[Elphel-support] 答复: 答复: 答复: 答复: 答复: sync stereo with lidar

Winston Zhang winston.zhang at blacksesame.com.cn
Wed Mar 7 17:32:15 PST 2018 

Hi, Andrey
      I met a new question. I set ‘Color’ parameter with the five(it could get the jp4 format image)on one camera, and this camera image format was converted. But when I set the other one, this camera image format was not converted. Please help me test for it.
      Another question
      What is the raw jp4 format image with 100% compression bit wide? I read it and the result show the bit wide is uint8. But you web shows that the bit wide is 12bit.



Best Regrad!
Yicheng-Zhang
Email:  winston.zhang at blacksesame.com.cn
Teil:    18516291005
Addr:   707 room, 7th floor, building 4th, No.1761, Zhangdong road, Pudong area

发件人: Andrey Filippov [mailto:andrey at elphel.com]
发送时间: 2018年3月7日 星期三 14:20
收件人: Winston Zhang <winston.zhang at blacksesame.com.cn>
抄送: Elphel Support <support-list at support.elphel.com>; Elphel Sales | Olga Filippova <sales at elphel.com>; Tao Zhang <tao.zhang at blacksesame.com.cn>; Qun Gu <qun.gu at blacksesame.com>; Pioneer Li <pioneer.li at blacksesame.com.cn>
主题: Re: 答复: [Elphel-support] 答复: 答复: 答复: sync stereo with lidar

Winston,

Quad quality 5MPix  JP4 image should be 1.8-2MB size, yours is <500KB. For image processing I recommend using compression quality 97-98% as we do.

The sensor uses Bayer mosaic, so sensor output has 5 MPix, not 3*5MPix - the color appears during de-mosaic process. JP4 saves pixels as they come out from the sensor (raw), color interpolation should be done during processing. Here are images that illustrate JP4:

https://community.elphel.com/jp4/jp4demo.php

For your application I do not recommend converting to color. When using a simple viewer there will be not much advantage over the camera JPEG output. For image matching you may first use just green channel (green pixels are in a checkerboard pattern), add color separately. When we process such images we apply different lens correction for each color and only mix them after aberration correction. Using just green is the simplest way to process.

Andrey



---- On Tue, 06 Mar 2018 21:12:18 -0800 Winston Zhang<winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>> wrote ----
Hi, Andrey
      Please take a look at attachments. The rawJP4 image was captured from the camera, and I converted it and got the result as result.png. But when I magnified this image, I found some block included 16x16 grid. I did not know the reason. Can you explain it.(The grid image please take look at grid.png).
      Another question is that the result image is single channel but not three channel like as rgb-channel. But if I converted it through the jp4viewer, the result is color image. Why? How do you do this?


Best Regrad!
Yicheng-Zhang
Email:  winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>
Teil:    18516291005
Addr:   707 room, 7th floor, building 4th, No.1761, Zhangdong road, Pudong area

发件人: Andrey Filippov [mailto:andrey at elphel.com<mailto:andrey at elphel.com>]
发送时间: 2018年3月6日 星期二 15:58
收件人: Winston Zhang <winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>>
抄送: Elphel Support <support-list at support.elphel.com<mailto:support-list at support.elphel.com>>; Elphel Sales | Olga Filippova <sales at elphel.com<mailto:sales at elphel.com>>; Tao Zhang <tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>>; Qun Gu <qun.gu at blacksesame.com<mailto:qun.gu at blacksesame.com>>; Pioneer Li <pioneer.li at blacksesame.com.cn<mailto:pioneer.li at blacksesame.com.cn>>
主题: Re: [Elphel-support] 答复: 答复: 答复: sync stereo with lidar

Winston,

There are several ways how to set the JP4 mode:

1) set it from the camera GUI (click Camera Control Interface port #), then click camera icon (top left), then "More details" and select color mode to jp4.
2) set with "Parameter Editor": follow Parameter Editor from the home page, check bit 2 - "Image color, quality ..." -> "View/Edit Current", set "COLOR: line New value to 5 (it is jp4) and click "Apply" button.
3) make this mode default(after either 1) or 2) )- save current settings in "Parameter Editor" (previous page) - Press topmost "Save" button (you may later change comments for the settings). Then you may set saved settings as default (select it and then press "Update default"). Next time you start the camera it will use these settings.
Then repeat the same for the other channel.

Andrey

---- On Mon, 05 Mar 2018 01:46:22 -0800 Winston Zhang<winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>> wrote ----
Hello, Andrey,

            I need information inside camera. How can I get jp4 format image? What is the image default format? If I try the command line “wget http://192.168.0.9:2323/img -O filename.jp4<http://192.168.0.9:2323/img%20-O%20filename.jp4>”, Can I get the jp4 format Image?

            Thank you!
”



Best Regrad!
Yicheng-Zhang
Email:  winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>
Teil:    18516291005
Addr:   707 room, 7th floor, building 4th, No.1761, Zhangdong road, Pudong area

发件人: Andrey Filippov [mailto:andrey at elphel.com<mailto:andrey at elphel.com>]
发送时间: 2018年3月2日 星期五 10:47
收件人: Winston Zhang <winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>>; Elphel Support <support-list at support.elphel.com<mailto:support-list at support.elphel.com>>
抄送: Tao Zhang <tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>>; Elphel Support <support-list at support.elphel.com<mailto:support-list at support.elphel.com>>; Elphel Sales | Olga Filippova <sales at elphel.com<mailto:sales at elphel.com>>; Qun Gu <qun.gu at blacksesame.com<mailto:qun.gu at blacksesame.com>>; Pioneer Li <pioneer.li at blacksesame.com.cn<mailto:pioneer.li at blacksesame.com.cn>>
主题: Re: 答复: 答复: [Elphel-support] sync stereo with lidar

Hello Winston,

Do you need information inside camera or for post-processing on a host PC?

