嵌入式監控【v4l2採集->vpu編碼->live555推流】

文章目錄

在上一博客中介紹了視頻監控的採用庫和相關架構，這篇博客作爲優化和補充，主要優化的地方爲由v4l2代替opencv的採集，由vpu編碼代替x264

介紹

應爲x264在arm a9開發版中佔用大量cpu資源，導致視頻卡頓，所以決定採用使用v4l2來採集uvc數據，使用vpu編碼。
開發版爲imx6q，版載有vpu/ipu,可以代替x264的軟算法，釋放cpu資源。

數據流圖

v4l2 -> yuyv -> yuv420 -> vpu -> h264
數據流驗證過程：

v4l2採集yuyv數據，寫入到文件，使用pyuv播放驗證
轉碼yuyv到yuv420後，寫入到文件，使用pyuv播放驗證
將yuv420文件使用vpu編碼爲h264後，使用live555推流，vlc遠程播放驗證

一、v4l2

此處爲了精簡採集uvc（usb video cam）的採集過程，直接使用v4l2採集，而沒有使用opencv，opencv採集的數據Mat(RGB)需要在二次轉化。

1.1 確定cam的輸出格式

攝象頭有兩種，一種是模組形式，他的輸出格式多爲MJPG，另一種是uvc形式，他的輸出格式爲yuyv(422).
如何判斷攝象頭類型？一般使用usb接口的攝象頭爲uvc，而內嵌到板子上的多爲MJPG，可以使用命令工具v4l2-ctl來判斷.

下面是我的usb 羅技攝象頭：

root@zjy-T440:~/workStation/crossGcc/vpu/mxc_vpu_test# v4l2-ctl -d /dev/video0 --all
Driver Info (not using libv4l2):
	Driver name   : uvcvideo
	Card type     : Integrated Camera: Integrated C
	Bus info      : usb-0000:00:14.0-8
	Driver version: 5.3.18
	Capabilities  : 0x84A00001
		Video Capture
		Metadata Capture
		Streaming
		Extended Pix Format
		Device Capabilities
	Device Caps   : 0x04200001
		Video Capture
		Streaming
		Extended Pix Format
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
	Width/Height      : 640/480
	Pixel Format      : 'YUYV'
	Field             : None
	Bytes per Line    : 1280
	Size Image        : 614400
	Colorspace        : sRGB
	Transfer Function : Default (maps to sRGB)
	YCbCr/HSV Encoding: Default (maps to ITU-R 601)
	Quantization      : Default (maps to Limited Range)
	Flags             : 
Crop Capability Video Capture:
	Bounds      : Left 0, Top 0, Width 640, Height 480
	Default     : Left 0, Top 0, Width 640, Height 480
	Pixel Aspect: 1/1
Selection: crop_default, Left 0, Top 0, Width 640, Height 480
Selection: crop_bounds, Left 0, Top 0, Width 640, Height 480
Streaming Parameters Video Capture:
	Capabilities     : timeperframe
	Frames per second: 30.000 (30/1)
	Read buffers     : 0
                     brightness 0x00980900 (int)    : min=0 max=255 step=1 default=128 value=128
                       contrast 0x00980901 (int)    : min=0 max=255 step=1 default=32 value=32
                     saturation 0x00980902 (int)    : min=0 max=100 step=1 default=64 value=64
                            hue 0x00980903 (int)    : min=-180 max=180 step=1 default=0 value=0
 white_balance_temperature_auto 0x0098090c (bool)   : default=1 value=1
                          gamma 0x00980910 (int)    : min=90 max=150 step=1 default=120 value=120
           power_line_frequency 0x00980918 (menu)   : min=0 max=2 default=1 value=1
      white_balance_temperature 0x0098091a (int)    : min=2800 max=6500 step=1 default=4000 value=4000 flags=inactive
                      sharpness 0x0098091b (int)    : min=0 max=7 step=1 default=2 value=2
         backlight_compensation 0x0098091c (int)    : min=0 max=2 step=1 default=1 value=1
                  exposure_auto 0x009a0901 (menu)   : min=0 max=3 default=3 value=3
              exposure_absolute 0x009a0902 (int)    : min=4 max=1250 step=1 default=166 value=166 flags=inactive
         exposure_auto_priority 0x009a0903 (bool)   : default=0 value=1

