EasyRTMPClient擴展支持HEVC(H.265)解決方案之兼容H264和H265幀數據解析詳解

在之前兩篇關於EasyRTMPClient擴展支持HEVC(H.265)解決方案的文章中，我們已經完成了對H265的支持，本文主要闡述將H26和H265支持兼容起來，實現不同視頻編碼格式的自適應兼容適配。

1. 根據CodecId判斷數據編碼類型

根據視頻編碼ID判斷視頻編碼類型，如果視頻編碼ID==FlvCodeId_Hevc（12）,則判斷視頻編碼格式爲H265，反之則爲H264（因爲目前我們只支持這兩種編碼格式的視頻推送），如下代碼所示：

    parser_VideoTag *video_tag = (parser_VideoTag*)(buf+parser_offset);
	FlvCodeId video_code_id = (FlvCodeId)(video_tag->code_id&0x0f);
	if (video_code_id == FlvCodeId_Hevc)
	{
		av_frame.u32AVFrameFlag = EASY_SDK_VIDEO_CODEC_H265;// HEVC;
	} 
	else
	{
		av_frame.u32AVFrameFlag = EASY_SDK_VIDEO_CODEC_H264;// 默認h264, 其他類型是否需要判斷?!;
	}

2. 數據幀頭部判斷

根據FLV/RTMP擴展支持H265標準，支持HEVC的VideoTagHeader定義如下圖所示：

即 當CodecID == 12時，AVCPacketType爲HEVCPacketType：

• 如果HEVCPacketType爲0，表示HEVCVIDEOPACKET中存放的是HEVC sequence header；

• 如果HEVCPacketType爲1，表示HEVCVIDEOPACKET中存放的是HEVC NALU；

• 如果HEVCPacketType爲2，表示HEVCVIDEPACKET中存放的是HEVC end of sequence，即HEVCDecoderConfigurationRecord；

而當CodecID == 7時，AVCPacketType爲AVCPacketType：

• 如果AVCPacketType爲0，表示HEVCVIDEOPACKET中存放的是AVC sequence header；

• 如果AVCPacketType爲1，表示HEVCVIDEOPACKET中存放的是AVC NALU；

• 如果AVCPacketType爲2，表示HEVCVIDEPACKET中存放的是AVC end of sequence，即AVCDecoderConfigurationRecord；

EasyRTMPClient對sequence header的解析函數如下代碼段所示：

int ParserVideoSequencePacket(FlvCodeId video_code_id, char *buf,int len)
{
	int parser_offset = 0;
	char *parser_config = buf;
	if (video_code_id == FlvCodeId_Hevc)
	{
		if(len <= sizeof(Parser_HEVCDecoderConfigurationRecord))
		{
			return -1001;
		}			
 		......’
		//Parser HEVCDecoderConfigurationRecord 
		......
		rtmpclient_h265_decode_sps((unsigned char *)sps_buf_, sps_len_, width_, height_);	
	} 
	else
	{
		if(len <= sizeof(parser_AVCDecoderHeader))
		{
			return -1001;
		}
 		......’
		//Parser HEVCDecoderHeader
		......
		rtmpclient_h264_decode_sps((unsigned char *)sps_buf_, sps_len_, width_, height_);
	}

    return 0;
}

3. 視頻數據體幀數據nalu類型判斷

根據FLV/RTMP擴展支持協議標準，支持H265的VideoTagBody定義如下, 擴展後的VideoTagBody如下圖所示(紅色字體爲HEVC新增內容)：：

當CodecID爲12時，VideoTagBody中存放的就是HEVC視頻幀內容。
EasyRTMPClient視頻幀nalu解析如下代碼所示：

int ParserOneVideoNalu(EasyRTMPClient_AV_Frame& av_frame,char *buf,int len,char* processbuf)
{
    if(processbuf == NULL || buf == NULL || len == 0)
    {
        return -3001;
    }
    if(sps_len_ == 0 || pps_len_ == 0)
    {
        printf("do not get sequence head yet\n");
        return -3002;
    }

