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108 lines
2.7 KiB
Go
108 lines
2.7 KiB
Go
package flv
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import (
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"encoding/binary"
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"fmt"
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"github.com/lkmio/flv"
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)
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const (
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// HttpFlvBlockHeaderSize 在每块http-flv流的头部，预留指定大小的数据, 用于描述flv数据块的长度信息
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// http-flv是以文件流形式传输的http流, 格式如下: length\r\n|flv data\r\n
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// 我们对http-flv-block的封装: |block size[4]|skip count[2]|length\r\n|flv data\r\n
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HttpFlvBlockHeaderSize = 20
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)
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// GetHttpFLVBlock 跳过头部的无效数据，返回http-flv块
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func GetHttpFLVBlock(data []byte) []byte {
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return data[computeSkipBytesSize(data):]
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}
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// GetFLVTag 从http flv块中提取返回flv tag
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func GetFLVTag(block []byte) []byte {
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length := len(block)
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var offset int
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for i := 2; i < length; i++ {
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if block[i-2] == 0x0D && block[i-1] == 0x0A {
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offset = i
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break
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}
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}
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return block[offset : length-2]
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}
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type TagPacket struct {
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flv.Tag
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Raw []byte
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Offset int
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}
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// SplitHttpFlvBlock http-flv块分割为多个flv tag
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func SplitHttpFlvBlock(httpFlv []byte) []TagPacket {
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data := GetFLVTag(httpFlv)
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length := len(data)
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start := len(httpFlv) - length - 2
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var packets []TagPacket
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for i := 0; i < length; {
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tag := flv.UnmarshalTag(data[i:])
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offset := i
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i += flv.TagHeaderSize + tag.DataSize
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// 目前只需要保留第一个和最后一个tag
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if offset == 0 || i >= length {
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packets = append(packets, TagPacket{
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Tag: tag,
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Raw: data[offset:i],
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Offset: start + offset,
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})
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}
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}
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return packets
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}
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// 计算头部的无效数据, 返回http-flv的其实位置
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func computeSkipBytesSize(data []byte) int {
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return int(6 + binary.BigEndian.Uint16(data[4:]))
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}
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// FormatSegment 为切片添加包长和换行符
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func FormatSegment(segment []byte) []byte {
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writeSeparator(segment)
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return GetHttpFLVBlock(segment)
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}
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// 为http-flv数据块添加长度和换行符
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// @dst http-flv数据块, 头部需要空出HttpFlvBlockLengthSize字节长度, 末尾空出2字节换行符
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func writeSeparator(dst []byte) {
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// http-flv: length\r\n|flv data\r\n
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// http-flv-block: |block size[4]|skip count[2]|length\r\n|flv data\r\n
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// 写block size
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binary.BigEndian.PutUint32(dst, uint32(len(dst)-4))
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// 写flv实际长度字符串, 16进制表达
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flvSize := len(dst) - HttpFlvBlockHeaderSize - 2
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hexStr := fmt.Sprintf("%X", flvSize)
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// +2是跳过length后的换行符
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n := len(hexStr) + 2
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copy(dst[HttpFlvBlockHeaderSize-n:], hexStr)
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// 写跳过字节数量
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// -6是block size和skip count字段合计长度
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skipCount := HttpFlvBlockHeaderSize - n - 6
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binary.BigEndian.PutUint16(dst[4:], uint16(skipCount))
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// flv length字段和flv数据之间的换行符
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dst[HttpFlvBlockHeaderSize-2] = 0x0D
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dst[HttpFlvBlockHeaderSize-1] = 0x0A
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// 末尾换行符
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dst[len(dst)-2] = 0x0D
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dst[len(dst)-1] = 0x0A
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}
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