Exporting(TXT/CSV)/Reading .vxl files generated by Voxel Viewer

Karthik Rajagopal

Other Parts Discussed in Thread: OPT8241

In many application it may be required to capture the scene/stream from Voxel viewer. Here are some examples of such sitations...

Further analysis like standard deviation, median, FFT of data captured
Testing/Developing new algorithms on depth or Point cloud data
Visualization in a different software
Reconstruction of 3D mesh

The best way to do this would be to use voxelSDK and capture. This however required setting up voxelSDK to control the Hardware and catpure.

In cases where one likes to do this quickly can use the attached method, which doesn't involve setting up voxelSDK for control and capture, instead Voxel Viewer is used to capture/record the scene as such to .vxl file. This captured .vxl file can then be exported to various streams (.bin files) explained in the attache document.

Once extracted the .bin files can be read using simple computer programs as shown in the attached example codes(Python and C codes are given).

ExtractionOfCSVFromVoxelViewer.zip

over 9 years ago

Ashwini Subramanian over 9 years ago

Prodigy 120 points

Hi ,

Very useful information. Thank you for sharing.
I have a question.

When I tried to view the raw exported data from voxel viewer (using matlab), The ground plane seems to have an inclination.While in reality, our ground plane is flat. Any reasons as to what might cause this?

-Ashwini

Bharath Patil over 9 years ago in reply to Ashwini Subramanian

TI__Intellectual 2030 points

The camera was not particularly positioned exactly perpendicular to the wall. So, some inclination can be expected.

Regards

Ashwini Subramanian over 9 years ago in reply to Bharath Patil

Prodigy 120 points

Thank you Bharath. I will check that.

I had one more question in this regard-

When the depth data was observed along a single row, It exhibited a large variation in value. Our understanding is, when looking at a flat object, the 'DEPTH' data along a single row needs to be constant and the 'DISTANCE' must vary uniformly on either side about the center of the image. Is the assumption right here?if it is so, What causes the variation in depth along one row?

-Ashwini

Lena CHONG over 8 years ago in reply to Ashwini Subramanian

Prodigy 95 points

Hi,

Can you tell me where can I found the matlab program that allow me to view the raw exported data from voxel viewer as a jpg or other format ?

iii www over 8 years ago

Prodigy 60 points

HI,

Just used DpethCapture from voxelsdk-examples to get out.bin file in raw format.
Then try to use python file (above downloaded) to get csv.

the result is
ERROR: File size [307467] for file [out.bin] not a multiple of frame size [4800] X nQuantities [1]
Traceback (most recent call last):
File "vxnBin2CSVExtractor.py", line 147, in <module>
data=data.reshape(nFrames,deviceResolution[device][1],deviceResolution[device][0],nQuantities).swapaxes(-1,-3)
NameError: name 'nFrames' is not defined

Would you please help to find a solution?

Thanks

iii www over 8 years ago

Prodigy 60 points

Hi

Just use depthcapture from voxelsdk-examples to get Ambient.bin in raw format.

Tried to use python file (above downloaded) to get csv

the result is
ERROR: File size [307467] for file [Ambient.bin] not a multiple of frame size [4800] X nQuantities [1]
Traceback (most recent call last):
File "vxnBin2CSVExtractor.py", line 147, in <module>
data=data.reshape(nFrames,deviceResolution[device][1],deviceResolution[device][0],nQuantities).swapaxes(-1,-3)
NameError: name 'nFrames' is not defined

Would you please help to find a solution?

Thanks

Lena CHONG over 8 years ago in reply to iii www

Prodigy 95 points

I use the c program (vxnBin2CSVExtractor.cpp) to convert the bin file to csv file, it is ok. But please remember to change the values of NROWS, NCOLS, NFRAMES if necessary.

But after get the csv file, do you know how to convert it into image file (such as jpg file). I wrote a matlab program to do the conversion, but the output image consists of only some noise.

iii www over 8 years ago in reply to Lena CHONG

Prodigy 60 points

Do the file from depthcapture and that from voxel viewer share the same format?

you could try png format, which might be better

Lena CHONG over 8 years ago in reply to iii www

Prodigy 95 points

How to change the csv file to png format ?

iii www over 8 years ago in reply to iii www

Prodigy 60 points

The code need to be made minor modification.

240*320*8=614400

240*320*4=307200

but the file size is 614412 and 307212 respectively. 12 bytes more.

fread(frame, sizeof(float), NFRAMES*NCOLS*NROWS, inFile);
fprintf(csvFile,"%f,",frame[i][k][j]);

Any one who could give the detail of depth file format in detail?

Thanks

Lena CHONG over 8 years ago in reply to iii www

Prodigy 95 points

Anyone try to display the csv file as a image using opencv ?

JAGADEESH PADI over 8 years ago in reply to iii www

Prodigy 20 points

Hi,

The extra 12 bytes is due to the d->id(4 bytes) and timestamp(8 bytes).....

if you want to ignore the id and timestamp .....go to DepthCapture.cpp and comment the respective lines(283,284 incase of "depth").....

Now the sizes will surely match......

Dmitry Gringauz53811 over 8 years ago

Intellectual 300 points

Hi Karthik,

Information that describes how to extract specific data from binary files that have been extracted from the .vxl file is very useful, but....

We are trying to evaluate the sensor using the OPT8241 EVM. The evaluation involves running the EVM through its paces under different test scenarios, and collecting sensor output. For data collection, Voxel Viewer is very convenient.

However, given the amount of data that we are dealing with, it would be very convenient to have some sort of command line interface to the exporter. That would allow us to perform batch processing and batch conversions, rather than extracting individual bin files using the GUI application.

From what I can tell, Voxel Exporter does not accept any command-line arguments.

Is it possible to obtain the format of the .VXL file so that I can write my own exporter suitable for batch processing?

Thank you,

Dmitry.

Karthik Rajagopal over 8 years ago in reply to Dmitry Gringauz53811

TI__Prodigy 330 points

Hi Dmitry,

Have you explored voxellCLI?

github.com/.../Voxel-CLI

This should give you the command line interface. I will get back on the best way to do batch processing.

thanks

Karthik

Dmitry Gringauz53811 over 8 years ago in reply to Karthik Rajagopal

Intellectual 300 points

Hi Karthik,

Thank you very much for your response.

Yes, I have explored Voxel CLI, and am in the middle of taking it apart.

I noticed that Voxel CLI and Voxel Exporter do not produce data in the same format. Specifically, it appears that X and Y axis are reversed when I try to capture amplitude and phase data directly using Voxel CLI.

Can I get a bit more insight into how they two applications differ, and what, if any, data massaging is performed by Voxel Exporter?

From what can tell, it is the Voxel Exporter that introduces changes. I take a .VXL file captured by Voxel Viewer and convert it using Voxel CLI and Voxel Exporter, and I get different results. Same happens if I take .VXL file captured by Voxel CLI.

I can post specific examples, if you would like.

Best Regards,

Dmitry.

Anand Gadiyar over 8 years ago in reply to Dmitry Gringauz53811

TI__Genius 15005 points

Hi Dmitry,

We have an example program in VoxelSDK that demonstrates how to extract frames from a VXL (see Test/CameraSystemReadStreamTest).

This program can read a .vxl - it does not currently save frames to disk, but only prints the timestamp and frame size, but it can be adapted to do save frames with minor changes.

We will update this program shortly to add this feature - this should give you the command-line equivalent of VoxelExporter.

We will check the X,Y axis swap behavior - this might be due to a different convention followed by VoxelExporter.

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Exporting(TXT/CSV)/Reading .vxl files generated by Voxel Viewer