ROS2 package with messages for the ffmpeg_image_transport

This package has definitions for ROS2 messages of the ffmpeg image transport. See the ffmpeg_encoder_decoder package for more details about the encoding and decoding process, and the meaning of the encoding message field.

The encoding message field is a string with semicolon-separated tokens that indicate the codec (first token) and the image formats used at various stages of the encoding process: codec;av_source_pixel_format;cv_bridge_target_format;ros_encoding.

• ros_encoding is the pixel format used by the original ROS message that was passed to the ffmpeg_encoder_decoder module, e.g. bgr8. This token allows the decoder later to restore the original message format if desired.
• cv_bridge_target_format is the pixel format that the cv_bridge converts the ros_encoding into. This is typically a format that is more suited for ffmpeg compression.
• av_source_pixel_format is the pixel format that libswscale converts the cv_bridge_target_format into. This token uses libav convention (e.g. yuv420p), and denotes the pixel format that is fed into the libav encoder.
• codec is the codec used for ultimately encoding the packet, e.g. h264, hevc etc. Follows libav convention.

The encoding process is best understood by looking at the ffmpeg_encoder_decoder documentation.

License

This package is released under the Apache-2 license.