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Video Quality Research @ IBCN. Video Quality Research @ IBCN. Real-time Video Quality Monitoring/Testing Monitor Probe Virtual Wall Video Quality Metrics Full Length Movie Quality Assessment Visual Quality Impairment Detector VQEG involvement Video Streaming xStreamer. - PowerPoint PPT Presentation
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Video Quality Research @ IBCN
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Video Quality Research @ IBCN
Real-time Video Quality Monitoring/Testing Monitor Probe Virtual Wall
Video Quality Metrics Full Length Movie Quality Assessment Visual Quality Impairment Detector
VQEG involvement Video Streaming
xStreamer
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Real-time Video Quality Monitoring/Testing
Monitor probe Real-time monitoring of H.264/AVC streams at several
demarcation points Gather both network statistics and video statistics
Packet loss, delay, jitter Macroblock & motion vector information
N. Vercammen, N. Staelens, B. Vermeulen and P. Demeester, “Distributed Video Quality Monitoring”, to appear in Proceedings of 2nd IEEE International Workshop on Internet and Distributed Computing Systems (IDCS'09), December 10-12, Korea
Monitor probe
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Real-time Video Quality Monitoring/Testing
Virtual Wall & Video testbed Video testbed
Automate video quality tests Virtual wall
Enables creation of multiple video testbeds N. Vercammen, N. Staelens, B. Vermeulen and P.
Demeester, “Extensive video quality evaluation: A scalable video testing platform”, Proceedings of 1st IEEE International Workshop on Internet and Distributed Computing Systems
Scalable Video Testing Platform
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Video Quality Metrics
Full Length Movie Quality Assessment Existing video quality assessment methodologies:
Evaluate short video sequences (~ 15s) Users are actively evaluating visual quality Overall test duration limited to 30 minutes
Watching television At home, living room, with family (social viewing) Longer content: movies, television programs Lean backward TV viewing experience
=> how is quality perceived while watching full length movies, when users are not focused on quality evaluation
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Full Length Movie Quality Assessment
Error Visibility Frame freeze in movie <-> frame freeze in short
sequences: 42% <-> 91% Blockiness in movie and short sequences: both 98%
Error Annoyance Standard test: freezes rated higher quality than
blockiness Movie: frame freezes are more annoying
Conclusion Focus is important Flow experience
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Full Length Movie Quality Assessment
N. Staelens, B. Vermeulen, S. Moens, J.-F. Macq, P. Lambert, R. Van de Walle and P. Demeester, “Assessing the influence of packet loss and frame freezes on the perceptual quality of full length movies”, Proceedings of Fourth International Workshop on Video Processing and Quality Metrics for Consumer Electronics (VPQM-09)
N. Staelens, S. Moens, W. Van den Broeck, I. Mariën, B. Vermeulen, P. Lambert, R. Van de Walle and P. Demeester, “Assessing the perceptual influence of H.264/SVC signal-to-noise ratio and temporal scalability on full length movies”, Proceedings of First International Workshop on Quality of Multimedia Experience (QoMEX 2009)
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Video Quality Metrics
Visual Quality Impairment Detector Current research focus Real-time visual impairment detection
Network level => detect losses Video level => determine severity and visibility
Target No-Reference metric or Reduced-Reference Will be implemented in the monitor probe
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VQEG involvement
Ghent University – IBBT involved in VQEG Meeting hosted, September 22 – 26, 2008
Contributes to MM testplan (already finalized)
ITU-T J.246 & ITU-T J.247 Hybrid testplan:
co-editors HDTV testplan
Independent Lab Group (ILG) Joint Effort Group (JEG)
Toolchain for creating impaired sequences H.264/AVC parser, based on JM reference software
xStreamerModular Multimedia Streaming
xStreamer
In-house developed modular multimedia streamer Alexis Rombaut ([email protected])
Written in C++ Uses libraries:
libavformat/libavcodec (parsing/encoding/decoding)
live555 (RTSP)
jrtplib (RTP)
Released under General Public License (GPL) Freely available at http://xstreamer.atlantis.ugent.be/
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Modular Multimedia Streaming
Inspired by Click Modular Router & DirectShow
Offers different components Performs basic functions Readers, packetizers, multiplexers, schedulers,
transmitters, receivers, writers, classifiers, analyzers
Streamer is directed graph of components
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Modular Multimedia Streaming
Supports audio and video
Using RTP packetization: MPEG-1/2/4 Video & Audio
Using MPEG-2 Transport Streams: MPEG-1/2/4 Video & Audio H.264 AVC/SVC
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Modular Multimedia Streaming
Multitude of supported protocols
RTP/UDP
RTSP/RTP/UDP
UDP
TCP
What can xStreamer do?
