feat(video): add native AVC/HEVC and synchronized AAC MP4 streaming

packages/video/src/codecs/video/rgb_i420.zigadded+37-0

Changes to packages/video/src/codecs/video/rgb_i420.zig

		@@ -0,0 +1,37 @@
	1	+//! Home RGB -> limited-range BT.601 I420. Adapted from perf/simd.zig, with
	2	+//! checked strides and actual 2x2 chroma averaging rather than corner sampling.
	3	+const std = ;
	4	+pub fn convert(rgb: []const u8, width: u32, height: u32, stride: u32, out: []u8) !void {
	5	+ if (width == 0 or height == 0 or (width | height) & 1 != 0 or stride < @as(u64, width) * 3) return error.InvalidGeometry;
	6	+ const pixels = std.math.mul(usize, width, height) catch return error.InvalidGeometry;
	7	+ if (rgb.len < @as(u64, stride) * (height - 1) + @as(u64, width) * 3 or out.len < pixels + pixels / 2) return error.InvalidGeometry;
	8	+ for (0..height / 2) |cy| {
	9	+ for (0..width / 2) |cx| {
	10	+ var r: i32 = 0;
	11	+ var g: i32 = 0;
	12	+ var b: i32 = 0;
	13	+ for (0..2) |dy| {
	14	+ for (0..2) |dx| {
	15	+ const x = cx * 2 + dx;
	16	+ const y = cy * 2 + dy;
	17	+ const p = rgb[y * stride + x * 3 ..][0..3];
	18	+ out[y * width + x] = @intCast(((66 * @as(i32, p[0]) + 129 * @as(i32, p[1]) + 25 * @as(i32, p[2]) + 128) >> 8) + 16);
	19	+ r += p[0];
	20	+ g += p[1];
	21	+ b += p[2];
	22	+ }
	23	+ }
	24	+ const uv = cy * (width / 2) + cx;
	25	+ out[pixels + uv] = @intCast(((-38 * r - 74 * g + 112 * b + 512) >> 10) + 128);
	26	+ out[pixels + pixels / 4 + uv] = @intCast(((112 * r - 94 * g - 18 * b + 512) >> 10) + 128);
	27	+ }
	28	+ }
	29	+}
	30	+test "strided RGB conversion averages chroma and rejects truncation" {
	31	+ var out: [6]u8 = undefined;
	32	+ const rgb = [_]u8{ 255, 0, 0, 0, 255, 0, 99, 99, 0, 0, 255, 255, 255, 255 };
	33	+ try convert(&rgb, 2, 2, 8, &out);
	34	+ try std.testing.expectEqualSlices(u8, &.{ 82, 144, 41, 235, 128, 128 }, &out);
	35	+ try std.testing.expectError(error.InvalidGeometry, convert(rgb[0..13], 2, 2, 8, &out));
	36	+ try std.testing.expectError(error.InvalidGeometry, convert(&rgb, 1, 2, 8, &out));
	37	+}