User Guide EXpert IPTV Test Tools
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CONTENTS LICENSE AGREEMENT AND WARRANTY ................................................................................. 3 CHAPTER 1 INTRODUCING THE EXPERT IPTV TEST TOOLS ...................................................10 CONVENTIONS ....................................................................................................................13 CHAPTER 2 SAFETY INFORMATION....................................................................................14 SAFETY INFORMATION ...............
CHAPTER 7 7.1 7.2 7.3 7.4 CHAPTER 8 RUNNING IPTV TESTS ......................................................................................21 SIMULTANEOUS TESTING OF MULTIPLE CHANNELS ...................................................... 21 PASSIVE TEST..................................................................................................... 21 SET TOP BOX EMULATION TEST.............................................................................. 23 ETHERNET INTERFACE STATUS ................
A.1.1.1 A.1.1.2 A.1.1.3 A.1.2 A.1.2.1 A.1.2.2 A.1.2.3 A.1.3 A.1.3.1 A.1.3.2 A.2 A.2.1 A.2.1.1 A.2.1.2 A.2.1.3 A.2.1.4 A.2.1.5 A.2.1.6 A.2.1.7 A.2.2 A.2.3 A.2.3.1 A.2.3.2 A.2.3.3 A.3 A.4 A.5 Impact of Packet Loss and Jitter on Video Quality ............................................47 Impact of Packet Loss on Specific Video Codecs .............................................49 Playout Buffer Configuration ..........................................................................
Chapter 1 Introducing the EXpert IPTV Test Tools The EXpert IPTV Test Tools is a software platform (FTB-1, FTB-2, and FTB-2 Pro) based IPTV quality analyzer.
When used as a passive monitoring device The EXpert IPTV Test Tools is connected via a manageable switch or aggregating tap to monitor bidirectionally the IGMP, RTSP and other protocols, and IPTV streams from the video server. In both connection modes video and audio quality assessment is provided by VQMON algorithm. Test results are continuously accumulated and saved on the platform hard drive. Live test results can be watched on the screen.
Conventions Before using the product described in this guide, you should understand the following conventions: WARNING Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury. Do not proceed unless you understand and meet the required conditions. CAUTION Indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury. Do not proceed unless you understand and meet the required conditions.
Chapter 2 Safety Information Safety Information Laser Safety Warnings WARNING Do not install or terminate fibers while a laser source is active. Never look directly into a live fiber, and ensure that your eyes are protected at all times. Laser Safety Information The EXpert IPTV Test Tools software is not provided with any hardware components. However, it may be used with your platform or modules which may contain laser components.
Chapter 3 Getting Started The EXpert IPTV Test Tools application is preinstalled on the platform. If The EXpert IPTV Test Tools is not installed, refer to the platform User Guide for more information on how to install the application. Starting Application You can access many tools directly from your unit. To start an application: 1. FTB-1: From Mini Toolbox, select the Test Tools tab. FTB-2 and FTB-2 Pro: From ToolBox X, select the Test Tools button. 2. Click on the Expert IPTV Test Tools.
Chapter 4 Physical Interface Ethernet 10/100/1000 Mbits/s Ethernet Port The EXpert IPTV Test Tools uses the GigE port of the platform. Connect the 10/100/1000 electrical signal with the IPTV to the port with the RJ-45 connector. Note: Refer to the platform User Guide for more information.
Chapter 5 Using the Graphical User Interface This chapter describes the graphical user interface of your EXpert IPTV Test Tools application. The EXpert IPTV Test Tools allows you to start a test, connect and disconnect to IPTV streams, program and use Set Top Box, view information about the stream, view IPTV metrics and statistics, view or print test results, and more. Main Window Start the EXpert Test Tools IPTV application.
Chapter 6 6.1 Setting the IPTV Test Setup Interface The Expert IPTV Test Tools setup has factory defaults. Changing these defaults is necessary only if any of the following parameters is required for login process: • • • • • MAC address IGMP version change Static IP address or DHCP client-Vendor Class ID Changes in the Thresholds settings The default Ethernet interface is: • • • • 6.
