fq/format/flac/flac_metadatablocks.go

package flac

// TODO: 24 bit picture length truncate warning

import (
	"github.com/wader/fq/format"
	"github.com/wader/fq/format/registry"
	"github.com/wader/fq/pkg/decode"
	"github.com/wader/fq/pkg/ranges"
)

var flacPicture []*decode.Format
var vorbisCommentFormat []*decode.Format

func init() {
	registry.MustRegister(&decode.Format{
		Name:        format.FLAC_METADATABLOCKS,
		Description: "FLAC metadatablocks",
		DecodeFn:    metadatablocskDecode,
		RootV:       decode.Array{},
		RootName:    "metadatablocks",
		Dependencies: []decode.Dependency{
			{Names: []string{format.FLAC_PICTURE}, Formats: &flacPicture},
			{Names: []string{format.VORBIS_COMMENT}, Formats: &vorbisCommentFormat},
		},
	})
}

const (
	MetadataBlockStreaminfo    = 0
	MetadataBlockPadding       = 1
	MetadataBlockApplication   = 2
	MetadataBlockSeektable     = 3
	MetadataBlockVorbisComment = 4
	MetadataBlockCuesheet      = 5
	MetadataBlockPicture       = 6
)

var metadataBlockNames = map[uint]string{
	MetadataBlockStreaminfo:    "Streaminfo",
	MetadataBlockPadding:       "Padding",
	MetadataBlockApplication:   "Application",
	MetadataBlockSeektable:     "Seektable",
	MetadataBlockVorbisComment: "Vorbis comment",
	MetadataBlockCuesheet:      "Cuesheet",
	MetadataBlockPicture:       "Picture",
}

func metadatablocskDecode(d *decode.D, in interface{}) interface{} {
	mb := format.FlacMetadatablocksOut{}

	isLastBlock := false
	for !isLastBlock {
		d.FieldStructFn("metadatablock", func(d *decode.D) {
			isLastBlock = d.FieldBool("last_block")
			typ := d.FieldUFn("type", func() (uint64, decode.DisplayFormat, string) {
				t := d.U7()
				name := "Unknown"
				if s, ok := metadataBlockNames[uint(t)]; ok {
					name = s
				}
				return t, decode.NumberDecimal, name
			})
			length := d.FieldU24("length")

			switch typ {
			case MetadataBlockStreaminfo:
				d.FieldU16("minimum_block_size")
				d.FieldU16("maximum_block_size")
				d.FieldU24("minimum_frame_size")
				d.FieldU24("maximum_frame_size")
				sampleRate := d.FieldU("sample_rate", 20)
				// <3> (number of channels)-1. FLAC supports from 1 to 8 channels
				d.FieldUFn("channels", func() (uint64, decode.DisplayFormat, string) { return d.U3() + 1, decode.NumberDecimal, "" })
				// <5> (bits per sample)-1. FLAC supports from 4 to 32 bits per sample. Currently the reference encoder and decoders only support up to 24 bits per sample.
				bitPerSample := d.FieldUFn("bits_per_sample", func() (uint64, decode.DisplayFormat, string) {
					return d.U5() + 1, decode.NumberDecimal, ""
				})
				totalSamplesInStream := d.FieldU("total_samples_in_stream", 36)
				md5Range := ranges.Range{Start: d.Pos(), Len: 16 * 8}
				d.FieldBitBufLen("md5", 16*8)

				mb.StreamInfo = format.FlacMetadatablockStreamInfo{
					SampleRate:           sampleRate,
					BitPerSample:         bitPerSample,
					TotalSamplesInStream: totalSamplesInStream,
					MD5Range:             md5Range,
				}
				mb.HasStreamInfo = true
			case MetadataBlockVorbisComment:
				d.FieldFormatLen("comment", int64(length*8), vorbisCommentFormat, nil)
			case MetadataBlockPicture:
				d.FieldFormatLen("picture", int64(length*8), flacPicture, nil)
			case MetadataBlockSeektable:
				seektableCount := length / 18
				d.FieldArrayFn("seekpoints", func(d *decode.D) {
					for i := uint64(0); i < seektableCount; i++ {
						d.FieldStructFn("seekpoint", func(d *decode.D) {
							d.FieldUFn("sample_number", func() (uint64, decode.DisplayFormat, string) {
								n := d.U64()
								d := ""
								if n == 0xffffffffffffffff {
									d = "Placeholder"
								}
								return n, decode.NumberDecimal, d
							})
							d.FieldU64("offset")
							d.FieldU16("number_of_samples")
						})
					}
				})
			default:
				d.FieldBitBufLen("data", int64(length*8))
			}
		})
	}

	return mb
}