这里有三种方法:
1.利用iOS的AVAssetWritter
2.FFmpeg
3.MP4V2
本文使用第三种:
本地h264和aac封装成MP4:
1.读取h264和aac文件的数据
NSString *h264FilePath = [[NSBundle mainBundle] pathForResource:@"文件名" ofType:@".h264"];
NSData *h264Data = [NSData dataWithContentsOfFile:h264FilePath];
//获取音频数据的代码同理
2.切割数据
这里需要考虑你读取到的数据是音频和视频分开的还是合在一起的.
对于合在一起的情况,根据公司定义好的规则把音视频数据切割.对于分开的,按照音视频的规则切割即可,由于合在一起的不好公开,以下贴上音视频分开的情况
//视频
//按照NALU切割视频数据,NALU一般以 0x00 0x00 0x00 0x01 或者 0x00 0x00 0x01分隔开
uint8_t *videoData = (uint8_t*)[h264Data bytes];
int j = 0;
int lastJ = 0;
while (j < h264Data.length ) {
if (videoData[j] == 0x00 &&
videoData[j + 1] == 0x00 &&
videoData[j + 2] == 0x00 &&
videoData[j + 3] == 0x01) {
if (j > 0) {
int frame_size = j - lastJ;
NSData *buff = [NSData dataWithBytes:&videoData[lastJ] length:frame_size];
lastJ = j;
[mp4v2Tool addVideoData:buff];
}
}else if (j == h264Data.length - 1) {
int frame_size = j - lastJ;
NSData *buff = [NSData dataWithBytes:&videoData[lastJ] length:frame_size];
lastJ = j;
[mp4v2Tool addVideoData:buff];
}
j++;
}
//音频
uint8_t *voiceData = (uint8_t*)[aacData bytes];
j = 0;
lastJ = 0;
while (j < aacData.length) {
if (voiceData[j] == 0xff &&
(voiceData[j + 1] & 0xf0) == 0xf0) {
if (j > 0) {
//0xfff判断AAC头
int frame_size = j - lastJ;
if (frame_size > 7) {
NSData *buff = [NSData dataWithBytes:&voiceData[lastJ] length:frame_size];
// NSLog(@"%@",buff);
lastJ = j;
[mp4v2Tool addAudioData:buff];
}
}
}else if (j == aacData.length - 1) {
int frame_size = j - lastJ;
if (frame_size > 7) {
NSData *buff = [NSData dataWithBytes:&voiceData[lastJ] length:frame_size];
// NSLog(@"%@",buff);
lastJ = j;
[mp4v2Tool addAudioData:buff];
}
}
j++;
}
3.创建MP4文件及设置相关参数
/*
功能：创建MP4文件句柄。
返回：MP4文件句柄。
参数：fileName 要录制的MP4文件名；flags 创建文件类型，如果要创建普通文件用默认值0就可以，如要录制大于4G的MP4文件此处要设置MP4_CREATE_64BIT_DATA。
*/
m_mp4FHandle = MP4Create(strFilePath);
//m_vTimeScale一般为9000;
MP4SetTimeScale(m_mp4FHandle, m_vTimeScale);
//对于g711
//alaw format
/*
初始化添加音频为PCM
默认采样率是20ms
*/
m_aTrackId = MP4AddALawAudioTrack(m_mp4FHandle, audioSampleRate);
MP4SetTrackIntegerProperty(m_mp4FHandle, m_aTrackId, "mdia.minf.stbl.stsd.alaw.channels", 1);
MP4SetTrackIntegerProperty(m_mp4FHandle, m_aTrackId, "mdia.minf.stbl.stsd.alaw.sampleSize", 8);
4.写入视频数据
根据切割到的nalu获取相关数据
typedef struct _MP4ENC_NaluUnit
{
int frameType; //帧类型
int frameLen; //nalu长度，不包括00 00 00 01
unsigned char *pframeBuf; //不包括00 00 00 01
}MP4ENC_NaluUnit;
static int ReadOneNaluFromBuf(const unsigned char *buffer,
unsigned int nBufferSize,
unsigned int offSet,
MP4ENC_NaluUnit &nalu)
{
unsigned int i = offSet;
while(i < nBufferSize)
{
if(buffer[i++] == 0x00 && buffer[i] == 0x00 && buffer[i+1] == 0x00 && buffer[i+2] == 0x01)
{
unsigned int pos = i+3;
unsigned int iEnd = i+3;