The TR101290 allows configuration or Priority 1 and 2 parameters from a separate menu as shown to the right. These color coded thresholds will then trigger the corresponding flags in the Summary pan. Unchecking any parameters removes it from the active metrics. Unchecking all parameters will result in the TR101290 Errors of Summary. 6.3 Manage Channel List Click on Manage channel list. · · · Enter New Group name as a channel list. · Select either Multicast channels or VoD streams.
For VoD streams: · Enter New Channel Number, Name and rtsp uri and press OK. · Repeat the above step for each additional channel (or rtsp uri) to be added to the multicast (or VoD) group. When Groups are exported a file with extension “.ExfoChannels” is created. Groups can be imported only from files with this “.ExfoChannels” extension. • To import a Group click on “Import all Groups” then select the file from the desired folder and open it.
Chapter 7 Running IPTV Tests 7.1 Simultaneous Testing of Multiple Channels 7.2 Passive Test The Passive Test allows monitoring of any IPTV streams present at the interface, for quality of service and video preview.
The Passive Test starts automatically after depressing the and upon detection of a valid IPTV stream(s). All detected valid streams will be displayed in the Test Log box and marked as Passive. • • • • • Channel whose metrics and preview are currently displayed is underlined To view metrics and preview of another channel click on it in the Test Log box. Check the Summary metrics for a quick signal quality check. Click on the tab of a specific metrics of interest to view details.
7.3 Set Top Box Emulation Test The Set Top Box Emulation Test allows IGMP or RTSP join& leave requests to one or multiple IPTV streams. Once the stream(s) become detected and synchronized to the test metrics start and live video preview is available on non-encrypted streams. Number of channels that can be tested simultaneously is limited to 10. Exceeding this number will generate an ERROR message. Live Preview is limited to one stream.
For VoD streams (uri’s): · Choose the RTSP uri to be tested from the Channel List in the STB · Click on Play button of the chosen channel in the Set Top Box. This will initiate RTSP join request for this unicast channel. Once the stream in this is detected it will show up in the Test Log box as active. Repeat this process for all channels to be tested. To stop the test of the specific stream press or disconnect the Ethernet cable. 7.
Chapter 8 Getting IPTV Metrics The channel whose metrics are currently displayed is underlined in the Test Log. Active streams count Terminated streams count # of passed tests # of tests with warnings # of failed tests 8.1 Basic IPTV Metrics Test Check the Video Description Information for the stream characteristic and reference data.
· Check Summary metrics for a quick signal quality. Summary provides a list of industry most used parameters for quick evaluation of IPTV service quality such as MOS Score, PCR Jitter, Video Packet Loss, TR 101290 and IGMP Latency( zap time).
8.2 · Live Stream Preview Video and Audio preview of the channel whose metrics are currently displayed can be enabled at anytime in the main test window. The preview can be toggled to full screen size or stopped all together and audio can be turned on or muted.
8.3 Advanced IPTV Metrics Test 8.3.1 Video Perceptual Quality Metrics As described in the technical reference section Chapter 6.1, the Perceptual Quality Metrics are calculated on the selected video stream to provide Mean Opinion Score (MOS) and related parameters. Video Perceptual Quality provides the most essential QoE scoring metrics such a Video MOS scores that results from computation of a complex formula (see Technical Overview for details).
8.3.2 Transport Packet Metrics Transport Packets are MPEG-TS packets that carry Packet Elementary Stream (PES). Jitter Metrics focus on the PCR Jitter which is defined as Time Stamp arrival time jitter. Statistics of these MPEG-TS Packets such as lost, discarded, corrected, out-ofsequence and duplicated packets allow detection of this major source of video picture degradation. PCR Jitter is a major contributor to loss of frames due to router or STB buffer overflow.