Advanced streaming server Own MPEG-2 TS multiplexer SVC streaming Differentiated streaming using classifiers
Proxy/client Proxy: convert differentiated stream into
a single stream Client: save captured stream to file
Video tool No ‘real’ streaming involved Simulate packet loss Collect tracefiles during streaming
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Create xStreamer configuration
Configuration saved in XML-based file Describes directed graph of components and
connections between components
Graphical User Interface Visualize directed graph Drag components and draw connections Configure components
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Example: Differentiated SVC streaming
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Read raw H.264 video
stream
Packetize frames into packets as
defined in RFC3984
Avoid bursts by smoothing packets
over time
Classify NAL units depending
on SVC layer
Stream different layers over different
connections
Example: Proxy/Client
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Proxy Client
xStreamer as video tool
Offline simulator No ‘real’ streaming Simulate packet loss using Classifier component
Random, Gilbert-Elliott Write resulting packet stream back to file
Tracefile generation Packetizer: video trace Transmitter: sender trace Receiver: receiver trace Classifier: sender & receiver trace
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Publication
‘xStreamer: Modular Multimedia Streamer’ accepted for publication on ACM Multimedia 2009 - Open Source Software Competition, Beijing, ChinaOctober 19-24, 2009
Distributed transcoding with xStreamer
Current: Architecture
Transcoder
1
Transcoder
1
ProxyProxyTranscoder
…
Transcoder
…
Transcoder
N
Transcoder
N
ServerServer
Input
File
Input
File
Output
File
Output
File
Current: Server
DifferentiatorDifferentiatorffmpeg-
reader
ffmpeg-
reader
RTP
transmitter 1
RTP
transmitter 1
RTP
transmitter …
RTP
transmitter …
RTP
transmitter N
RTP
transmitter N
Send each new GOP to the next transcoder
= RR (round robin) distribution
note: the schemes omit some components for clarity
Current: Transcoder
xstreamer
unpacketizer
xstreamer
unpacketizerRTP
receiver
RTP
receiver
transcodertranscoder
xstreamer
packetizer
xstreamer
packetizerRTP
transmitter
RTP
transmitter
Current: Proxy
ffmpeg-
writer
ffmpeg-
writermultiplexermultiplexer
RTP
receiver 1
RTP
receiver 1
RTP
receiver …
RTP
receiver …
RTP
receiver N
RTP
receiver N
First experimental results
The following slides show the results from the first experiments on the virtual wall.
Experiment parameters: All sequences are 90 minutes long, encoded with H.264 at 25
frames per second.
Future work will experiment with different bit rates for each resolution.
Sequence Resolution Bitrate (kbps)
QCIF 176x144 100
CIF 352x288 400
4CIF 704x576 1600
720p 1280x720 3600
1080p 1920x1080 8100
Scalability
The figure shows the how much faster than real-time (factor) we can transcode in function of the number of nodes.
For example, using 20 nodes the system can transcode from 1080p to QCIF 100 times faster than real-time, transcoding 90 minutes of video in less than 1 minute.
Some curves flatten because the server cannot stream more than 1 Gbps to feed the transcoding notes, future work will alleviate this by using several network interfaces.
Codec comparison
Provides the same information as the previous figure but organized in function of the source resolution.
As target resolutions become larger the influence of the source resolution decreases (encoding, determined by target resolution, consumes more resources than decoding, determined by source resolution).
For example transcoding 1080p to 4CIF is not much slower than transcoding 720p to 4CIF (blue bars).
Transcoding duration
The figure shows the considerable processing power by transcoding 90 minutes of video in mere 10 seconds for the smallest resolutions.
For the highest resolutions, the system can transcode 90 minutes of video from 1080p to 720p in less than 4 minutes.
The times to transcode 1080p to QCIF and 1080p to CIF are same because the server could not feed the former adequately.
Conclusion
The first experiments show promising results by transcoding between 25 and 500 faster than real-time depending on the resolutions using 32 nodes.
Some combinations did not fully scale up to 32 nodes because the server bit rate would exceed 1 Gbps. However, future work, using multiple interfaces or multiple servers will avoid this.
Future experiments will increase the number of nodes up to 100.