1. ISWN (Integrated Services Wireless Network) Richard Akester UCL

2. Introduction Test network –Software DVB-T –Stream Types –Multiplexes 802.11 –Infrastructure/Ad-hoc –Unicast/Multicast Network Support Future Work

3. Test network DVB-T ADSL 802.11b

4. Software tzap ts2ps tuner kernelApp space demux TV SERVERCLIENT App spacekernel udprecv mplayer ALSA X11 Multicast Over 802.11

5. Elementary Stream (ES) Video (MPEG2): IBBPBBPBBPBBPI I: Intra frames, P: Predictive frames, B: Bi-directional frames GOP: 12, (~2 GOPs/sec@25fps [PAL]), 4-6Mbps Audio (MP2): AAAAAAAA A: Audio frames (1152 audio samples [24ms@48kHz, ~42fps]) 128-256kbps

6. Packetized Elementary Stream (PES) 00 Header: 0001PT PT (Payload Type): 0xE0=1 st video stream, 0xC0=1 st audio stream Length: usually 2048 (2K) bytes (but can be less) LengthFlag1Flag2hlengthpts

7. Transport Stream (TS) Header: 0x47FlagsPIDFlags Adaptation Field Header+Body = 188 bytes PID (Program ID): allows programs to be multiplexed, but also distinguishes between substreams [eg BBC1 PIDs: 600 (video), 601 (audio), 603 (subtitles), 4167 (teletext)] Special PIDs: NIT (Network Information Table), SDT (Service Description Table), PMT (Program Map Tables), PAT (Program Association Table).

8. DVB-T Multiplexes 1 (18Mbps): BBC 1, BBC 2, BBC 3, BBC News 24, CBBC 2 (24Mbps): ITV 1, ITV 2, Channel 4, Teletext, ITV News, FourText, Ch 14 A (24Mbps): five, TV Travel Shop, QVC, bid-up.tv, ntl, Ch 15, BBC Radio 1, 2, 3, 4 B (18Mbps): BBC 4, CBeebies, BBC Parliament, 1Xtra, BBC R5 Live, BBC 5L SportsX, BBC 6 Music, BBC 7, BBC Asian Net, Community, 701, 702, 703 C (18Mbps): UK History, Sky News, Sky Travel, Sky Sports News, Magic, Hits Radio D (18Mbps): The HITS, TMF, f tn, UKBrightIdeas, CBM, Free2Play, Q, Magic, Hits Radio, BBC World Sv, oneword, jazz fm, Kerrang!, Smash Hits!, Kiss

9. 802.11 ad-hoc network Consumer electronic devices may use this mode (no access point) No option to use PCF (have to use DCF) –Although IEEE802.11e… Distributed beaconing

10. Unicast sender receiver RTS (Request To Send) CTS (Clear To Send) DATA ACK

11. Multicast sender receiver DATA

12. RTP (Realtime Transport Protocol) RFC2250 (how to carry MPEG2 video and audio in RTP) –A) encapsulate PS/TS in RTP headers Often done (eg dvbstream) –B) encapsulate ES in RTP headers with extra header info added Not so common…

13. Streaming software Dvbstream –Designed for dvb-s (satellite) but could be rewritten for dvb-t –Sends TS/PS encapsulated in RTP ffmpeg/ffserver –ffmpeg can transcode MPEG2->MPEG4 –ffserver can serve resulting “file” over HTTP VideoLAN –Vlc: client/player that can also transcode/act as a server

14. Future Work Partial transcoding (http://www.ecse.rpi.edu/CNGV/publications/199 8_PR/iab_talk_jw.pdf) Subtitles/EPG incorporating into OSD Channel zapper: web interface? PVR –Programmable by web interface –Time/Date/Channel OR just click on program name!