Definitions: Stream RTP Transport Metrics for MPEG-2 Transport over RTP Stream Packet Transport Metrics 31
8.3.3 MPEG-TS TR 101290 Priority 1 TR 101290 First Priority lists Loss and Error counters that are essential for video decodability. TR 101290 Second Priority lists Error Counters recommended for continuous or periodic monitoring.
MPEG_2 Transport Stream TR 101290 Priority 1 Metrics 8.3.4 Audio Description and Perceptual Metrics Information Audio Description Information is similar to Video Description Information providing essential reference information about the stream. Audio Perceptual Quality Metrics are MOS scores with subjective test content calculated with a specialized VQMON audio algorithm.
Definitions: Audio Stream Description Audio Perceptual Quality Metrics: Audio bandwidth Metrics: 34
8.3.5 Video Frame Metrics Video Frames (MPEG-TS) statistics provide the total number of Received and Impaired frames I, P, B and optional SI and SP. This breakdown allows better diagnostics of the distorted video. Packet statistics such as Packet Lost, Packets Discarded and Packets Impaired correspond to the MPTEG-TS frame statistics and they allow more detail breakdown of the diagnostics.
Definitions: Video Frame Metrics 36
8.3.6 Video Bandwidth Video Bandwidth of I, P, B, SI and SP frames provides a useful information for traffic engineering. Looking and MOS and other metrics one can determine how much less or more bandwidth to add or reduce to maintain the quality goal and bandwidth utilizations at the same time.
8.3.
Chapter 9 9.1 Generating and Viewing Test Results Test Results Log 9.1.1 Accessing Test Results Access to the Test Results is available from 2 locations: 1. Results button shown to the right OR 2.
Test Results generated by Results button or button produce the following log: Double-clicking on the selected test record produces the metrics screen where all test metrics are accessible from the tabs: 40
Here is an example of the Charts screen produced for the single test record. • To generate a pdf report click on button and wait for the Summary PDF report to be generated.
The report start with the summary page followed with test metrics four pages long as shown below: 42
Appendix A The IPTV Video Stream is subjected to multilevel analysis as shown here: A.1 Understanding IPTV Video Perceptual Quality * The perceptual quality of video transmitted across IPTV networks is susceptible to degradation from a number of transmission network sources including, frame errors caused by packet loss, discard of packets due to excessive delay/jitter, and discard of packets due to arrival sequencing errors.
cause obvious distortion or may not even be noticed by the end user, depending on which video frame types are impaired. In addition, impairments can be introduced during the encoding/decoding process, by the codec itself or an inappropriately low bitrates. The video content (e.g., level of detail and motion onscreen) can also have a significant impact on the visibility of problems. Furthermore, perceptual quality is affected by subjective factors including human reaction time and the ‘recency effect’.
As a frame often spans multiple packets, and a typical video stream includes interpolated frames (P-frames and B-frames), a given packet loss rate can result in a frame loss rate six times higher [9]. See Figure 2-1 above. In order to accommodate IPTV transmission network delay and low levels of delay variation, a playout buffer is used to temporarily store incoming frames. For streaming video, such as DVB or IPTV, it is permissible to apply arbitrary delays, and hence the playout buffer can be quite large.
For inter-frame or motion-based coding (P and B frames), motion vectors are determined for each block and encoded. As for intra-frame coding, errors can render a whole slice or frame unusable. In simple inter-frame coding systems, the loss of one I or P frame can make all subsequent frames unusable until the next I frame is received—resulting in a significant period of degraded, frozen, or blank video. Note: the H.264 (MPEG-4 AVC) codec standard introduces two new frame types, Figure 2-2.
A.1.1.2 Impact of Packet Loss on Specific Video Codecs As shown in Figure 2-3, a simple non-robust video stream can be severely degraded with even low levels of packet loss due to the error propagation effects described above. Peak Signal-toNoise Ratio (PSNR) is an objective measurement of video service quality comparing the maximum power of the video signal to the power of corrupting noise affecting the signal.
