Make mp4 parsing **a lot** faster & tremendously lower memory overhead

Cargo.lock

@@ -6181,6 +6181,7 @@ name = "re_video"
 version = "0.20.0-alpha.1+dev"
 dependencies = [
  "cfg_aliases 0.2.1",
+ "criterion",
  "crossbeam",
  "econtext",
  "indicatif",

crates/store/re_video/Cargo.toml

@@ -62,7 +62,7 @@ dav1d = { workspace = true, optional = true, default-features = false, features
 
 [dev-dependencies]
 indicatif.workspace = true
-
+criterion.workspace = true
 
 # For build.rs:
 [build-dependencies]
@@ -71,3 +71,8 @@ cfg_aliases.workspace = true
 
 [[example]]
 name = "frames"
+
+
+[[bench]]
+name = "video_load_bench"
+harness = false

crates/store/re_video/benches/video_load_bench.rs

@@ -0,0 +1,15 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn video_load(c: &mut Criterion) {
+    let video = include_bytes!("../../../../tests/assets/video/Big_Buck_Bunny_1080_10s_av1.mp4");
+    c.bench_function("video_load", |b| {
+        b.iter_batched(
+            || {},
+            |()| re_video::VideoData::load_from_bytes(video, "video/mp4"),
+            criterion::BatchSize::LargeInput,
+        );
+    });
+}
+
+criterion_group!(benches, video_load);
+criterion_main!(benches);