fq/format/mpeg/mpeg_pes.go

package mpeg

// TODO: probeable?

// http://dvdnav.mplayerhq.hu/dvdinfo/mpeghdrs.html

import (
	"log"

	"github.com/wader/fq/format"
	"github.com/wader/fq/format/registry"
	"github.com/wader/fq/pkg/bitio"
	"github.com/wader/fq/pkg/decode"
)

var pesPacketFormat []*decode.Format
var spuFormat []*decode.Format

func init() {
	registry.MustRegister(&decode.Format{
		Name:        format.MPEG_PES,
		Description: "MPEG Packetized elementary stream",
		DecodeFn:    pesDecode,
		Dependencies: []decode.Dependency{
			{Names: []string{format.MPEG_PES_PACKET}, Formats: &pesPacketFormat},
			{Names: []string{format.MPEG_SPU}, Formats: &spuFormat},
		},
	})
}

type subStream struct {
	b []byte
	l int
}

func pesDecode(d *decode.D, in interface{}) interface{} {
	substreams := map[int]*subStream{}

	prefix := d.PeekBits(24)
	if prefix != 0b0000_0000_0000_0000_0000_0001 {
		d.Invalid("no pes prefix found")
	}

	i := 0

	spuD := d.FieldArray("spus")

	d.FieldArrayFn("packets", func(d *decode.D) {
		for d.NotEnd() {
			dv, v, err := d.FieldTryFormat("packet", pesPacketFormat)
			if dv == nil || err != nil {
				log.Printf("errs[0]: %#+v\n", err)
				break
			}

			switch dvv := v.(type) {
			case subStreamPacket:
				s, ok := substreams[dvv.number]
				if !ok {
					s = &subStream{}
					substreams[dvv.number] = s
				}
				b, _ := dvv.bb.BytesRange(0, int(dvv.bb.Len()/8))
				s.b = append(s.b, b...)

				if s.l == 0 && len(b) >= 2 {
					s.l = int(b[0])<<8 | int(b[1])
					// TODO: zero l?
				}

				// TODO: is this how spu end is signalled?
				if s.l == len(s.b) {
					spuD.FieldFormatBitBuf("spu", bitio.NewBufferFromBytes(s.b, -1), spuFormat)
					s.b = nil
					s.l = 0
				}
			}

			i++
		}
	})

	return nil
}