Title: Sergei N. Kozlov, s.n.kozlov@tue.nl
1Streaming MPEG video over wireless link
- QoS in Digital In-home Networks
- PROGRESS project EES.5653
2Agenda
- I-frame delay (summary on the approach)
- Progress since May 2004
- Future plans
- Demo
3Video over wireless link
- Typical scenario video transmission from a
set-top box to the (mutiple) screens
Between 5 and 13 seconds a microwave oven is on
?t50ms
- Wireless link
- Low and highly variable throughput
4Sender/receiver communication (RTP-based)
video source
video sink
Packets get lost here
sender buffer
receiver buffer
MAC retransmission mechanism
wireless interface (sender)
wireless inerface (receiver)
5MPEG encoding
- GOP (group-of-pictures)
- Frame types I, P, B
- Typical GOP structure and dependences
I BBPBBPBB(I)
6Importance of I and P frames
- Missing of I/P frames causes video artefacts
- A complete stream only missing B frames has
- no artefacts
In worst case you only get 8.3fps from originally
25fps
7Cumulative weight of B-frames
- An example of a 5Mbps stream (LOTR)
- B-frames make up more than 50 of the whole
bitrate
8Link layer approach
Sender
MAC-retransmissions
Application/ encoder
Selectively drop frames here
video stream
IP packets
OS network stack
scheduler buffer
9I-frame delay (IFD)
Stream generated by application
Transmitting under low and variable throughput
some frames take longer time
Frames displayed at receiver NN 1, 4, 5, 8 are
skipped
10Pros and cons of link layer approach
- We only need to modify sending part
- it will work with any terminals supporting RTP
reception and equiped with a general MPEG decoder - due to RTP (UDP-based), it can be used for
broadcasting - It is very reactive against fast network
fluctuations
- Requires access to wireless interface
- should be implemented at every sending device
11Deployment of IFD
- ASL, SC (Ewout Brandsma, Eric Persoon)
- CE Connected Planet project (Tom Suters,
Daniel Meirsman) - SLx00 products (Streamium)
- CES at Las Vegas in June 2005 (with CE)
- CRE in June 2005 (with ASL)
12Progress since May 2004
- A publication submitted to WoWMoM 2005
- A demo set-up created
- a number of successful demonstrations given
- Deployment of IFD into real projects started (SC
CE) - Future work made concrete (coming slides)
- Yesterday IFD proved to work with a Linksys AP
- IFD and wired wireless network
- streaming to wireless CE devices (such as
HotMan-2)
new
13Further work (I) Evaluation of IFD models,
simulations and optimizations
- Simulator (based on ns2)
- variations of network topologies
- variations of algorithms/buffer sizes for IFD
- variations of video stream (GOP pattern
variations, bit-rates, coding standards etc)
Optimal settings are the simulation goal
14Future work (II) IFD above transport layer
- If...
- we dont have direct access to the wireless
interface - we dont want to modify it
- we want to use it with both wired/wireless
networks - we want it over a reliable transport protocol
- ... Then we would like to look at the tranport
layer - implement the same idea in the application layer
above TCP (master-student working on that)
15Future work (III) IFD SNR scalability
(together with Dmitry)
- The goal is to handle even higher variations in
the link bandwidth - KISS project at NatLab is implementing it
16Welcome to the demo!(given after the meeting)