Support FLV demuxer.

Author: winlinvip

README.md

@@ -18,7 +18,7 @@ The core library including:
 - [x] [https](https/example_test.go): For https server over [lego/acme](https://github.com/xenolf/lego/tree/master/acme) of [letsencrypt](https://letsencrypt.org/).
 - [x] [gmoryx](gmoryx/README.md): A [gomobile](https://github.com/golang/mobile) API for go-oryx-lib.
 - [ ] [rtmp](rtmp/example_test.go): The RTMP protocol stack, for oryx.
-- [ ] [flv](flv/example_test.go): The FLV muxer, for oryx.
+- [ ] [flv](flv/example_test.go): The FLV muxer and demuxer, for oryx.
 
 Other audio/video libraries:
 

doc/video_file_format_spec_v10.pdf

@@ -20,3 +20,44 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 package flv_test
+
+import (
+	"github.com/ossrs/go-oryx-lib/flv"
+	"io"
+)
+
+func ExampleDemuxer() {
+	// To open a flv file, or http flv stream.
+	var r io.Reader
+
+	f := flv.NewDemuxer(r)
+
+	var err error
+	var version uint8
+	var hasVideo, hasAudio bool
+	if version, hasVideo, hasAudio, err = f.ReadHeader(); err != nil {
+		return
+	}
+
+	// Optional, user can check the header.
+	_ = version
+	_ = hasAudio
+	_ = hasVideo
+
+	var tagType flv.TagType
+	var tagSize, timestamp uint32
+	if tagType, tagSize, timestamp, err = f.ReadTagHeader(); err != nil {
+		return
+	}
+
+	var tag []byte
+	if tag, err = f.ReadTag(tagSize); err != nil {
+		return
+	}
+
+	// Using the FLV tag type, dts and body.
+	// Refer to @doc video_file_format_spec_v10.pdf, @page 9, @section FLV tags
+	_ = tagType
+	_ = timestamp
+	_ = tag
+}

flv/example_test.go

@@ -21,3 +21,110 @@
 
 // The oryx FLV package support bytes from/to FLV tags.
 package flv
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+// FLV Tag Type is the type of tag,
+// refer to @doc video_file_format_spec_v10.pdf, @page 9, @section FLV tags
+type TagType uint8
+
+const (
+	TagTypeForbidden  TagType = 0
+	TagTypeAudio      TagType = 8
+	TagTypeVideo      TagType = 9
+	TagTypeScriptData TagType = 18
+)
+
+func (v TagType) String() string {
+	switch v {
+	case TagTypeVideo:
+		return "Video"
+	case TagTypeAudio:
+		return "Audio"
+	case TagTypeScriptData:
+		return "Data"
+	default:
+		return "Forbidden"
+	}
+}
+
+// FLV Demuxer is used to demux FLV file.
+// Refer to @doc video_file_format_spec_v10.pdf, @page 7, @section The FLV File Format
+// A FLV file must consist the bellow parts:
+//	1. A FLV header, refer to @doc video_file_format_spec_v10.pdf, @page 8, @section The FLV header
+//	2. One or more tags, refer to @doc video_file_format_spec_v10.pdf, @page 9, @section FLV tags
+// @remark We always ignore the previous tag size.
+type Demuxer interface {
+	// Read the FLV header, return the version of FLV, whether hasVideo or hasAudio in header.
+	ReadHeader() (version uint8, hasVideo, hasAudio bool, err error)
+	// Read the FLV tag header, return the tag information, especially the tag size,
+	// then user can read the tag payload.
+	ReadTagHeader() (tagType TagType, tagSize, timestamp uint32, err error)
+	// Read the FLV tag body, drop the next 4 bytes previous tag size.
+	ReadTag(tagSize uint32) (tag []byte, err error)
+}
+
+// When FLV signature is not "FLV"
+var ErrSignature = errors.New("FLV signatures are illegal")
+
+// Create a demuxer object.
+func NewDemuxer(r io.Reader) Demuxer {
+	return &demuxer{
+		r: r,
+	}
+}
+
+type demuxer struct {
+	r io.Reader
+}
+
+func (v *demuxer) ReadHeader() (version uint8, hasVideo, hasAudio bool, err error) {
+	h := &bytes.Buffer{}
+	if _, err = io.CopyN(h, v.r, 13); err != nil {
+		return
+	}
+
+	p := h.Bytes()
+
+	if !bytes.Equal([]byte{byte('F'), byte('L'), byte('V')}, p[:3]) {
+		err = ErrSignature
+		return
+	}
+
+	version = uint8(p[3])
+	hasVideo = (p[4] & 0x01) == 0x01
+	hasAudio = ((p[4] >> 2) & 0x01) == 0x01
+
+	return
+}
+
+func (v *demuxer) ReadTagHeader() (tagType TagType, tagSize uint32, timestamp uint32, err error) {
+	h := &bytes.Buffer{}
+	if _, err = io.CopyN(h, v.r, 11); err != nil {
+		return
+	}
+
+	p := h.Bytes()
+
+	tagType = TagType(p[0])
+	tagSize = uint32(p[1])<<16 | uint32(p[2])<<8 | uint32(p[3])
+	timestamp = uint32(p[7])<<24 | uint32(p[4])<<16 | uint32(p[5])<<8 | uint32(p[6])
+
+	return
+}
+
+func (v *demuxer) ReadTag(tagSize uint32) (tag []byte, err error) {
+	h := &bytes.Buffer{}
+	if _, err = io.CopyN(h, v.r, int64(tagSize+4)); err != nil {
+		return
+	}
+
+	p := h.Bytes()
+	tag = p[0 : len(p)-4]
+
+	return
+}