pydvbcss is a library implementing DVB "CSS" protocols for Companion Screen Synchronisation.
- `How to install <#install-the-code>`__
- `Read the documentation <#read-the-documentation>`__
- `Run the examples <#run-the-examples>`__
pydvbcss is a set of Python 2.7 libraries and command-line tools that implement some of the protocols defined in the DVB CSS specification (published as ETSI 103-286 part 2) and are used for the “inter-device synchronisation” feature in `HbbTV 2 <http://hbbtv.org/resource-library/>`__. These protocols enable synchronisation of media presentation between a TV and Companion devices (mobiles, tablets, etc).
This library includes simple to use high level abstractions that wrap up the server or client behaviour for each protocol as well as low level code for packing and unpacking messages sent across the protocols. There are also objects that work with the rest of the library to represent clocks and timelines.
This code is intended as an informal reference and is suitable for building prototypes and testing tools that implement TV (server) or Companion (client) behaviour. It is not considered production ready or suitable for integration into consumer products.
The code does not implement media playback functionality and this is not a planned feature.
pydvbcss has been developed on Mac OS X 10.10 but has also been used successfully on Microsoft Windows 7 and Ubuntu 14.04.
Read the Documentation
The docs for the library can be read online on readthedocs.org:
Links are also available from those pages through to documentation for earlier releases.
Install the code …
On Mac OS X and Linux you may need to run one or more of the commands as root.
Using PyPi (core library only, no examples or tools)
If you ONLY want the library (not the code examples and tools ) and if you don’t require the very latest bugfixes, then you can install a recent release package from the Python Package Index (PyPI) using pip:
$ pip install pydvbcss
Or if upgrading from a previous version:
$ pip install --upgrade pydvbcss
You can use pip search pydvbcss to verify which version is installed.
From Github or a release tarball (includes examples and tools)
The master branch is the latest state of the code, including any recent bugfixes. It is mostly stable but might have occasional small API changes. Release snapshots are also available but won’t contain the very latest bugfixes or new features. Both of these options include the full code, including examples.
First you need to install dependencies…
$ pip install 'cherrypy' $ pip install 'ws4py'
Then take (or update) your clone of the repository master branch, or download and unzip a snapshot release and run the setup.py script to install:
$ python setup.py install
This will install all module packages under ‘dvbcss’.
There is a limited test suite (it only tests certain classes at the moment). Run it via setup.py:
$ python setup.py test
This checks some timing sensitive implementation issues, so ensure you are not running any CPU intensive tasks at the time.
Running the examples and tools
There is a set of example and tools demonstrating simple servers and clients for the protocols included with the library. See the quick start guide in the documentation to see how to run them.
The clients are useful tools to test a TV implementation is outputting the correect data.
The servers can be modified to simulate a TV that is playing content with an ID and timeline(s) that a companion application expects.
Example: checking protocols implemented by a TV
Start the content playing on the TV and ensure it is serving the protocols (for HbbTV 2 TVs this requires an HbbTV application to enable inter-device synchronisation).
Suppose the TV is serving the CII protocol at the URL ws://192.168.0.57:7681/cii…
To check the CII protocol:
$ python examples/CIIClient.py ws://192.168.0.57:7681/cii
Suppose that the messages returned report the URL of the TS protocol endpoint as being ws://192.168.0.57:7681/ts and the wall clock protocol as being at 192.168.0.57 port 6677…
To check the TV’s Wall Clock protocol:`
$ python examples/WallClockClient.py 192.168.0.57 6677
To check the TV reporting a PTS timeline (uses both Wall Clock and TS protocols):
$ python examples/TSClient.py ws://192.168.0.57:7681/ts \ udp://192.168.0.57:6677 \ "" \ "urn:dvb:css:timeline:pts" \ 9000
Super-quick introduction to the protocols
DVB has defined 3 protocols for communicating between a companion and TV in order to create synchronised second screen / dual screen / companion experiences (choose whatever term you prefer!) that are implemented here:
- CSS-CII - A WebSockets+JSON protocol that conveys state from the TV, such as the ID of the content being shown at the time. It also carries the URLs to connect to the other two protocols.
- CSS-WC - A simple UDP protocol (like NTP but simplified) that establishes a common shared clock (a “wall clock”) between the TV and companion, compensating for network delays.
- CSS-TS - Another WebSockets+JSON protocol that communicates timestamps from TV to Companion that describe the current timeline position.
The TV implements servers for all 3 protocols. The Companion implements clients.
There are other protocols defined in the specification (CSS-TE and CSS-MRS) that are not currently implemented by this library.
Building the documentation for yourself
You can also build the documentation yourself. It is written using the sphinx documentation build system.
Building the documentation requires sphinx and the sphinx “read the docs” theme. The easiest way is using PyPI:
$ pip install sphinx $ pip install sphinx_rtd_theme
The docs directory contains the configuration and main documentation sources that descibe the structure. Most of the actual words are in the inline docstrings in the source code. These structural pages pull these in.
To build docs in HTML format, either:
$ python setup.py build_sphinx
$ cd docs $ make html
Contact and discuss
Discuss and ask questions on the pydvbcss google group.
The original author is Matt Hammond ‘at’ bbc.co.uk
All code and documentation is licensed under the Apache License v2.0.
If you would like to contribute to this project, see CONTRIBUTING for details.