Your SlideShare is downloading. ×
0
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Requirements for the Transmission of Streaming Video in ...
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Requirements for the Transmission of Streaming Video in ...

822

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
822
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
13
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide
  • This is initial work on the subject – focusing on wireless network characteristics No specific work on Visual Attention, BUT setting the limits over which video transmission does not provide meaningful visual reference.
  • Objective methods aim at determining the quality of a multimedia sequence in the absence of the human viewer. A classification based on the existence of the original multimedia stream distinguishes three approaches: full reference methods (based on picture comparison), reduced reference solutions (relies on feature extraction) and no reference methods (also called single-ended). Only the last category of methods is useful for in- service applications and are used during streaming when the original clip is not available and have strict timing requirements. The first two approaches are called out-of service methods and are used offline when the original sequence is fully available and no time constraints are imposed. Most of these methods have associated metrics in order to allow for quantification of the end-user perceived quality .
  • The PSNR is measured in dB (higher value corresponds to better quality). SAMVIQ is based on random playout of the test files. The individual viewer can start and stop the evaluation process as he wishes and is allowed to determine his own pace for performing grading, modifying grades, repeating playout when needed, Through this study we tried to correlate PSNR and MOS and provide some useful results. For this purpose we conducted some simulations using this evaluation setup (new slide) and scenarios.
  • Adopting the transmission of compressed MPEG-4 video we will investigate in detail the results when playing the stream at the receiver while we have faults in the transmission of parts of the stream.
  • To identify if and how the different parameters affect the objective value of PSNR we compare them in pairs. Objective values remain relatively constant with the change in either variable with a slight general increase for high link BW values. Overall upward shift by 1dB when the encoding rate is increased. Very low PSNR whenever encoding rate is higher than the link BW (right figure).
  • For 1Mbps case the results are similar to the previous ones. For the 500Kbps case we observe that the PSNR remains at the same levels with respect to delay, but is significantly reduced when the video encoding rate is at 500Kbps and 768Kbps (~15dB). Stronger relationship between link BW and encoding rate than between the link BW and the propagation delay.
  • For both values of delay considered the PSNR drops dramatically when the encoding rate is higher than the link BW.
  • The set of video streams that were recorded on the receiving site of the evaluation setup was used as input to the PQoS evaluation method explained in Section 3.2. We used the software tool called "MSU Perceptual Video Quality tool" which is a tool for subjective video quality evaluation implementing SAMVIQ. The score grades in this method range from 0 to 100. The videos were evaluated by a group of 20 students at the University of Cyprus. Table 3 presents the relationship between the average value of the students' subjective grading and the objective value obtained through EvalVid. It is clear from the table that the range of PSNR values corresponding to each category is not similar and do not have a liner relationship with the MOS. The video streams which scored high had also an extremely high PSNR. The Good and Fair categories have also a small range of PSNR values (0.3dB and 0.8dB respectively) whereas the low categories get the bulk of the scores. This phenomenon illustrates clearly how inappropriate is PSNR to evaluate the actual QoS as perceived by the user.
  • The higher the percentage of lost frames the lower the PSNR values and hence the video objective quality
  • Transcript