下面爲開發版攝象頭：

root@imx6qsabresd:/home# v4l2-ctl -d /dev/video2 --all
Driver Info (not using libv4l2):
	Driver name   : uvcvideo
	Card type     : USB Camera
	Bus info      : usb-ci_hdrc.1-1.2
	Driver version: 4.1.15
	Capabilities  : 0x84200001
		Video Capture
		Streaming
		Extended Pix Format
		Device Capabilities
	Device Caps   : 0x04200001
		Video Capture
		Streaming
		Extended Pix Format
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
	Width/Height  : 1280/720
	Pixel Format  : 'MJPG'
	Field         : None
	Bytes per Line: 0
	Size Image    : 1843200
	Colorspace    : SRGB
	Flags         : 
Crop Capability Video Capture:
	Bounds      : Left 0, Top 0, Width 1280, Height 720
	Default     : Left 0, Top 0, Width 1280, Height 720
	Pixel Aspect: 1/1
Selection: crop_default, Left 0, Top 0, Width 1280, Height 720
Selection: crop_bounds, Left 0, Top 0, Width 1280, Height 720
Streaming Parameters Video Capture:
	Capabilities     : timeperframe
	Frames per second: 30.000 (30/1)
	Read buffers     : 0
                     brightness (int)    : min=-64 max=64 step=1 default=0 value=0
                       contrast (int)    : min=0 max=100 step=1 default=50 value=50
                     saturation (int)    : min=0 max=100 step=1 default=50 value=50
                            hue (int)    : min=-180 max=180 step=1 default=0 value=0
 white_balance_temperature_auto (bool)   : default=1 value=1
                          gamma (int)    : min=100 max=500 step=1 default=300 value=300
           power_line_frequency (menu)   : min=0 max=2 default=1 value=1
      white_balance_temperature (int)    : min=2800 max=6500 step=10 default=4600 value=4600 flags=inactive
                      sharpness (int)    : min=0 max=100 step=1 default=50 value=50
         backlight_compensation (int)    : min=0 max=2 step=1 default=0 value=0
                  exposure_auto (menu)   : min=0 max=3 default=3 value=3
              exposure_absolute (int)    : min=50 max=10000 step=1 default=166 value=166 flags=inactive
         exposure_auto_priority (bool)   : default=0 value=1
                   pan_absolute (int)    : min=-57600 max=57600 step=3600 default=0 value=0
                  tilt_absolute (int)    : min=-43200 max=43200 step=3600 default=0 value=0
                  zoom_absolute (int)    : min=0 max=3 step=1 default=0 value=0
                     brightness (int)    : min=-64 max=64 step=1 default=0 value=0
                       contrast (int)    : min=0 max=100 step=1 default=50 value=50
                     saturation (int)    : min=0 max=100 step=1 default=50 value=50
                            hue (int)    : min=-180 max=180 step=1 default=0 value=0
 white_balance_temperature_auto (bool)   : default=1 value=1
                          gamma (int)    : min=100 max=500 step=1 default=300 value=300
           power_line_frequency (menu)   : min=0 max=2 default=1 value=1
      white_balance_temperature (int)    : min=2800 max=6500 step=10 default=4600 value=4600 flags=inactive
                      sharpness (int)    : min=0 max=100 step=1 default=50 value=50
         backlight_compensation (int)    : min=0 max=2 step=1 default=0 value=0

MJPG格式的cam，輸出的jpeg圖像，可以直接用來顯示，直接一幀接着一幀就可以構成視頻，但是如果想轉化爲h264 就需要先解碼爲yuv，再編碼h264，所以此處採用uvc攝象頭開發，uvc採集到的數據爲yuyv。

