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diff --git a/docs/waltham/1-waltham-client-and-receiver.md b/docs/waltham/1-waltham-client-and-receiver.md deleted file mode 100644 index 061caf9..0000000 --- a/docs/waltham/1-waltham-client-and-receiver.md +++ /dev/null @@ -1,117 +0,0 @@ ---- -title: AGL - waltham client and receiver -author: Naoko Tanibata (Advanced Driver Information Technology) -date: 2019-12-18 - -categories: architecture -tags: architecture, graphics, wayland, Weston, waltham -layout: techdoc - ---- - -**Table of Content** - -1. TOC -{:toc} - -## waltham-client-server-applications - - - -### waltham-client -waltham-client uses Waltham IPC library to connect to remote and transmit client buffers using GStreamer framework. It is designed for AGL upon certain Linux base system with wayland backend. - -waltham-client is divided into two components: - -* waltham-transmitter plugin: - waltham-transmitter plugin provides API to create remote connections and push surfaces over the network and handles both remote output and remote input. - -* waltham-renderer: - waltham-renderer is the implementation for sharing surface. It creates a buffer to be transmitted to other domain. Latest implementation uses GStreamer framework. - -### waltham-receiver - -waltham-receiver is a sample implementation of receiver app which shall be running at remote side. It is developed based on [waltham server](https://github.com/waltham/waltham/tree/master/tests), using Waltham protocol to obtain and process remote output which is sent by waltham-transmitter. -This component is designed to be used for evaluating the functionalities of waltham-transmitter plugin. - -## How it works - -1. Loading and initialization - -The system launches Weston, then Weston loads waltham-transmitter plugin. waltham-client connects to receiver app at remote side during initialization. - - - -2. Establishing connection - -At transmitter_create_remote(), waltham-transmitter creates "struct weston_transmitter_remote" which expresses the receiver object at remote side. Therefore this structure is created for each receiver. -waltham-transmitter sends wth_display_get_registry() and wth_display_sync message() to the receiver app as same manner as Wayland protocol. So that receiver app sends back the resource list to waltham-transmitter. - - - -3. Forwarding surface - -During Weston redraws surface as waltham-transmitter output, waltham-transmitter sends waltham protocol messages to receiver app to notify surface update. wthp_surface_attach(), wthp_surface_damage() and wthp_surface_commit() which correspond to wl_surface_attach(), wl_surface_damage() and wl_surface_commit() message in wayland protocol. -wthp_surface_attach() - Send wthp_buffer as a buffer handling. This is not the actual buffer which contains the data to be rendered but the handle of actual buffer. It abstracts the differences of buffer type. -wthp_surface_damage() - Tell the updated region to receiver app. -wthp_surface_commit() - Tell surface gets updated to receiver app. - - - -4. Rendering using GStreamer - - - -5. Input handling - -For handling input events, waltham-transmitter has 2 ways to secure seat. - 1. Usse wl_seat as weston has. - 2. Create new wl_seat. -Second case is applicable in case transmitter side doesn’t have input device but receiver at remote side has. After wl_seat is created, waltham-transmitter sends input events to weston client application when it gets input event from receiver via waltham protocol. -The message wthp_send_XXX shows you that input event is forwarded from receiver to transmitter, XXX is filled by input event name. - - - -6. Retry connection - -In case the connection gets disconnected during surface sharing, waltham-transmitter shall re-establish the connection. The object “struct waltham_display” represents the connection between the transmitter and receiver, which structure has the flag used to detect disconnection named “running”. In function “connection_handle_data()”, running is set to "false" in case disconnection detected. This flag is checked at every “transmitter_surface_gather_state". When running is false state, waltham-transmitter starts retry handling sequence. First of all, It release the waltham protocol objects then goes to Establish connection sequence mentioned in "2. Establishing connection". - - - -## Waltham in practice -Here is the example how waltham can be used in hypervisor use case of real project . -* Weston is used as the wayland compositor. -* waltham-client is implemented for Weston which acts as a Waltham virtual display. -* Application surface is assigned to Waltham virtual display and it's sent to the other ECU/OS. - Buffers of surface are transferred via GStreamer(UDP), since transferring raw pixel data via Waltham(TCP) is not enough fast. -* Controlling input events (pointer, keyboard, touch) for the surface is handled by Waltham. - - -## How Waltham can be integrated -Here are possible integration examples of waltham. - -### As EGL backend (theoretical possibility) - -Similar to Wayland backend for EGL, Waltham client could be backend in compositer. / -For good performance, a generic surface sharing mechanism is needed in hypervisor environment. -Applications need to adapt to Waltham. Waltham is not designed with this use in mind. This usage is just a theoretical possibility. - - - -### As GStreamer sink (theoretical possibility) - -Similar to Wayland sink, Waltham sink GStreamer plugin can be implemented which sends the buffers to receiver on another domain/OS. -Waltham sink can utilize frame sync and presentation feedback protocols for video synchronization. -For good performance, a generic surface sharing mechanism is needed in hypervisor environment. -Waltham is not designed with this use in mind. This usage is just a theoretical possibility. - - - -### As virtual display in compositor - -Virtual display plugin can be implemented in compositor. This plugin sends client buffers to waltham-receiver in another domain. -No changes to applications. -For good performance, a generic surface sharing mechanism is needed in hypervisor environment. -This is the intended use in mind during design. - - |