Error mitigation algorithms are being increasingly applied to help to compensate for packet loss [11][12]. Methods include: Forward Error Correction (FEC) - redundancy is applied to the data stream to allow some proportion of lost or errored packets to be replaced. Interleaving - in which the video stream is split into alternate frames and each encoded separately. Macro-block error concealment - spatially corresponding macro-blocks are copied from the previous frame.
A.1.2.1 Impact of Coding Bitrate on Video Quality For a typical MPEG-2 encoded video stream with standard resolution 720x486, GOP sequence IBBPBBPBBPBBPBB, at 30 frames per second, the mean square error (MSE) due to bitrate can be approximated by: MSEbr = 0.00001 + 1.5 / (B + B2 / 30000). Where B is the bitrate in kilobits per second. The corresponding peak signal-to-noise ratio (PSNR) value for the frame can be computed by PSNRbr = -10 log10MSEbr.
The following examples illustrate the impact of the coding bitrate on video quality. Both images show the same frame from a video sequence encoded with MPEG-2 at a resolution of 720x480, at 30 frames per second. In Figure 2-5 the sequence was encoded at a bitrate of 5000 Kbps (610KB/s). Figure 2 -5 Still frame from MPEG-2 video sequence encoded at 5000Kbps Figure 2-6.
In Figure 2-6, the sequence was encoded at a bitrate of 1127Kbps (138KB/s). The use of coarser quantization conserves bandwidth, but creates distortion that impairs overall image quality throughout the entire video sequence. A.1.2.2 Performance of Video Coders There are many standardized video coding algorithms, such as ITU-T H.261, H.263, H.264, ISO/IEC MPEG-1, MPEG-2 and MPEG-4, AVS, VC-1, etc.
IPTV applications generally support video encoded with SD resolutions of 720x486 (30 Hz) or 720x576 (25 Hz), or HD resolutions of 1280x720 (720p) or 1920x1080 (1080i) at an average bitrate of 3 Mbits/sec or higher. Typically, the number of bits spent on coding a P-frame is about 20% of the number required for an I-frame, whereas a B-frame takes about 5% of the bitrate consumption of the I-frame.
VQmon/HD’s quality analysis algorithm considers these temporal phenomena in order to calculate perceptual quality scores that correlate as accurately as possible to scores obtained from subjective tests of live viewers. A.2 VQmon/HD Quality Analysis Algorithm * This section describes VQmon/HD’s video and audio quality analysis algorithms and lists some of the key metrics reported by VQmon/HD as part of the Telchemy Video Quality Metrics (TVQM) data set. A.2.
Figure 2-7. VQmon/H D video stream quality analysis algorithm A.2.1.1 TR 101 290 Metrics Collection VQmon/HD collects and reports the full set of Priority 1 and 2 metrics described in TR 101 290 for the measurement and analysis of MPEG-2 Transport streams. A.2.1.2 Playout Buffer Emulator VQmon/HD’s playout buffer emulator component detects lost, duplicate, and out-of-sequence packets and measures packet-to-packet delay (jitter) levels, reporting PPDV (RFC3550) and MAPDV (ITU-T G.1020).
A.2.1.4 Frame Type Detection VQmon/HD identifies individual I, P, and B frames in the GoP and measures the packet loss rate and loss distribution occurring in each frame type. For unencrypted video streams, VQmon/HD performs picture header decoding to identify individual frames, GoP size, and frame rate. For encrypted/scrambled streams, heuristic algorithms are applied in order to detect frame boundaries and measure frame size. As mentioned in Section 2.1.1.
A.2.1.7 VQmon Markov Model (VMM) VQmon/HD uses a four-state Markov Model to gather and report packet loss statistics for “burst” periods (where quality is significantly degraded) and “gap” periods (periods between each burst interval when quality is relatively unimpaired). VQmon/HD calculates quality metrics in these burst and gap states, and then combines them to generate the overall quality score on user experience.