unsigned int posEnd = 0;
while (pos < nBufferSize)
{
if(buffer[pos++] == 0x00 && buffer[pos] == 0x00 && buffer[pos+1] == 0x00 && buffer[pos+2] == 0x01)
{
posEnd = pos+3;
break;
}
posEnd = pos;
}
if(posEnd == nBufferSize)
{
nalu.frameLen = posEnd-iEnd;
}
else
{
nalu.frameLen = (posEnd - 4) - iEnd;
}
nalu.frameType = buffer[iEnd]&0x1f;
nalu.pframeBuf = (unsigned char*)&buffer[iEnd];
return (nalu.frameLen+iEnd-offSet);
}
}
return 0;
}
//获取sps
if(m_bGetSpsSlice == false)
{
m_vTrackId = MP4AddH264VideoTrack(m_mp4FHandle,
m_vTimeScale,
m_vTimeScale/m_vFrateR,
m_vWidth,
m_vHeight,
nalu.pframeBuf[1],
nalu.pframeBuf[2],
nalu.pframeBuf[3],
3);
if(m_vTrackId == MP4_INVALID_TRACK_ID)
{
printf("add viedo trake failed.\n");
return -1;
}
MP4SetVideoProfileLevel(m_mp4FHandle, 1);
MP4AddH264SequenceParameterSet(m_mp4FHandle, m_vTrackId, nalu.pframeBuf, nalu.frameLen);
m_bGetSpsSlice = true;
}
}
//获取pps
if (nalu.frameType == 0x08) //pps
{
if(m_bGetPpsSlice == false)
{
MP4AddH264PictureParameterSet(m_mp4FHandle, m_vTrackId, nalu.pframeBuf, nalu.frameLen);
m_bGetPpsSlice = true;
}
}
//写入数据
if((nalu.frameType != 0x06) && (nalu.frameType != 0x0d))
{
if((m_vTrackId != MP4_INVALID_TRACK_ID) && m_bGetSpsSlice && m_bGetPpsSlice && m_bRecord)
{
//当trackID有效,获取到sps,pps时开始写入数据
int datalen = nalu.frameLen + 4;
BYTE *data = new BYTE[datalen];
data[0] = nalu.frameLen >> 24;
data[1] = nalu.frameLen >> 16;
data[2] = nalu.frameLen >> 8;
data[3] = nalu.frameLen & 0xff;
memcpy(data+4, nalu.pframeBuf, nalu.frameLen);
if(!MP4WriteSample(m_mp4FHandle, m_vTrackId, (const uint8_t*)data, datalen,m_vTimeScale/m_vFrateR))
{
printf("write a viedo failed\n");
delete []data;
return -1;
}
m_bGetIFrame = true;
delete []data;
}
}
5.写入音频数据
int CMp4Encoder::WriteAudioTrack(BYTE* _aacData,int _aacSize)
{
if(m_aTrackId == MP4_INVALID_TRACK_ID)
{
return -1;
}
if (!m_bGetIFrame)
{
return -1;
}
if(!m_bRecord)
{
return -1;
}
if(m_audioFormat == WAVE_FORMAT_AAC)
{
bool result = MP4WriteSample(m_mp4FHandle, m_aTrackId,(const uint8_t*) _aacData+7, _aacSize-7 ,1024, 0, 1);
if (result == true) {
printf("add success!\n");
}else {
printf("add failed!\n");
}
}
else if (m_audioFormat == WAVE_FORMAT_G711)
{
MP4WriteSample(m_mp4FHandle, m_aTrackId,(const uint8_t*) _aacData, _aacSize ,MP4_INVALID_DURATION, 0, 1);
}
return _aacSize;
}
6.关闭
MP4Close(m_mp4FHandle);
MP4V2 编译iOS下使用的.a
MP4V2-iOS
下载后运行脚本即可
相关知识:
常用NAL(Network Abstract Layer)头的取值:
0x67:SPS
0x68:PPS
0x65:IDR
0x61:non-IDR Slice
0x01:B Slice
0x06:SEI
0x09:AU Delimiter
注意点:
需要先获取到sps和pps,序列参数集 SPS 作用于一系列连续的编码图像，而图像参数集 PPS 作用于编码视频序列中一个或多个独立 的图像。如果解码器没能正确接收到这两个参数集，那么其他NALU 也是无法解码的。因此它们一般在发送其它 NALU 之前发送，并且使用不同的信道或者更加可靠的传输协议(如TCP)进行传输，也可以重复传输。
视频帧率和音频采样率要设置正确,否则播放速度不正常或者音视频不同步.
