Export: write a colr atom in ProRes MOVs (#2801)

ProRes renders had no colr atom, so the stream reported no primaries,
transfer or matrix. Write an nclc atom, as FilmCraft does for MOV, with
the codes of what the render path makes: the project's output space when
it has a working space, BT.709 otherwise.

sRGB output stays at transfer 1, which is still open on #340 and #464.
The frames don't change, so the pinned ProRes bytes move by exactly the
atom's 18 bytes.

crates/export/src/encode.rs

@@ -4,8 +4,8 @@
 
 use std::io::Write;
 
-use effectcraft_project::Comp;
 use effectcraft_project::render_queue::{AudioFormat, Channels, OutputFormat, ProResProfile};
+use effectcraft_project::{Comp, ProjectSettings};
 use effectcraft_time::{FrameRate, Tick};
 use filmcraft_isobmff::{Brand, ColorInfo, FourCc, Mp4Writer, PcmConfig, SampleEntry, TrackConfig, WriteSample, WriterOptions};
 use rayon::prelude::*;
@@ -164,6 +164,28 @@ struct ProRes {
     w: u32,
     h: u32,
     alpha: bool,
+    colr: ColorInfo,
+}
+
+/// The `colr` atom of a ProRes render: what its frames are, in H.273 code points. MOV uses
+/// QuickTime's `nclc`, which has no range flag; ProRes frames are limited range. The matrix is the
+/// one [`rgba_to_yuv_10`] always uses. Primaries and transfer follow the render path
+/// (`Pipe::output`): only a working space converts to the output space, so unmanaged frames pass
+/// through. sRGB output keeps transfer 1 rather than 13 (#340), and an alpha matte is not in the
+/// output space.
+fn prores_colr(settings: &ProjectSettings, channels: Channels) -> ColorInfo {
+    use effectcraft_project::ColorSpace as Space;
+    let output = settings.working_space.and(settings.output_space).filter(|_| channels != Channels::Alpha);
+    let (primaries, transfer) = match output {
+        None | Some(Space::Srgb | Space::Rec709) => (1, 1),
+        Some(Space::Rec2020) => (9, 1),
+        Some(Space::DisplayP3) => (12, 13),
+        Some(Space::Rec2100Pq) => (9, 16),
+        Some(Space::Rec2100Hlg) => (9, 18),
+        // H.273 has no code for the ACES primaries: unspecified, in linear light.
+        Some(Space::AcesCg | Space::Aces2065) => (2, 8),
+    };
+    ColorInfo::Nclc { primaries, transfer, matrix: 1 }
 }
 
 fn prores_profile(p: ProResProfile) -> filmcraft_prores::Profile {
@@ -179,14 +201,14 @@ fn prores_profile(p: ProResProfile) -> filmcraft_prores::Profile {
 }
 
 impl ProRes {
-    fn new(w: u32, h: u32, profile: ProResProfile, channels: Channels) -> ProRes {
+    fn new(w: u32, h: u32, profile: ProResProfile, channels: Channels, colr: ColorInfo) -> ProRes {
         // Alpha needs a 4444 flavour.
         let profile = if channels == Channels::Rgba && !profile.is_4444() { ProResProfile::P4444 } else { profile };
         let profile = prores_profile(profile);
         let alpha = channels == Channels::Rgba;
         let mut cfg = filmcraft_prores::EncoderConfig::new(profile, w, h);
         cfg.encode_alpha = alpha;
-        ProRes { enc: filmcraft_prores::Encoder::with_config(cfg), profile, w, h, alpha }
+        ProRes { enc: filmcraft_prores::Encoder::with_config(cfg), profile, w, h, alpha, colr }
     }
     fn is_444(&self) -> bool {
         matches!(self.profile, filmcraft_prores::Profile::P4444 | filmcraft_prores::Profile::P4444Xq)
@@ -195,7 +217,11 @@ impl ProRes {
 
 impl VideoEncoder for ProRes {
     fn sample_entry(&self) -> SampleEntry {
-        SampleEntry::prores(FourCc(self.profile.fourcc()), self.w as u16, self.h as u16)
+        let mut entry = SampleEntry::prores(FourCc(self.profile.fourcc()), self.w as u16, self.h as u16);
+        if let Some(v) = entry.video.as_mut() {
+            v.color = Some(self.colr.clone());
+        }
+        entry
     }
     fn encode(&mut self, rgba: &[u8], _index: u64) -> Result<Vec<Packet>> {
         let chroma = if self.is_444() { filmcraft_prores::ChromaFormat::Yuv444 } else { filmcraft_prores::ChromaFormat::Yuv422 };
@@ -301,7 +327,10 @@ pub(crate) async fn movie(job: &Cx<'_>, comp: &Comp, w: u32, h: u32, st: &mut St
         OutputFormat::Hevc => Box::new(crate::hevc_av1::Hevc::new(w, h, rate, job.output)?),
         OutputFormat::Av1 => Box::new(crate::hevc_av1::Av1::new(w, h, rate, job.output)?),
         OutputFormat::Uncompressed => Box::new(crate::uncompressed::Raw::new(w, h, channels == Channels::Rgba)?),
-        _ => Box::new(ProRes::new(w, h, job.output.prores_profile, if channels == Channels::Alpha { Channels::Rgb } else { channels })),
+        _ => {
+            let colr = prores_colr(&job.project.settings, channels);
+            Box::new(ProRes::new(w, h, job.output.prores_profile, if channels == Channels::Alpha { Channels::Rgb } else { channels }, colr))
+        }
     };
     let brand = if matches!(fmt, OutputFormat::ProRes | OutputFormat::Uncompressed) { Brand::Mov } else { Brand::Mp4 };
     let batch = batch_size();