1.2 YUYV 轉 YUV420

爲了使用vpu硬編碼，需要轉化爲vpu的輸入格式yuv420。
自行研究YUV格式，轉換直接上代碼：

 88 int YUV422To420(unsigned char yuv422[], unsigned char yuv420[], int width, int height)
 89 {
 90 
 91        int ynum=width*height;
 92        int i,j,k=0;
 93     //得到Y分量  
 94        for(i=0;i<ynum;i++){
 95            yuv420[i]=yuv422[i*2];
 96        }
 97     //得到U分量  
 98        for(i=0;i<height;i++){
 99            if((i%2)!=0)continue;
100            for(j=0;j<(width/2);j++){
101                if((4*j+1)>(2*width))break;
102                yuv420[ynum+k*2*width/4+j]=yuv422[i*2*width+4*j+1];
103                        }
104             k++;
105        }
106        k=0;
107     //得到V分量  
108        for(i=0;i<height;i++){
109            if((i%2)==0)continue;
110            for(j=0;j<(width/2);j++){
111                if((4*j+3)>(2*width))break;
112                yuv420[ynum+ynum/4+k*2*width/4+j]=yuv422[i*2*width+4*j+3];
113 
114            }
115             k++;
116        }
117 
118        return 1;
119 }
需要注意：YUYV和YUV420的幀大小計算
YUYV：h*w*2
YUV420: h*w*3/2
size(YUV420) = size(YUYV)*3/4
如果幀大小差異被忽略，導致花屏。

1.3 播放採集到的yuv420數據

研究YUV編碼，一定用到一個播放YUV的播放軟件pYUV，在linux可以安裝使用。

size: 採集攝象頭的幀大小
Color space: 色域空間，yuv
subsampling:由uvc直接採集到的是422，可自行轉換420
interleaved：隔行掃描，經過轉換420後的yuv不需要鉤選
此處有個概念容易混淆，掃描方式和存儲方式，此處的interleaved爲存儲方式，和v4l2中的fmt.pix.field = V4L2_FIELD_NONE不是同一個概念，v4l2中設置的是掃描方式。

二、vpu硬編碼

nxp官方文檔有提供imx6 vpu相關的文檔：VPU_API_RM_L3.0.35_1.1.0.pdf
3.3.1.2
Encoder Operation Flow
To encode a bitstream, the application completes the following steps:

Call vpu_Init() to initialize the VPU.
Open a encoder instance by using vpu_EncOpen().
Before starting a picture encoder operation, get crucial parameters for encoder operations such as required frame buffer
size by using vpu_EncGetInitialInfo().
By using the returned frame buffer requirement, allocate size of frame buffers and convey this information to the VPU
by using vpu_EncRegisterFrameBuffer().
Generate high-level header syntax by using vpu_EncGiveCommand().
Start picture encoder operation picture-by-picture by using vpu_EncStartOneFrame().
Wait the completion of picture encoder operation interrupt event.
After encoding a frame is complete, check the results of encoder operation by using vpu_EncGetOutputInfo().
If there are more frames to encode, go to Step 4. Otherwise, go to the next step.
Terminate the sequence operation by closing the instance using vpu_EncClose().
Call vpu_UnInit() to release the system resources.
The encoder operation flow is shown in figure below.

4.4.2.2
Encode Stream from Camera Captured Data
The application should complete the following steps to encode streams from camera captured data:

Call vpu_Init() to initialize the VPU. If there are multi-instances supported in this application, this function only needs
to be called once.
Open a encoder instance using vpu_EncOpen(). Call IOGetPhyMem() to input encop.bitstreamBuffer for the physical
continuous bitstream buffer before opening the instance. Call IOGetVirtMem() to get the corresponding virtual
address of the bitstream buffer, then fill the bitstream to this address in user space. If rotation is enabled and the
rotation angle is 90° or 270°, the picture width and height must be swapped.
If rotation is enabled, give commands ENABLE_ROTATION and SET_ROTATION_ANGLE. If mirror is enabled,
give commands ENABLE_MIRRORING and SET_MIRROR_DIRECTION.
Get crucial parameters for encoder operations such as required frame buffer size, and so on using
vpu_EncGetInitialInfo().
Using the frame buffer requirement returned from vpu_DecGetInitialInfo(), allocate the proper size of the frame
buffers and notify the VPU using vpu_EncRegisterFrameBuffer(). The requested frame buffer for the source frame in
PATH_V4L2 to encode camera captured data is as follows:
• Allocate the minFrameBufferCount frame buffers by calling IOGetPhyMem() and register them to the VPU for
encoder using vpu_EncRegisterFrameBuffer().
• Another frame buffer is needed for the source frame buffer. Call v4l_capture_setup() to open the v4l device for
camera and request v4l buffers. In this example, three v4l buffers are allocated. Call v4l_start_capturing() to
start camera capture. Pass the dequeued v4l buffer address by calling v4l_get_capture_data() as encoder source
frame in each picture encoder, then no need to memory transfer for performance improvement.
Generate the high-level header syntaxes using vpu_EncGiveCommand().
Start picture encoder operation picture-by-picture using vpu_EncStartOneFrame(). Pass dequeued v4l buffer address
by calling v4l_get_capture_data() as the encoder source frame before each picture encoder is started.
Wait for the completion of picture decoder operation interrupt event calling vpu_WaitforInt(). Use vpu_IsBusy() to
check if the VPU is busy. If the VPU is not busy, go to the next step; otherwise, wait again.
After encoding a frame is complete, check the results of encoder operation using vpu_EncGetOutputInfo(). After the
output information is received, call v4l_put_capture_data() to the VIDIOC_QBUF v4l buffer for the next capture
usage.
If there are more frames to encode, go to Step 7; otherwise, go to the next step.
Terminate the sequence operation by closing the instance using vpu_DecClose(). Make sure
vpu_DecGetOutputInfo() is called for each corresponding vpu_DecStartOneFrame() call before closing the instance
although the last output information may be not useful.
Free all allocated memory and v4l resource using IOFreePhyMem() and IOFreeVirtMem(). Call
v4l_stop_capturing() to stop capture.
Call vpu_UnInit() to release the system resources. If there are multi-instances supported in this application, this
function only needs to be called once.

文檔對vpu編解碼都將的很清楚，並且開發版附帶的資料中有mxc_vpu_test.out 的源碼和幫助文檔。

2.1 使用mxc_vpu_test.out 硬件編碼h264

開發版內自帶vpu測試工具及源碼：mxc_vpu_test.out，先使用該工具轉碼yuv420爲h264，驗證數據正確性。

root@imx6qsabresd:/# cd /unit_tests/
root@imx6qsabresd:/unit_tests# ./mxc_vpu_test.out -E "-i out.yuv -w 624 -h 416 -f 2 -o file.264 -t 0"
root@imx6qsabresd:/home# ./mxc_vpu_test.out 
[INFO]	
Usage: ./mxc_vpu_test.out -D "<decode options>" -E "<encode options>" -L "<loopback options>" -C <config file> -T "<transcode options>" -H display this help 
 
decode options 
   -i <input file> Read input from file 
 	If no input file is specified, default is network 
   -o <output file> Write output to file 
 	If no output is specified, default is LCD 
   -x <output method> output mode V4l2(0) or IPU lib(1) 
         0 - V4L2 of FG device, 1 - IPU lib path 
         2 - G2D (available for Android only) 
         Other value means V4L2 with other video node
         16 - /dev/video16, 17 - /dev/video17, and so on 
   -f <format> 0 - MPEG4, 1 - H.263, 2 - H.264, 3 - VC1, 
 	4 - MPEG2, 5 - DIV3, 6 - RV, 7 - MJPG, 
         8 - AVS, 9 - VP8
 	If no format specified, default is 0 (MPEG4) 
   -l <mp4Class / h264 type> 
         When 'f' flag is 0 (MPEG4), it is mp4 class type. 
         0 - MPEG4, 1 - DIVX 5.0 or higher, 2 - XVID, 5 - DIVX4.0 
         When 'f' flag is 2 (H.264), it is h264 type. 
         0 - normal H.264(AVC), 1 - MVC 
   -p <port number> UDP port number to bind 
 	If no port number is secified, 5555 is used 
   -c <count> Number of frames to decode 
   -d <deblocking> Enable deblock - 1. enabled 
 	default deblock is disabled (0). 
   -e <dering> Enable dering - 1. enabled 
 	default dering is disabled (0). 
   -r <rotation angle> 0, 90, 180, 270 
 	default rotation is disabled (0) 
   -m <mirror direction> 0, 1, 2, 3 
 	default no mirroring (0) 
   -u <ipu/gpu rotation> Using IPU/GPU rotation for display - 1. IPU/GPU rotation 
         default is VPU rotation(0).
         This flag is effective when 'r' flag is specified.
   -v <vdi motion> set IPU VDI motion algorithm l, m, h.
 	default is m-medium. 
   -w <width> display picture width 
 	default is source picture width. 
   -h <height> display picture height 
 	default is source picture height 
   -j <left offset> display picture left offset 
 	default is 0. 
   -k <top offset> display picture top offset 
 	default is 0 
   -a <frame rate> display framerate 
 	default is 30 
   -t <chromaInterleave> CbCr interleaved 
         default is interleave(1). 
   -s <prescan/bs_mode> Enable prescan in decoding on i.mx5x - 1. enabled 
         default is disabled. Bitstream mode in decoding on i.mx6  
         0. Normal mode, 1. Rollback mode 
         default is enabled. 
   -y <maptype> Map type for GDI interface 
         0 - Linear frame map, 1 - frame MB map, 2 - field MB map 
         default is 0. 
 
