Video over DSL with LDGM Codes for Interactive Applications

Digital Subscriber Line (DSL) network access is subject to error bursts, which, for interactive video, can introduce unacceptable latencies if video packets need to be re-sent. If the video packets are protected against errors with Forward Error Correction (FEC), calculation of the application-layer channel codes themselves may also introduce additional latency. This paper proposes Low-Density Generator Matrix (LDGM) codes rather than other popular codes because they are more suitable for interactive video streaming, not only for their computational simplicity but also for their licensing advantage. The paper demonstrates that a reduction of up to 4 dB in video distortion is achievable with LDGM Application Layer (AL) FEC. In addition, an extension to the LDGM scheme is demonstrated, which works by rearranging the columns of the parity check matrix so as to make it even more resilient to burst errors. Telemedicine and video conferencing are typical target applications

Effective AL-FEC with LDGM for interactive video over DSL

Interactive video, due to the need to maintain synchronization, has strict latency requirements. Video streaming to residential users is also constrained by the error bursts that are a feature of Digital Subscriber Link (DSL) access. This paper examines the video response to unlicensed Low-Density Generator Matrix (LDGM) channel codes that combine reduced computational latency and small block sizes with reasonable recovery properties. The paper demonstrates that up to 4 dB gain in video quality is achievable with LDGM Forward Error Correction (FEC) at the Application Layer (AL)