Figure 2-8. VQmon Four-state Markov Model diagram A.2.2 Audio Stream Analysis VQmon/HD’s audio quality analysis algorithm performs real-time analysis of audio stream packets and generates perceptual quality scores (MOS-A) and other metrics corresponding to those produced by the video quality analysis algorithm. Like the video stream analysis algorithm, the audio quality analysis algorithm calculates the impact of time-varying impairments (i.e.
A.2.3 Telchemy Video Quality Metrics VQmon/HD provides real-time perceptual quality scores, performance statistics, and extensive diagnostic data for monitored video streams in the form of the TVQM™ (Telchemy Video Quality Metrics) data set.
Table below lists some of the perceptual quality metrics reported by VQmon/HD, including acceptable ranges for each. (A complete list and description of the TVQM Video Quality Metrics reported by VQmon/HD is provided in Appendix C.) A.2.3.1 Mean Opinion Scores (MOS) VQmon/HD reports estimated Mean Opinion Scores (MOS) for picture quality (MOS-V), audio quality (MOS-A), and multimedia quality (MOS-AV) for each monitored video stream.
For picture quality, VQmon/HD reports both Relative MOS-V and Absolute MOS-V scores: • Relative MOS-V is an estimated perceptual quality score that considers the effects of codec/quantization level, the impact of IPTV impairments (e.g., packet loss) on the GoP structure and video content, and the effectiveness of loss concealment methods—but does not consider the image size/resolution, frame rate, or scanning method (interlaced vs. progressive).
A.2.3.2 VQmon/HD Video Service Transmission Quality Metric - VSTQ VQmon/HD produces a video services quality metric, VSTQ (Video Service Transmission Quality), which is a codec-independent measure of the ability of the bearer channel to support reliable video. This video service quality metric is expressed in the range of 0.0 to 50.0, as defined in [14]. VSTQ can be calculated by a mapping function from Peak Signal-to-Noise Ratio PSNR values as follows: VSTQ = max(0, min(50, (PSNR - 12) * 1.
A.2.3.3 Degradation Factors To facilitate troubleshooting, VQmon/HD has the ability to obtain a breakdown of factors contributing to quality degradation.
A.3 • • • • • • IPTV Protocols IPTV uses a multilayer protocol stack to deliver the media contents. The first 3 layers are typical for IPTV transmission. The UDP/RTP session layer is responsible for transferring packets between the sender and the receiver. The MPEG-TS transport stream layer combines multiple media streams ( video, audio, data) into a single program transport stream. The PES layer assigns video and audio to specific packet streams.
MPEG frame is fixed at 188 byte, with 184 Data Payload and 4 Byte Header. The 13-bit PID indentifies Packet Elementary Stream (PES). The PES is much longer than the MPEG frame so it is divided into segments over multiple MPEG frames.
The Packetized Elementary Stream is converted into the Video Elementary Stream ( MPEG-2 transport stream) 67
• • • • • • • • • • PES header contain information about the contents of the PES packet. Variable length packets typically up to 64 Kbyte but may be longer PTS and DTS allow a decoder to reconstruct the video from I, Band P frames sent by encoder. If header information is corrupted, entire PES packet will be lost. Fixed Length packets, multiplexes many PES packets.
• • • PAT lists all programs available in the transport stream with their program ID (PID). Each program has a PMT that lists the elementary streams for that program. Errors in PMT, PAT, PID/PSI(Packet Identifier/ Program Specific Information) Errors will cause the set top box lose contact with the stream. These errors may originate at any of the MPEG transport multiplexers when new streams are inserted.
A.4 PCR Jitter PCR (program counter reference) timestamps is generated by the MPEG-2 encoder and received throughout the subsequent links in the network at least 100 milliseconds apart. The decoder uses the PCR to lock its own 27 MHz clock to the encoder system time clock (STC). This 27MHz clock is very sensitive to variations caused primarily by packet transmissions delays. Therefore, measurement of the PCR timestamp arrival time variation called commonly “PCR jitter” is essential.
