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简介
H.264流是由很多个NALU块组成，每个NALU通过起始码startcode分隔。
起始码有两个：0x000001和0x00000001，所以只要在代码中搜索起始码对其进行分割就可以得到一个完整的NALU块，之后在解析每个NAUL块中的字段。
通过字段UnitType可以得到当前NALU块的类型。
实现
测试文件下载地址：github.com/leixiaohua1…
package h264
import (
"sync"
log "github.com/sirupsen/logrus"
)
const (
DEFAULT_CAP int = 1024 * 1024 * 4
// NALU类型
NALU_TYPE_SLICE = 1
NALU_TYPE_DPA = 2
NALU_TYPE_DPB = 3
NALU_TYPE_DPC = 4
NALU_TYPE_IDR = 5
NALU_TYPE_SEI = 6
NALU_TYPE_SPS = 7
NALU_TYPE_PPS = 8
NALU_TYPE_AUD = 9
NALU_TYPE_EOSEQ = 10
NALU_TYPE_EOSTREAM = 11
NALU_TYPE_FILL = 12
// 优先级
NALU_PRIORITY_DISPOSABLE = 0
NALU_PRIRITY_LOW = 1
NALU_PRIORITY_HIGH = 2
NALU_PRIORITY_HIGHEST = 3
)
type NaluHead struct {
StartCodeLen int
Forbidden int
Reference int
UnitType int
}
type H264Buffer struct {
mutex sync.Mutex
data []byte
dataMaxSize int
rPtr int
naluHeads []*NaluHead // NALU块信息
iFrameIndex []int // I帧索引列表
}
func NewH264Buffer(cap int) *H264Buffer {
return &H264Buffer{
data: make([]byte, 0, cap),
dataMaxSize: cap,
rPtr: 0,
naluHeads: make([]*NaluHead, 0),
iFrameIndex: make([]int, 0),
}
}
func (buf *H264Buffer) Push(d []byte) {
buf.mutex.Lock()
defer buf.mutex.Unlock()
log.Info("H264Buffer push data")
if len(d) > buf.dataMaxSize {
return
}
// 计算超出的字节数
over := len(buf.data) + len(d) - buf.dataMaxSize
if over > 0 {
// 左移超出的字节数
buf.data = buf.data[over:]
buf.rPtr = buf.rPtr - over
}
buf.data = append(buf.data, d...)
// 更新nalu信息
buf.updateNALU()
log.Info("I frame indexs: ", buf.iFrameIndex)
}
func (buf *H264Buffer) getNALUHead(headIdx int) *NaluHead {
return &NaluHead{
Forbidden: int(buf.data[headIdx] >> 7),
Reference: int((buf.data[headIdx] << 1) >> 6),
UnitType: int((buf.data[headIdx] << 3) >> 3),
}
}
func (buf *H264Buffer) updateNALU() {
buf.naluHeads = make([]*NaluHead, 0)
buf.iFrameIndex = make([]int, 0)
for i := 0; i < len(buf.data)-5; i++ {
if buf.data[i] == 0 && buf.data[i+1] == 0 {
if buf.data[i+2] == 1 {
head := buf.getNALUHead(i + 3)
head.StartCodeLen = 3
// 起始码长度为3的情况
buf.naluHeads = append(buf.naluHeads, head)
if head.UnitType == NALU_TYPE_IDR {
buf.iFrameIndex = append(buf.iFrameIndex, i)
}
}
if buf.data[i+2] == 0 && buf.data[i+3] == 1 {
head := buf.getNALUHead(i + 4)
head.StartCodeLen = 4
// 起始码长度为4的情况
buf.naluHeads = append(buf.naluHeads, head)
if head.UnitType == NALU_TYPE_IDR {
buf.iFrameIndex = append(buf.iFrameIndex, i)
}
}
}
}
}
func (buf *H264Buffer) NaluInfo() {
buf.mutex.Lock()
defer buf.mutex.Unlock()
log.Info("|Index\t|\tForbidden\t|\tReference\t|\tUnitType|")
for i, v := range buf.naluHeads {
reference := "UNKNOW"
switch v.Reference {
case NALU_PRIORITY_DISPOSABLE:
reference = "DISPOSABLE"
case NALU_PRIRITY_LOW:
reference = "LOW"
case NALU_PRIORITY_HIGH:
reference = "HIGH"
case NALU_PRIORITY_HIGHEST:
reference = "HIGHEST"
}
naluType := "UNKNOW"
switch v.UnitType {
case NALU_TYPE_SLICE:
naluType = "SLICE"
case NALU_TYPE_DPA:
naluType = "DPA"
case NALU_TYPE_DPB:
naluType = "DPB"
case NALU_TYPE_DPC:
naluType = "DPC"
case NALU_TYPE_IDR:
naluType = "IDR"
case NALU_TYPE_SEI:
naluType = "SEI"
case NALU_TYPE_SPS:
naluType = "SPS"
case NALU_TYPE_PPS:
naluType = "PPS"
case NALU_TYPE_AUD:
naluType = "AUD"
case NALU_TYPE_EOSEQ:
naluType = "EOSEQ"
case NALU_TYPE_EOSTREAM:
naluType = "EOSTREAM"
case NALU_TYPE_FILL:
naluType = "FILL"
}
log.Info("|Index: ", i, "\t\t| StartCodeLen: ", v.StartCodeLen, "\t| Forbidden: ", v.Forbidden,
"\t| Reference: ", reference, "\t| UnitType: ", naluType)
}
}
func (buf *H264Buffer) Pop() []byte {
buf.mutex.Lock()
defer buf.mutex.Unlock()
d := buf.data[buf.rPtr:]
buf.rPtr = len(buf.data) - 1
return d
}
func (buf *H264Buffer) PopLastGOP() []byte {
buf.mutex.Lock()
defer buf.mutex.Unlock()
if len(buf.iFrameIndex) == 0 {
log.Info("no I Frame")
return make([]byte, 0)
}
idx := buf.iFrameIndex[len(buf.iFrameIndex)-1]
d := buf.data[idx:]
log.Info("GOP size: ", len(d))
return d
}
测试代码
func main() {
d, err := ioutil.ReadFile("sintel.h264")
if err != nil {
log.Fatal(err)
}
buffer := h264.NewH264Buffer(h264.DEFAULT_CAP)
buffer.Push(d)
buffer.NaluInfo()
}