Sensor has 12 bits, and using JP4 format (https://wiki.elphel.com/wiki/JP4) you can restore image data with the error less than the pixel shot noise

Here is an article explaining why it is so:

http://linuxdevices.io/how-many-bits-are-really-needed-in-the-image-pixels/

With ImageJ plugin you can convert JP4 file to 32-bit TIFF

Andrey







---- On Thu, 01 Mar 2018 17:17:14 -0800 Winston Zhang<winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>> wrote ----
Hello,
      Does this camera image pixel have 10 bit of the single channel? And how can I get it? Thank you.



Best Regrad!
Yicheng-Zhang
Email:  winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>
Teil:    18516291005
Addr:   707 room, 7th floor, building 4th, No.1761, Zhangdong road, Pudong area

发件人: Andrey Filippov [mailto:andrey at elphel.com<mailto:andrey at elphel.com>]
发送时间: 2018年2月1日 星期四 13:49
收件人: Tao Zhang <tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>>
抄送: Elphel Support <support-list at support.elphel.com<mailto:support-list at support.elphel.com>>; Elphel Sales | Olga Filippova <sales at elphel.com<mailto:sales at elphel.com>>; Winston Zhang <winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>>; Qun Gu <qun.gu at blacksesame.com<mailto:qun.gu at blacksesame.com>>; Pioneer Li <pioneer.li at blacksesame.com.cn<mailto:pioneer.li at blacksesame.com.cn>>
主题: Re: 答复: [Elphel-support] sync stereo with lidar

Tao,

USB GPS does not have 1pps signal (only serial has), precise synchronization is not possible that way. GPS time is available in each frame Exif header data - recorded on internal SSD or sent over the network.

The high resolution time stamps (1 microsecond step) are also provided with each  image, but they use internal camera clock, not the GPS.

This is why for precise synchronization you need to use event logger- it records events and timestamps them using the same clock.

If you had serial GPS with https://wiki.elphel.com/wiki/103696 - you would still need to use event logger - with serial GPS there will be 1 PPS precise GPS events timestamped with camera internal clock, and the images timestamped wit the same clock - that provides absolute calibration for the camera internal clock.

Without serial GPS you may use pulses from the LIDAR (it is possible to provide LIDAR pulse number over the Ethernet in addition to the precise time over the sync cable)

Andrey

---- On Wed, 31 Jan 2018 18:12:00 -0800 Tao Zhang<tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>> wrote ----
Hi Andrey,
We prefer to use GPS to synchronize stereo with lidar.
Where do those images that contain timestamp store in internal disk? Can we get it from ethernet continuously?

Tao Zhang
章   涛

发件人: Andrey Filippov [mailto:andrey at elphel.com<mailto:andrey at elphel.com>]
发送时间: 2018年2月1日 1:52
收件人: Tao Zhang <tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>>
抄送: Elphel Support <support-list at support.elphel.com<mailto:support-list at support.elphel.com>>; Elphel Sales | Olga Filippova <sales at elphel.com<mailto:sales at elphel.com>>; Winston Zhang <winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>>; Qun Gu <qun.gu at blacksesame.com<mailto:qun.gu at blacksesame.com>>; Pioneer Li <pioneer.li at blacksesame.com.cn<mailto:pioneer.li at blacksesame.com.cn>>
主题: Re: [Elphel-support] sync stereo with lidar

Hi Tao,

There are several ways how to do that:
One method would be be to get camera sync pulses for each frame and use external electronics to match with the LIDAR.
Another is to provide pulses from the LIDAR to the camera and record them with in-camera FPGA logger (https://wiki.elphel.com/wiki/Event_logger), together with the camera frames. In this case the camera will record 2 types of events:
 -  image frames with the frame number, frame timestamp that will be recorded in each frame header as Exif.
 - external pulse
Each of the two types of events will have a logger timestamp (with microsecond resolution). Logger can also record GPS timestamps (for serial GPS only and 103696 board -https://wiki.elphel.com/wiki/103696) and IMU (https://wiki.elphel.com/wiki/103695), in your case there are just 2 types listed above.

Both output (+5V pulses) and input (3.3V..5.0V) are available through the 2.5mm audio connector (marked "sync" https://wiki.elphel.com/images/0/0f/NC393-CS_marked_ports.jpeg ), here is the pinout and description: https://wiki.elphel.com/wiki/103891 .

Andrey

---- On Wed, 31 Jan 2018 04:19:04 -0800 Tao Zhang<tao.zhang at blacksesame.com.cn<mailto:tao.zhang at blacksesame.com.cn>> wrote ----
Hi Andrey,
We are going to use stereo with lidar. We need to sync stereo frames with lidar point cloud. Do you have any suggestions on how to do that?
Thanks.

Tao Zhang
章   涛

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