    int parse_offset = 0;
    int nalu_len = 0;
    int nalu_type = 0;
    int processlen = 0;
    while(parse_offset < len - 4)
    {
        nalu_len = ntohl(*(int*)(buf + parse_offset));  
        parse_offset += 4;
        //如果視頻幀編碼類型爲H265
		if(av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265)
		{
			nalu_type = (buf[parse_offset] >> 1) & 0x3F;
			if(nalu_type == e_H265_NAL_UNIT_VPS)
			{
				ASSERT_PARSER(nalu_len,MAX_VPS_LEN);
				memcpy(vps_buf_,buf + parse_offset,nalu_len);
				vps_len_ = nalu_len;
				parse_offset += nalu_len;
				continue;
			}
		}else{
			nalu_type = buf[parse_offset]&0x1F;
		}
       //H265 以及 H264的SPS頭解析兼容
        if((av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265&&nalu_type ==e_H265_NAL_UNIT_SPS) || 
			av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H264&&nalu_type == e_H264_Frame_Type_Sps)
        {
            ASSERT_PARSER(nalu_len,MAX_PPS_LEN);
            memcpy(sps_buf_,buf + parse_offset,nalu_len);
            sps_len_ = nalu_len;
            parse_offset += nalu_len;

			if(width_ == 0 && sps_len_ > 0)
			{
				if(av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265)
					rtmpclient_h265_decode_sps((unsigned char *)sps_buf_, sps_len_, width_, height_);
				else
					rtmpclient_h264_decode_sps((unsigned char *)sps_buf_, sps_len_, width_, height_);
			}
            continue;
        }
		       //H265 以及 H264的PPS頭解析兼容
		else if((av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265&&nalu_type ==e_H265_NAL_UNIT_PPS) || 
			av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H264&&nalu_type == e_H264_Frame_Type_Pps)
        {
            memcpy(pps_buf_,buf + parse_offset,nalu_len);
            pps_len_ = nalu_len;
            parse_offset += nalu_len;
            continue;
        }

       //H265 以及 H264的I幀解析兼容
		else if((av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265&&nalu_type >=e_H265_NAL_UNIT_SLICE_BLA&&nalu_type <=e_H265_NAL_UNIT_SLICE_CRA ) || 
		av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H264&&nalu_type == e_H264_Frame_Type_Idr)
        {
			if(av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265)
			{
				memcpy(processbuf + processlen,nalu_head_,4);
				processlen += 4;
				memcpy(processbuf + processlen,vps_buf_,vps_len_);
				processlen += vps_len_;
			}
			.......
			//拷貝SPS和PPS以及Idr nalu
			......
			av_frame.u32VFrameType = EASY_SDK_VIDEO_FRAME_I;
            continue ;
        }
       //H265 以及 H264的P幀解析兼容
		else if((av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H265&&nalu_type >=e_H265_NAL_UNIT_SLICE_TRAIL_R&&nalu_type <=e_H265_NAL_UNIT_SLICE_TFD ) || 
			av_frame.u32AVFrameFlag == EASY_SDK_VIDEO_CODEC_H264&&nalu_type == e_H264_Frame_Type_Slice)
        {
            memcpy(processbuf + processlen,nalu_head_,4);
            processlen += 4;
            memcpy(processbuf + processlen,buf + parse_offset,nalu_len);
            processlen += nalu_len;
            parse_offset += nalu_len;

			av_frame.u32VFrameType = EASY_SDK_VIDEO_FRAME_P;
            continue ;
        }
        else
        {
            parse_offset += nalu_len;
            continue;
        }
    }

    av_frame.pBuffer = (uint8_t *)processbuf;
    av_frame.u32AVFrameLen = processlen;
    return 0;
}

至此，EasyRTMPClient對H264和H265的兼容適配就完成了，我們可以通過EasyRTMPClient拉取任意編碼格式爲H264或者H265的RTMP進行拉流，均能取得完整的視頻幀數據進行解碼和播放。

歡迎大家下載EasyPlayer測試播放支持H265的RTMP流：
https://github.com/EasyDSS/EasyPlayer-RTMP-Win
https://github.com/EasyDSS/EasyPlayerPro-Win

有任何技術問題，歡迎大家和我進行技術交流：
[email protected]

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