rs
index 2478358..da7e2b1 100644
--- a/crates/app/src/db.rs
+++ b/crates/app/src/db.rs
@@ -177,7 +177,12 @@ impl<'a> Db<'a, TransactionMarker> {
             let pdf_hash = matching.image.map(|p| p.pdf_hash);
             let video_ms = matching.video_time.as_millis() as u32;
             let page_nr = matching.image.map(|p| p.page_nr as u32).unwrap_or(0);
-            let page_offset = page_nr - 1;
+            let page_offset;
+            if page_nr > 0 {
+                page_offset = page_nr - 1;
+            } else {
+                page_offset = 0;
+            }
             sqlx::query!(
                 "INSERT INTO videos_mapping(video_id, video_ms, pdf_hash, page) VALUES (?, ?, ?, ?)",
                 video_id,

Hi, I was looking for such software... If I am right, the slide matching can be done by a background processing application that return a JSON slide timing output to perform a bisect. This application can be written in C++, or even in Python since most of the job in done in OpenCV. MuPDF could be used to render the PDF page as a better alternative to Poppler. Then the display can be done by a web application that connect the video current time to PDF.js For sure such application is trivial to build in Qt QML. Well, I don't understand why you want to use Rust for everything.

On some Videos/pdf-combinations I get this error on MacOS while slideo is processing frames: (This only happens on certain frames and always on the same ones)

Then, after completely processing the video the webserver isn't started and when the pdf is opened manually by executing slideo file.pdf the pdf doesn't have any timestamps.

Full Backtrace:

thread '<unnamed>' panicked at 'called `Option::unwrap()` on a `None` value', /Users/lukas/Documents/slideo/crates/matching-opencv/src/lib.rs:371:69
stack backtrace:
   0:        0x10bcf78de - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h04abbaabf148650a
   1:        0x10bd3a98e - core::fmt::write::h14dac7cadec1cc70
   2:        0x10bcf708a - std::io::Write::write_fmt::hfaf2e10dfdcc61d8
   3:        0x10bd159e9 - std::panicking::default_hook::{{closure}}::h350fee0bf60f2674
   4:        0x10bd1555b - std::panicking::default_hook::h0b4e3bc46e6dcb8d
   5:        0x10bd15f7a - std::panicking::rust_panic_with_hook::h8cdc0a575f4a5a7b
   6:        0x10bcf8079 - std::panicking::begin_panic_handler::{{closure}}::h7a7b30fd1c313876
   7:        0x10bcf7a28 - std::sys_common::backtrace::__rust_end_short_backtrace::h2e099be83c81509d
   8:        0x10bd15af3 - _rust_begin_unwind
   9:        0x10bd473ef - core::panicking::panic_fmt::h4f63e4f6b62b650b
  10:        0x10bd47347 - core::panicking::panic::hb3c06f51e2e58141
  11:        0x10afa59a9 - core::option::Option<T>::unwrap::hb3706e21acd48f48
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/core/src/option.rs:386:21
  12:        0x10b105cb2 - matching_opencv::OpenCVVideoMatcherTask<I>::match_images_with_frame::{{closure}}::h6ac2efa761b34801
                               at /Users/lukas/Documents/slideo/crates/matching-opencv/src/lib.rs:371:47
  13:        0x10b0e2242 - alloc::slice::<impl [T]>::sort_by::{{closure}}::h4e32b55bca503dbc
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/alloc/src/slice.rs:311:33
  14:        0x10b0e0f62 - alloc::slice::insert_head::h22f59d896a4d25dc
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/alloc/src/slice.rs:840:24
  15:        0x10b0dd846 - alloc::slice::merge_sort::h50931d4fdb6fb654
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/alloc/src/slice.rs:1047:17
  16:        0x10b108531 - alloc::slice::<impl [T]>::sort_by::h296008c9323b96d6
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/alloc/src/slice.rs:311:9
  17:        0x10b1054cb - matching_opencv::OpenCVVideoMatcherTask<I>::match_images_with_frame::h2e9e32b4065f5258
                               at /Users/lukas/Documents/slideo/crates/matching-opencv/src/lib.rs:371:13
  18:        0x10b103ea8 - <matching_opencv::OpenCVVideoMatcherTask<I> as matching::VideoMatcherTask<I>>::process::{{closure}}::{{closure}}::h69525bcbd55619bc
                               at /Users/lukas/Documents/slideo/crates/matching-opencv/src/lib.rs:214:36
  19:        0x10b0239d6 - rayon_core::scope::ScopeFifo::spawn_fifo::{{closure}}::{{closure}}::h14d50d9aafa378d9
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/scope/mod.rs:495:47
  20:        0x10b116d31 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h82d2844e73051b6f
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panic.rs:344:9
  21:        0x10b00bf95 - std::panicking::try::do_call::h43dc9bd5aa331631
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panicking.rs:379:40
  22:        0x10b00de3d - ___rust_try
  23:        0x10b00a231 - std::panicking::try::h93de8b23b179aca6
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panicking.rs:343:19
  24:        0x10b1177e1 - std::panic::catch_unwind::haa922ddd00603855
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panic.rs:431:14
  25:        0x10b15dd11 - rayon_core::unwind::halt_unwinding::hb8f4d4b69b63ef43
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/unwind.rs:17:5
  26:        0x10b023491 - rayon_core::scope::ScopeBase::execute_job_closure::h2b938e0ac14a5ca7
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/scope/mod.rs:561:15
  27:        0x10b023425 - rayon_core::scope::ScopeBase::execute_job::h8bcba628953f50d9
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/scope/mod.rs:549:29
  28:        0x10b02397d - rayon_core::scope::ScopeFifo::spawn_fifo::{{closure}}::hcd25299f0e0d3306
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/scope/mod.rs:495:17
  29:        0x10b0d35dd - <rayon_core::job::HeapJob<BODY> as rayon_core::job::Job>::execute::ha6e2be962215648e
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/job.rs:167:9
  30:        0x10b7532b5 - rayon_core::job::JobRef::execute::h9905210a4b77f273
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/job.rs:59:9
  31:        0x10b7533c8 - <rayon_core::job::JobFifo as rayon_core::job::Job>::execute::ha3c023d7050ec006
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/job.rs:211:50
  32:        0x10b7532b5 - rayon_core::job::JobRef::execute::h9905210a4b77f273
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/job.rs:59:9
  33:        0x10b728e3d - rayon_core::registry::WorkerThread::execute::h52bdcf205839c2ce
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:753:9
  34:        0x10bd41548 - rayon_core::registry::WorkerThread::wait_until_cold::h856430079a15650f
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:730:17
  35:        0x10b728c78 - rayon_core::registry::WorkerThread::wait_until::ha9dbb2d013ef9bc2
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:704:13
  36:        0x10b7295f3 - rayon_core::registry::main_loop::h2141c7566ae34282
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:837:5
  37:        0x10b7264c0 - rayon_core::registry::ThreadBuilder::run::hccf2fa9a1df253e9
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:56:18
  38:        0x10b7269d1 - <rayon_core::registry::DefaultSpawn as rayon_core::registry::ThreadSpawn>::spawn::{{closure}}::h70f699ea15ed07e4
                               at /Users/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.0/src/registry.rs:101:20
  39:        0x10b72f860 - std::sys_common::backtrace::__rust_begin_short_backtrace::hfdc1dafbe1be5b5f
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/sys_common/backtrace.rs:125:18
  40:        0x10b73d8b1 - std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}::h8f274698cf915304
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/thread/mod.rs:474:17
  41:        0x10b7534a4 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h3f5ee8f562c0bcc0
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panic.rs:344:9
  42:        0x10b72ac45 - std::panicking::try::do_call::hc7ca871d6321fd0b
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panicking.rs:379:40
  43:        0x10b72cf8d - ___rust_try
  44:        0x10b72a6c1 - std::panicking::try::h67011bda65e0bc0b
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panicking.rs:343:19
  45:        0x10b753e94 - std::panic::catch_unwind::h03d7cd8b3a38bb63
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/panic.rs:431:14
  46:        0x10b73d07e - std::thread::Builder::spawn_unchecked::{{closure}}::h7e67fa4f6020f6d7
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/std/src/thread/mod.rs:473:30
  47:        0x10b741ed1 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h9a7c2579ff92d2b4
                               at /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_lang_rust/rust/work/rustc-1.51.0-src/library/core/src/ops/function.rs:227:5
  48:        0x10bd2023b - std::sys::unix::thread::Thread::new::thread_start::h2ede5f70c14488e7
  49:     0x7fff6a7db109 - __pthread_start

Commenting out line 370 in the mentioined lib.rs seems to fix the issue even though I don't know why. The program also seems to still work fine after commenting out this line, because the same thing is written in line 329.