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difference between compressed_image and compressed_depth_image

asked 2013-03-19 15:48:28 -0500

AdrianPeng gravatar image

Hi there,

I am wondering what's difference between compressed_image and compressed_depth_image?

If I want to compress raw image as much as possible for high resolution wireless video streaming, which one should I choose?

Thanks for any help in advance!

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answered 2013-03-20 19:13:35 -0500

These message types are for sending fairly different types of messages between nodes:

  • compressed_image - standard color images
    • 3-channel (RGB), 8-bit
    • compressed using either JPG or PNG formats, with user-specified settings
  • compressed_depth_image - depth image (e.g. from kinect or stereo cameras)
    • 1-channel, either 32-bit float or 16-bit integer
    • compressed using PNG format

Your application sounds like it involves standard (not "3D") video data, so I would choose the compressed_image format. See this tutorial for examples of how to adjust the compression "quality" to achieve your desired performance.

As far as I know, though, the image_transport package hides the details of the specific transports from your application. You shouldn't have to interface with a compressed_image directly. The image_transport exposes images on both sides as standard Image messages. See the examples at these tutorials. You can toggle between different methods by setting the ~image_transport parameter to see the effect on performance. In particular, you may want to look into the theora streaming-video method.

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The usually used compressing algorithms don't work with a depth image (32-bit float or 16-bit integer). This is the reason for this spacial plugin.

MichaelKorn gravatar image MichaelKorn  ( 2013-03-21 05:23:54 -0500 )edit

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Asked: 2013-03-19 15:48:28 -0500

Seen: 861 times

Last updated: Mar 20 '13