videotoolbox

Safe, zero-runtime-dependency Rust bindings for Apple's VideoToolbox framework — hardware-accelerated H.264, HEVC, and ProRes codecs on macOS.

Status: experimental. Encoder is functional; decoder, pixel transfer, and multi-pass support are planned.

Features

• Hardware-accelerated encoding — H.264, HEVC, and ProRes 422/4444
• Direct IOSurface input — encode zero-copy from screencapturekit / camera output via apple-cf::iosurface
• Builder pattern — fluent configuration of bitrate, frame rate, keyframe interval, real-time mode
• Pure C bindings — no Swift bridge, no bindgen, no procedural macros
• Single dependency — only apple-cf for shared types

Why not bindgen?

The full VideoToolbox C surface is ~200 symbols, but the useful set for an encoder is closer to 15. Hand-writing those declarations gives us:

• No build-time dependency on clang
• Type-safe Rust enums for codec types (instead of raw u32 four-character codes)
• Builder APIs that map ergonomically to VT's CFDictionary property bag

Requirements

• macOS 13.0+
• Apple Silicon or Intel Mac with hardware video encoder

Quick start

use videotoolbox::prelude::*;
use apple_cf::iosurface::{IOSurface, IOSurfaceLockOptions};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Allocate a 1920×1080 BGRA IOSurface.
    let surface = IOSurface::create(1920, 1080, u32::from_be_bytes(*b"BGRA"), 4)
        .ok_or("failed to allocate")?;

    // Build a real-time H.264 encoder.
    let encoder = CompressionSession::builder(1920, 1080, Codec::H264)
        .with_real_time(true)
        .with_average_bit_rate(8_000_000)
        .with_expected_frame_rate(60.0)
        .with_max_keyframe_interval(120)
        .build()?;

    // Encode one frame and inspect the resulting CMSampleBuffer.
    let encoded = encoder.encode(&surface, (0, 60))?;
    println!("Got {} bytes of H.264", encoded.data.len());

    if let Some(sb) = encoded.cm_sample_buffer() {
        // Hand `sb` straight to avassetwriter::Writer::append_sample for
        // zero-copy muxing — no raw pointer hand-off needed.
        let _ = sb.is_valid();
    }

    Ok(())
}

Composes with the rest of the doom-fish stack

screencapturekit-rs ──► IOSurface ──► videotoolbox-rs ──► H.264 bytes
                                              ↓
                                        avassetwriter-rs (future)
                                              ↓
                                          .mp4 file

Roadmap

• VTCompressionSession (encoder)
• VTDecompressionSession (decoder)
• VTPixelTransferSession (pixel format / colour space conversion)
• VTMultiPassStorage (two-pass encoding for offline workflows)
• Async encode API via VTCompressionSessionEncodeFrameWithOutputHandler
• HEVC profile-level helpers
• HDR metadata support

License

Licensed under either of Apache-2.0 or MIT at your option.