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Overview

theora_image_transport is a plugin package for image_transport. It enables any node using image_transport classes to publish and subscribe to image topics compressed over the wire using the Theora video codec.

theora_image_transport only works with 8-bit color or grayscale images.

Before reading this page, make sure you understand the image_transport package

Tutorials

See image_transport/Tutorials for general instruction on using image_transport.

ROS API

Publisher plugin

Published Topics

<base topic>/theora (theora_image_transport/Packet)

• Theora transport subtopic

Parameters

Reconfigurable parameters

All publisher parameters are dynamically reconfigurable per-topic. See dynamic_reconfigure for details on dynamically reconfigurable parameters.

<base topic>/theora/optimize_for (int, default: Quality (1))

• Controls whether to use constant bitrate (CBR) encoding, aiming for ~theora/target_bitrate; or variable bitrate (VBR) encoding, aiming for ~theora/quality. Values are Bitrate (0) and Quality (1).

<base topic>/theora/target_bitrate (int, default: 800000)

• Target bitrate. Used if optimize_for is set to Bitrate.

<base topic>/theora/quality (int, default: 31)

• Encoding quality level, in the range [0, 63]. Used if optimize_for is set to Quality.

<base topic>/theora/keyframe_frequency (int, default: 64)

• Maximum distance between key frames. If set to 1, every frame is a keyframe.

Subscriber plugin

Subscribed Topics

<base topic>/theora (theora_image_transport/Packet)

• Theora transport subtopic

Parameters

Reconfigurable parameters

All subscriber parameters are dynamically reconfigurable per-node.

~theora/post_processing_level (int, default: 0)

• Post-processing level. Higher values can improve the appearance of the decoded images at the cost of more CPU.

Nodes

ogg_saver

ogg_saver listens to the Theora transport packets associated with an image topic and saves them out to a .ogv file for later playback with tools like VLC or mplayer. Since Theora does not currently support variable frame rate videos the saved file will have a speed of one frame per second.

Subscribed Topics

<image>/theora (theora_image_transport/Packet)

• The topic containing the Theora packet stream. Note that you remap the base topic image, just as with other image consumers like image_view.

DEPRECATED

stream (theora_image_transport/Packet)

• The topic containing the Theora packet stream.

Usage

$ rosrun theora_image_transport ogg_saver image:=<base_topic> [output_file.ogv]