Conventional services over Ethernet, LAN (Local Area Network), wireless and mobile network and mobile. It finds the applications in interactive or serial storage on optical and magnetic storage devices, DVDs (Digital Video Disk). The new H.264/AVC & Enhanced version H.265 standard is designed to provide a technical solution, the H.265 is the latest video compression technique in which 50% of bit rate is saved more than H.264 and broad range of applications, including broadcast over cable, satellite, cable modem, and terrestrial. The time has arrived to see what has been accomplished. The work has been stimulating, intense, dynamic, and all-consuming for those of us most deeply involved in its design. Work on the emerging " Advanced Video Coding " (AVC) standard now known as ITU-T(International Telecommunication Union) Recommendation H.264 and as ISO 14496(International Organization For Standards) (MPEG-4) Part 10 has dominated the video coding standardization community. MPEG1 (Motion Picture Expert Group), MPEG2, MPEG4, H.261, H.263, H.264 are the ancestors of H.265. Only the residual information is transmitted using the technique called as block based motion estimation and motion compensation. Video compression algorithms take the advantage of this fact. The successive images are highly correlated with each other. This step may become optional when automatic topic remapping is implemented.Video is the sequence of images played with respect to time. This is the only change in the code that will have to be done to reduce any potential namespace conflicts. For example, the node that is subscribing to /camera/image_raw in the cloud should now listen for /camera/image_raw/cloud. The node on the cloud that is expecting to receive the raw images should have the listener’s topic name changed from to /cloud. The compression standard supports various profiles that define the compression ratio and complexity of the implementation. compressed will default to JPEG compression, so the ROS 2 parameter of /compressed/format needs to be changed to ‘png’. Valid options for the 2nd element of a given tuple are h264, theora, or compressed. Repeat this step for any/all topics that should be compressed, and add each topic as a separate tuple in the stream_topics list. For the /camera/image_raw example, if H.264 was desired, the argument to fogros2.CloudNode would be stream_topics=. H.264/5 are even the type of files you watch when you are watching movies at the movie theater. The stream_topics argument is a list of tuples, where the first argument in the tuple is the topic name, and the second argument is the transport/compression type. H.264, H.265 and VP8/VP9/AV1/WebM are video in the way that we normally think of video. When modifying an existing launch file, and in Step 4 of this guide, add a stream_topics argument to the fogros2.CloudNode. For sake of example, the topic /camera/image_raw will be used. Identify all topics that need to be compressed. Sudo apt-get install libavdevice-dev libavformat-dev libavcodec-dev libavutil-dev libswscale-dev libx264-dev Install dependencies using the following command Place only the subdirectories ros2_h264_encoder and h264_image_transport in the ROS 2 workspace. Since the H.264 image transport is not a publicly available ROS package, the repositories necessary will have to be manually downloaded.ĭownload the repository linked here using the command git clone -b main -recurse-submodules. PNG/JPEG/Theora Setupĭownload the image_transport_plugins package by running sudo apt-get install ros-image-transport-plugins, where should be replaced by the ROS distribution installed. Note that the encoding/decoding computational power increases from JPEG, Theora, to H.264, but the compression efficiency also increases in that order. If the computer vision algorithm used in the cloud is not robust to the the lossy output of H.264, JPEG, Theora, then it is recommended to use PNG compression. Note that out of the options listed above only PNG is lossless. H.264 decoding is provided through another community package. In particular, JPEG/PNG compression and the Theora compression format are supported through the image_transport_plugins, and FogROS 2 adds additional support for H.264 encoding in ROS 2. FogROS 2 is able to utilize image_transport to set up encoder and decoder nodes that compress and decompress the raw images. Due to the large size of an uncompressed image, there may be adverse effects to round trip time or frames per second when streaming video in a bandwidth constrained environment. One consideration that may pop up when utilizing the cloud for computation is streaming video or images for computer vision.
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