Wednesday, 02 September 2009
Many of the tools provided on this site are offered for free or as open source software to help promote innovation and new developments in Mobile Multimedia Broadcasting and the DAB/DMB digital radio technology. However, the free and unrestricted distribution of standardised DAB audio codecs as part of free or open source projects is not possible. These codecs are royalty-based.
To provide a free option for audio applications on DAB, we have integrated a CELT library. CELT is a codec being developed by the Xiph.org foundation. Because it is available on a royalty-free basis, we will be able to distribute our CELT library as part of our mmbTools live CD, our realtime audio encoding platform, our "Openmokast for openmoko" player and our "Openmokast for Android" player.
Interestingly, CELT is designed for low-delay applications and can generate CBR streams. These two features are particularly interesting in the context of live digital radio and DAB where channel capacity is fixed. Consequently, CELT and DAB could prove to be a very good match.
As a first step, we have integrated a "portable" library based on the source code provided by the CELT project. This library compiles on the various platforms that we use for our projects: Ubuntu, Android/G1 and Openmoko/FreeRunner. On Ubuntu, our CELT library is planned to run as a GStreamer plug-in.
Additionally, we designed a simple transport protocol for CELT over DAB. This protocol has been implemented successfully in a functional live system to be demonstrated for the first time at the IBC 2009, Stand 3.D02.
We intend to release our CELT library as open source software and to provide an extensive description of our CELT over DAB transport protocol in the coming weeks.