High Quality Video Delivery Over LAN

LectureLink High Quality Video Delivery Over LAN 1. Introduction 2. The Structure of the LectureLink 3. Problems & Solutions 4. Conclusion

1. Introduction 1.1 Distance education in Massey A large cohort of extramural students Paper-based study guidesPaper-based study guides Little contact with the lecturersLittle contact with the lecturers Multi-campus University Papers to be delivered simultaneously to all campuses economies of scalePapers to be delivered simultaneously to all campuses economies of scale

1.2 LectureLink — Solution of the distance education 1.2 LectureLink — Solution of the distance education What is LectureLink? An audio-visual application which enable people to communicate over network synchronously Network

1.2.2 What features does it have? What features does it have? High qualityHigh quality — MPEG1: 352 * 288 resolution with 25 frames/s — MPEG2: 720 * 576 resolution with 50 frames/s — Full TV resolution

Snapshots in different encode quality Snapshots in different encode quality MPEG1 codec with throughput of 1.5 Mbps MPEG1 codec with throughput of 1.5 Mbps MPEG1 codec with throughput of 0.8 Mbps MPEG1 codec with throughput of 0.8 Mbps

High speed High speed — Throughput 0.4 – 10.0 Mb/s — Transfer latency around 1 s

High stability High stability — Average data loss Control signal: one-way 0 % two-way 0 % Audio-visual signal: one-way 1 % two-way 3 % — Automatic resume after network cable broken and reconnected

1.2.3 How does it work? How does it work? Audio-visual codecs:Audio-visual codecs: — Wired MPEG1 / MPEG2 codec cards up to 100:1 compress ratio — QuickTime software decode: cheap solution (coming soon)

Network streaming strategy Network streaming strategy — Small MPEG packages with complete encode info. — Optimized memory buffers for fast and stable transfer

IP based transferring protocol IP based transferring protocol — TCP for control channels transmission — UDP for A-V channels transmission

Ethernet / ATM physical network layer Ethernet / ATM physical network layer — Ethernet: Up to 10 Mbits/s throughput — ATM: Up to 100 Mbits/s throughput

2. The Structure of the LectureLink 2.1 Application requirement Hardware: PowerPC 200 MHz CPU or higherPowerPC 200 MHz CPU or higher 32 MB built-in memory (64 MB recommended)32 MB built-in memory (64 MB recommended) Butane II MPEG2 encoding cardButane II MPEG2 encoding card Mason X MPEG decoding cardMason X MPEG decoding card Color video camera with resolution 300 lines or higherColor video camera with resolution 300 lines or higher Color TV monitor with A-V inputColor TV monitor with A-V input

Software: Software: Mac OS 8.5 or laterMac OS 8.5 or later QuickTime 3 or laterQuickTime 3 or later A permanent IP addressA permanent IP address

2.2 The LectureLink application structure Work sequence Work sequence

System component System component

3. Problems & Solutions 3.1 Problems –Data loss –Transfer latency

3.2 Solutions 3.2 Solutions Data transfer analysis Frequency comparison in two-way transfer Frequency comparison in two-way transfer

3.2.2 Data Loss Data Loss Transfer bandwidth and encoding bit rateTransfer bandwidth and encoding bit rate Figure 4 Data lost in different encoding bit rate during transfer

Influenced by the encoded data buffer size Influenced by the encoded data buffer size Figure 2 Three lists of encoded data buffers Video Buffers Video Audio Encode card Network Encode card Audio buffers Multiplex Buffers

Optimized buffer sizes Optimized buffer sizes The buffer sizes in different encoding bit rate (Optimised) The buffer sizes in different encoding bit rate (Optimised) Encode bit rateVideo buffersMultiplex buffers Total (Mbps) Video (Kbps)Total size (Mbits) Buffer size (Kbits) Number of buffers Total size (Kbits) Number of buffers

3.2.3 Transfer Latency Transfer Latency Three type of transfer latencies Three type of transfer latencies Sending waiting delay Encode card Decoding waiting delay Other delay Decode card Other delay Network

Time delay for different encode bit rate in two-way transfer Time delay for different encode bit rate in two-way transfer

4. Conclusion LectureLink has little data loss LectureLink has little data loss LectureLink has acceptable data transfer latency LectureLink has acceptable data transfer latency Use optimal buffer size to initialize data buffers Use optimal buffer size to initialize data buffers Decode waiting delay is the main target for the further latency improvement Decode waiting delay is the main target for the further latency improvement Bandwidth expansion will be the main point for the future development Bandwidth expansion will be the main point for the future development