go-mxl-pattern-generator/internal/flowdef/flowdef.go

// Package flowdef models and validates MXL flow-definition JSON.
package flowdef

import (
	"encoding/json"
	"fmt"

	"github.com/google/uuid"
)

const (
	FormatVideo   = "urn:x-nmos:format:video"
	FormatAudio   = "urn:x-nmos:format:audio"
	MediaTypeV210 = "video/v210"

	InterlaceProgressive = "progressive"
	ColorSpaceBT709      = "BT709"
)

type Common struct {
	Description string              `json:"description"`
	ID          string              `json:"id"`
	Tags        map[string][]string `json:"tags"`
	Format      string              `json:"format"`
	Label       string              `json:"label"`
	Parents     []string            `json:"parents"`
	MediaType   string              `json:"media_type"`
}

type Rational struct {
	Numerator   uint `json:"numerator"`
	Denominator uint `json:"denominator"`
}

type Video struct {
	Common

	GrainRate     Rational         `json:"grain_rate"`
	FrameWidth    uint             `json:"frame_width"`
	FrameHeight   uint             `json:"frame_height"`
	InterlaceMode string           `json:"interlace_mode"`
	ColorSpace    string           `json:"colorspace"`
	Components    []VideoComponent `json:"components"`
}

type Audio struct {
	Common

	SampleRate   Rational `json:"sample_rate"`
	ChannelCount uint     `json:"channel_count"`
	BitDepth     uint     `json:"bit_depth"`
}

type VideoComponent struct {
	Name     string `json:"name"`
	Width    uint   `json:"width"`
	Height   uint   `json:"height"`
	BitDepth uint   `json:"bit_depth"`
}

func NewV210Video(id string, width, height uint, rate Rational) (Video, error) {
	definition := Video{
		Common: Common{
			Description: "go-mxl-pattern-gen generated video",
			ID:          id,
			Tags: map[string][]string{
				"urn:x-nmos:tag:grouphint/v1.0": {"go-mxl-pattern-gen:Video"},
			},
			Format:    FormatVideo,
			Label:     "go-mxl-pattern-gen generated video",
			Parents:   []string{},
			MediaType: MediaTypeV210,
		},
		GrainRate:     rate,
		FrameWidth:    width,
		FrameHeight:   height,
		InterlaceMode: InterlaceProgressive,
		ColorSpace:    ColorSpaceBT709,
		Components: []VideoComponent{
			{Name: "Y", Width: width, Height: height, BitDepth: 10},
			{Name: "Cb", Width: width / 2, Height: height, BitDepth: 10},
			{Name: "Cr", Width: width / 2, Height: height, BitDepth: 10},
		},
	}
	if err := definition.Validate(); err != nil {
		return Video{}, err
	}
	return definition, nil
}

func ParseV210Video(data []byte) (Video, error) {
	var definition Video
	if err := json.Unmarshal(data, &definition); err != nil {
		return Video{}, fmt.Errorf("decode video flow definition: %w", err)
	}
	if err := definition.Validate(); err != nil {
		return Video{}, fmt.Errorf("invalid video flow definition: %w", err)
	}
	return definition, nil
}

func (v Video) Validate() error {
	if err := uuid.Validate(v.ID); err != nil {
		return fmt.Errorf("invalid id %q: %w", v.ID, err)
	}
	if v.Format != FormatVideo {
		return fmt.Errorf("format must be %q, got %q", FormatVideo, v.Format)
	}
	if v.MediaType != MediaTypeV210 {
		return fmt.Errorf("media_type must be %q, got %q", MediaTypeV210, v.MediaType)
	}
	if v.InterlaceMode != InterlaceProgressive {
		return fmt.Errorf("interlace_mode must be %q, got %q", InterlaceProgressive, v.InterlaceMode)
	}
	if v.ColorSpace != ColorSpaceBT709 {
		return fmt.Errorf("colorspace must be %q, got %q", ColorSpaceBT709, v.ColorSpace)
	}
	if v.FrameWidth == 0 || v.FrameWidth%6 != 0 {
		return fmt.Errorf("frame_width must be greater than zero and divisible by 6, got %d", v.FrameWidth)
	}
	if v.FrameHeight == 0 {
		return fmt.Errorf("frame_height must be greater than zero")
	}
	if v.GrainRate.Numerator == 0 || v.GrainRate.Denominator == 0 {
		return fmt.Errorf("grain_rate numerator and denominator must be greater than zero, got %d/%d",
			v.GrainRate.Numerator, v.GrainRate.Denominator)
	}

	want := []VideoComponent{
		{Name: "Y", Width: v.FrameWidth, Height: v.FrameHeight, BitDepth: 10},
		{Name: "Cb", Width: v.FrameWidth / 2, Height: v.FrameHeight, BitDepth: 10},
		{Name: "Cr", Width: v.FrameWidth / 2, Height: v.FrameHeight, BitDepth: 10},
	}
	if len(v.Components) != len(want) {
		return fmt.Errorf("v210 requires %d components, got %d", len(want), len(v.Components))
	}
	for i := range want {
		if v.Components[i] != want[i] {
			return fmt.Errorf("component %d must be %+v, got %+v", i, want[i], v.Components[i])
		}
	}
	return nil
}