This crate is a slightly-more-polished and MIT-licensed version of
resource.rs. So far it has one advantage: running the tests doesn't
require RUST_TEST_THREADS=1.
I should have submitted/pushed more incrementally but just played with it on
my computer as I was learning the language. The new Rust version more or less
matches the functionality of the current C++ version, although there are many
caveats listed below.
Upgrade notes: when moving from the C++ version, I recommend dropping and
recreating the "recording_cover" index in SQLite3 to pick up the addition of
the "video_sync_samples" column:
$ sudo systemctl stop moonfire-nvr
$ sudo -u moonfire-nvr sqlite3 /var/lib/moonfire-nvr/db/db
sqlite> drop index recording_cover;
sqlite3> create index ...rest of command as in schema.sql...;
sqlite3> ^D
Some known visible differences from the C++ version:
* .mp4 generation queries SQLite3 differently. Before it would just get all
video indexes in a single query. Now it leads with a query that should be
satisfiable by the covering index (assuming the index has been recreated as
noted above), then queries individual recording's indexes as needed to fill
a LRU cache. I believe this is roughly similar speed for the initial hit
(which generates the moov part of the file) and significantly faster when
seeking. I would have done it a while ago with the C++ version but didn't
want to track down a lru cache library. It was easier to find with Rust.
* On startup, the Rust version cleans up old reserved files. This is as in the
design; the C++ version was just missing this code.
* The .html recording list output is a little different. It's in ascending
order, with the most current segment shorten than an hour rather than the
oldest. This is less ergonomic, but it was easy. I could fix it or just wait
to obsolete it with some fancier JavaScript UI.
* commandline argument parsing and logging have changed formats due to
different underlying libraries.
* The JSON output isn't quite right (matching the spec / C++ implementation)
yet.
Additional caveats:
* I haven't done any proof-reading of prep.sh + install instructions.
* There's a lot of code quality work to do: adding (back) comments and test
coverage, developing a good Rust style.
* The ffmpeg foreign function interface is particularly sketchy. I'd
eventually like to switch to something based on autogenerated bindings.
I'd also like to use pure Rust code where practical, but once I do on-NVR
motion detection I'll need to existing C/C++ libraries for speed (H.264
decoding + OpenCL-based analysis).
I'm seeing what is possible performance-wise in the current C++ before
trying out Go and Rust implementations.
* use the google benchmark framework and some real data.
* use release builds - I hadn't done this in a while, and there were a
few compile errors that manifested only in release mode. Update the
readme to suggest using a release build.
* optimize the varint decoder and SampleIndexIterator to branch less.
* enable link-time optimization for release builds.
* add some support for feedback-directed optimization. Ideally "make"
would automatically produce the "generate" build outputs with a
different object/library/executable suffix, run the generate
benchmark, and then produce the "use" builds. This is not that fancy;
you have to run an arcane command:
alias cmake='cmake -DCMAKE_BUILD_TYPE=Release'
cmake -DPROFILE_GENERATE=true -DPROFILE_USE=false .. && \
make recording-bench && \
src/recording-bench && \
cmake -DPROFILE_GENERATE=false -DPROFILE_USE=true .. && \
make recording-bench && \
perf stat -e cycles,instructions,branches,branch-misses \
src/recording-bench --benchmark_repetitions=5
That said, the results are dramatic - at least 50% improvement. (The
results weren't stable before as small tweaks to the code caused a
huge shift in performance, presumably something something branch
alignment something something.)
* Changed README.md commensurately
* Add cameras.sql to .gitignore to not commit personal camera data
* Change CMakeLists.txt to explicitly refer to hand-built libevent dirs