A.5 IGMP Latency vs. Zap time The zap time is the total duration from the time viewer presses the channel change button, to the point the picture of the new channel is displayed, along with corresponding audio. These kind of delays exist in all television systems, but they are greater in digital television and systems that use the Internet like IPTV. Human interaction with the system is completely ignored in these measurements, so zap time is not the same as channel surfing.
IGMP is the signaling protocol used to access broadcast video services that use a multicast network design to efficiently manage network bandwidth. In this implementation, a join message is sent from the STB to the network. The join message asks the network to send the requested program or channel to the STB by joining a multicast group carrying the desired broadcast channel. IGMP latency, then, is the time between when the join message is sent and the first video packet is received by the STB.
The IGMP latency plus the time it takes to fill the decode buffer and to decode and display the content is the total user experience time. However, the buffer fill time and the decode time are functions of the network architecture and are not variables. This total time is called Zap Time.
Appendix B Technical Specification Average GOP length Max GOP length Average gap of I frame Frame width Frame height Frame rate interlaced Average number of slices in I frame Reference clock rate Average video bandwidth Average packet size Physical Layers Supported 10/100/1000 Ethernet, Wi-Fi 802.11 b/g/n. Recognized Video Compression Standards Codecs unknown video motion JPEG video MPEG-1 video MPEG-2 video ITU-T H.261 video ITU-T 1996 version of H.263 video ITU-T 1998 version of H.263+ video ITU-T H.
Video Jitter Frame inter arrival jitter I frame inter arrival jitter Average frame arrival delay Peak frame arrival delay MPEG2-TS TR101290 Priority 1 last errors TS sync loss count Sync byte error count PAT error count PAT2 error count Continuity error count PMT error count PMT2 error count PID error count Video Scene Analysis Metrics Instantaneous detail level Instantaneous motion level Instantaneous panning level Static image proportion High detail proportion Low detail proportion High panning proporti
Video Frames I,P,B,SI,SP – Frames received Frames impaired % frames impaired Packets received Packet lost Packet discarded % packets impaired %packets impaired by error propagation Except for I and SI Video bandwidth of I,P,B, SI and SP frames – Average video bandwidth Max video bandwidth Histograms (charts) Up to two charts from any metrics LAN Port - 76 IP address Downstream rate Upstream rate
Troubleshooting Contacting the Technical Support GroupTo obtain after-sales service or technical support for this product, contact EXFO at one of the following numbers. The Technical Support Group is available to take your calls from Monday to Friday, 8:00 a.m. to 7:00 p.m. (Eastern Time in North America). Technical Support Group 400 Godin Avenue Quebec (Quebec) G1M 2K2 CANADA 1 866 683-0155 (USA and Canada) Tel.: 1 418 683-5498 Fax: 1 418 683-9224 Support@exfo.
Glossary Perceptual Quality Metrics Metric Description MOS-V Video MOS, a 1-5 score that considers the effect of the video codec, frame rate, packet loss distribution and GoP structure on viewing quality MOS-A1 and MOS-A2 for 2 codecs that are present in some streams Audio MOS, a 1-5 score that considers the effect of the audio codec, bit rate, sample rate and packet loss on viewing quality MOS-A1V Audio-Video MOS – a 1-5 score that considers the effect of picture & audio quality and audio-video sync
Video Stream Metrics The Video Stream Description provides information on the type of codec being used, Group of Pictures structure and length, image size and other key factors. Video Stream Description Metric Description Codec type Type of codec (e.g. MPEG4) GoP type Group of Pictures type (e.g.
Transport Metrics Packet Loss Metrics provide essential data on IPTV packet loss before and after the effects of error correction (such as FEC or Reliable UDP). Burst and gap statistics provide valuable insight into the time distribution of lost and discarded packets.
TR101 290 metrics provide green LED ON/OFF information on certain key error types that occur with MPEG Transport protocols, and are useful in identifying and resulting these error conditions.
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