    • 1. Requirements for the Transmission of Streaming Video in Mobile Wireless Networks Vasos Vassiliou, Pavlos Antoniou, Iraklis Giannakou, and Andreas Pitsillides Net works R esearch L ab (NetRL) C omputer S cience D epartment U niversity of C yprus
    • 2. Scope of the presentation <ul><li>Present the characteristics of mobile wireless networks. </li></ul><ul><li>Relate these characteristics to the requirements for video transmission. </li></ul><ul><li>Establish guidelines for the transmission of video, based on the limits of mobile and wireless networks as well as on objective and subjective (perceptual) measurements. </li></ul>
    • 3. Research Goals <ul><li>Investigate the types of errors that can be observed, using objective video quality metrics such as PSNR by adopting the transmission of MPEG4-encoded video streams over wireless network environments. </li></ul><ul><li>Provide subjective video quality estimation based on the evaluation of decoded video streams by informed viewers. </li></ul><ul><li>Provide high quality transmission of video streaming based on </li></ul><ul><ul><li>objective QoS metrics measured in the network, </li></ul></ul><ul><ul><li>subjective quality measures obtained by video viewers at end hosts. </li></ul></ul>
    • 4. Characteristics of Mobile Wireless Networks <ul><li>Cellular Wireless Networks </li></ul><ul><li>2G – GSM: Very stable, widely accepted but does not support high data rate (only up to 9.6Kbps). </li></ul><ul><li>2.5G – GPRS: Designed to provide a high data rate packet-switched service in a GSM network (up to 384Kbps). Provides important benefits with respect to data and video. </li></ul><ul><li>3G – UMTS: Provides global mobility with wide range of services. Different QoS classes for 4 types traffic (up to 2Mbps). </li></ul>
    • 5. Characteristics of Mobile Wireless Networks (ctd.) <ul><li>WLAN – IEEE 802.11 (WiFi - CSMA/CA) </li></ul><ul><li>a) Operates on the 2.4GHz band with maximum theoretical data rate of 54Mbps. </li></ul><ul><li>b) Based on common resource sharing MAC protocol which does not guarantee any QoS. </li></ul><ul><li>c) Data rate allocated to each user is inversely proportional to the number of users in the local network. </li></ul>
    • 6. Characteristics of Mobile Wireless Networks (ctd.) <ul><li>WiFi (WLAN) offers higher data rates (up to 54Mbps) within a single Access Point range. No handoff support. </li></ul><ul><li>UMTS (3G) and GPRS (2.5G) provide service continuity and seamless mobility due to handoff mechanism but they both operate in lower data rates (especially GPRS). </li></ul>
    • 7. Video Quality Assessment Schemes <ul><li>Objective QoS measures </li></ul><ul><li>Classified in 3 categories based on the existence of the original stream: </li></ul><ul><ul><li>The original video sequence is compared to the decoded video sequence ( Full Reference ) i.e. PSNR, </li></ul></ul><ul><ul><li>The original video sequence and the impaired one are fed to a computer algorithm that calculates the distortion between the two ( Reduced Reference ), </li></ul></ul><ul><ul><li>Observations are made only on decoded video and estimation of the quality is done using only that information ( No Reference ). </li></ul></ul>
    • 8. Video Quality Assessment Schemes (ctd.) <ul><li>Subjective QoS measures </li></ul><ul><li>Perceived measure of the quality of a video is done through the human &quot;grading&quot; of streams which helps collect and utilize the general user view (Mean Opinion Score - MOS). </li></ul><ul><li>Subjective measures are extracted from marks given by people, and can help to evaluate users' opinion. </li></ul>
    • 9. Video Quality Assessment Schemes (ctd.) <ul><li>Objective QoS metric: PSNR (Full Reference Method) – Measured in dB. </li></ul><ul><li>Subjective QoS metric: SAMVIQ (Subjective Assessment Method for Video Quality evaluation) </li></ul><ul><ul><li>a) Submitted as draft standard to ITU-R SG6 WP 6Q, </li></ul></ul><ul><ul><li>b) Uses a continuous scale graded from 0 to 100 annotated by 5 quality items linearly arranged </li></ul></ul><ul><ul><li>(Excellent, Good, Fair, Poor, Bad), </li></ul></ul><ul><ul><li>c) Based on random playout of the test files. </li></ul></ul><ul><ul><li>The individual viewer can start and stop the evaluation process as he wishes and is allowed to determine his own pace for performing grading, modifying grades, repeating playout when needed. </li></ul></ul>
    • 10. Evaluation Setup & Scenarios <ul><li>We used NS2 simulation package and video streams of different content and characteristics so that the influence of errors in the wireless network is visible at the video stream reconstructed at the receiver. </li></ul><ul><li>Simulation test-bed </li></ul>
    • 11. Evaluation Setup & Scenarios (ctd.) <ul><li>Variable Network Test Parameters </li></ul><ul><li>Test Sequences </li></ul>
    • 12. Results Variable Link Bandwidth and Propagation Delay <ul><li> 64Kbps encoding rate 256Kbps encoding rate </li></ul><ul><li>Higher encoding rate increases PSNR </li></ul>
    • 13. Results (ctd.) <ul><li>Variable Video Encoding Rate and Propagation Delay </li></ul><ul><li> 500Kbps link bandwidth 1Mbps link bandwidth </li></ul><ul><li>Stronger relationship between link BW and encoding rate than between the link BW and the propagation delay. </li></ul><ul><li>Propagation delay does not affect PSNR </li></ul>
    • 14. Results (ctd.) <ul><li>Variable Link Bandwidth and Video Encoding Rate </li></ul><ul><li> 10ms delay 400ms delay </li></ul><ul><li>PSNR LOW if Encoding rate > Link BW </li></ul>
    • 15. Perceived QoS Evaluations <ul><li>Relationship between PSNR and MOS </li></ul><ul><li>PSNR does not have linear relationship with the MOS. </li></ul><ul><li>PSNR is inappropriate for the evaluation of the actual user perceived quality of service (poorly correlated to human vision). </li></ul>
    • 16. Conclusions <ul><li>Objective video quality - as this is reflected through PSNR values - depends on the percentage of lost frames. </li></ul><ul><li>End-to-end delay does not play an essential role in the objective video quality but it remains a critical factor for real-time services and may influence the subjective video quality. </li></ul><ul><li>Results show that the higher the video encoding bit rate the higher the QoS in terms of objective and subjective video quality measures. </li></ul><ul><li>Results show the inappropriateness of PSNR for the evaluation of the actual user-perceived QoS. </li></ul>
    • 17. <ul><li>THE END </li></ul><ul><li>THANK YOU VERY MUCH </li></ul>

    ×