encode options 
   -i <input file> Read input from file (yuv) 
 	If no input file specified, default is camera 
   -x <input method> input mode V4L2 with video node 
         0 - /dev/video0, 1 - /dev/video1, and so on 
   -o <output file> Write output to file 
 	This option will be ignored if 'n' is specified 
 	If no output is specified, def files are created 
   -n <ip address> Send output to this IP address 
   -p <port number> UDP port number at server 
 	If no port number is secified, 5555 is used 
   -f <format> 0 - MPEG4, 1 - H.263, 2 - H.264, 7 - MJPG 
 	If no format specified, default is 0 (MPEG4) 
   -l <h264 type> 0 - normal H.264(AVC), 1 - MVC
   -c <count> Number of frames to encode 
   -r <rotation angle> 0, 90, 180, 270 
 	default rotation is disabled (0) 
   -m <mirror direction> 0, 1, 2, 3 
 	default no mirroring (0) 
   -w <width> capture image width 
 	default is 176. 
   -h <height>capture image height 
 	default is 144 
   -b <bitrate in kbps> 
 	default is auto (0) 
   -g <gop size> 
 	default is 0 
   -t <chromaInterleave> CbCr interleaved 
         default is interleave(1). 
   -q <quantization parameter> 
 	default is 20 
   -a <frame rate> capture/encode framerate 
 	default is 30 
 
loopback options 
   -x <input method> input mode V4L2 with video node 
         0 - /dev/video0, 1 - /dev/video1, and so on 
   -f <format> 0 - MPEG4, 1 - H.263, 2 - H.264, 7 - MJPG 
 	If no format specified, default is 0 (MPEG4) 
   -w <width> capture image width 
 	default is 176. 
   -h <height>capture image height 
 	default is 144 
   -t <chromaInterleave> CbCr interleaved 
         default is interleave(1). 
   -a <frame rate> capture/encode/display framerate 
 	default is 30 
 
transcode options, encoder set to h264 720p now 
   -i <input file> Read input from file 
         If no input file is specified, default is network 
   -o <output file> Write output to file 
         If no output is specified, default is LCD 
   -x <output method> V4l2(0) or IPU lib(1) 
   -f <format> 0 - MPEG4, 1 - H.263, 2 - H.264, 3 - VC1, 
         4 - MPEG2, 5 - DIV3, 6 - RV, 7 - MJPG, 
         8 - AVS, 9 - VP8
         If no format specified, default is 0 (MPEG4) 
   -l <mp4Class / h264 type> 
         When 'f' flag is 0 (MPEG4), it is mp4 class type. 
         0 - MPEG4, 1 - DIVX 5.0 or higher, 2 - XVID, 5 - DIVX4.0 
         When 'f' flag is 2 (H.264), it is h264 type. 
         0 - normal H.264(AVC), 1 - MVC 
   -p <port number> UDP port number to bind 
         If no port number is secified, 5555 is used 
   -c <count> Number of frames to decode 
   -d <deblocking> Enable deblock - 1. enabled 
         default deblock is disabled (0). 
   -e <dering> Enable dering - 1. enabled 
         default dering is disabled (0). 
   -r <rotation angle> 0, 90, 180, 270 
         default rotation is disabled (0) 
   -m <mirror direction> 0, 1, 2, 3 
         default no mirroring (0) 
   -u <ipu rotation> Using IPU rotation for display - 1. IPU rotation 
         default is VPU rotation(0).
         This flag is effective when 'r' flag is specified.
   -v <vdi motion> set IPU VDI motion algorithm l, m, h.
         default is m-medium. 
   -w <width> display picture width 
         default is source picture width. 
   -h <height> display picture height 
         default is source picture height 
   -j <left offset> display picture left offset 
         default is 0. 
   -k <top offset> display picture top offset 
         default is 0 
   -a <frame rate> display framerate 
         default is 30 
   -t <chromaInterleave> CbCr interleaved 
         default is interleave(1). 
   -s <prescan/bs_mode> Enable prescan in decoding on i.mx5x - 1. enabled 
         default is disabled. Bitstream mode in decoding on i.mx6  
         0. Normal mode, 1. Rollback mode 
         default is enabled. 
   -y <maptype> Map type for GDI interface 
         0 - Linear frame map, 1 - frame MB map, 2 - field MB map 
   -q <quantization parameter> 
 	default is 20 
 
config file - Use config file for specifying options

./mxc_vpu_test.out -E “-i out.yuv -w 624 -h 416 -f 2 -o file.264 -t 0”
-E 編碼操作
-i 輸入的yuv文件
-w -h 視頻分辨率
-f 轉碼爲h264
-o 輸出文件名
-t 是否隔行存儲
轉碼後生成file.h264，此時可以直接使用live555推流播放了。

三、使用live555MediaServer推流

此處參考上篇博文，使用移植後的live555MediaServer直接推流測試。

root@imx6qsabresd:/home# ./live555MediaServer 
LIVE555 Media Server
	version 0.99 (LIVE555 Streaming Media library version 2020.01.28).
Play streams from this server using the URL
	rtsp://192.168.2.11/<filename>
where <filename> is a file present in the current directory.
Each file's type is inferred from its name suffix:
	".264" => a H.264 Video Elementary Stream file
	".265" => a H.265 Video Elementary Stream file
	".aac" => an AAC Audio (ADTS format) file
	".ac3" => an AC-3 Audio file
	".amr" => an AMR Audio file
	".dv" => a DV Video file
	".m4e" => a MPEG-4 Video Elementary Stream file
	".mkv" => a Matroska audio+video+(optional)subtitles file
	".mp3" => a MPEG-1 or 2 Audio file
	".mpg" => a MPEG-1 or 2 Program Stream (audio+video) file
	".ogg" or ".ogv" or ".opus" => an Ogg audio and/or video file
	".ts" => a MPEG Transport Stream file
		(a ".tsx" index file - if present - provides server 'trick play' support)
	".vob" => a VOB (MPEG-2 video with AC-3 audio) file
	".wav" => a WAV Audio file
	".webm" => a WebM audio(Vorbis)+video(VP8) file
See http://www.live555.com/mediaServer/ for additional documentation.
(We use port 80 for optional RTSP-over-HTTP tunneling, or for HTTP live streaming (for indexed Transport Stream files only).)

推流後可以直接使用vlc等rtsp播放軟件，播放rtsp://192.168.2.11/file.264 文件。

總結

最後以上數據鏈路打通後，開始着手整合代碼。
源碼整理中，敬請期待。

嵌入式監控【v4l2採集->vpu編碼->live555推流】

嵌入式監控【v4l2採集->vpu編碼->live555推流】

文章目錄

介紹

數據流圖

一、v4l2

1.1 確定cam的輸出格式

1.2 YUYV 轉 YUV420

1.3 播放採集到的yuv420數據

二、vpu硬編碼

2.1 使用mxc_vpu_test.out 硬件編碼h264

三、使用live555MediaServer推流

總結

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嵌入式監控【v4l2採集->vpu編碼->live555推流】

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