MPEG-2 Transport Stream Analyzer
MPEG-2 Transport stream analyzer for content validation and quality assurance
Designed for next-generation media processing and delivery workflows
Advanced validation features and seamless integration of the analyzer into an automated workflow helps deliver error-free MEPG-2 TS more efficiently
Introduction
MPEG-2 Transport Stream is a widely used container format for transmission and storage of compressed video. MPEG-2 TS specifies how for a given TV program or a Video On Demand file/asset, the audio, video, and other auxiliary data are to be multiplexed. An MPEG-2 TS can contain multiple videos and the standard allows packetized elementary streams to form a complete transport stream. For a Video Service Operator, this translates into efficient use of bandwidth since multiple TV programs can be sent via a single channel. MPEG-2 TS continues to be the de-facto video delivery standard for ATSC, DVB, and IPTV video systems and is also used by some of the OTT video providers.
Transport Streams contain the actual video and audio packets as well as key information regarding each and every video service/program so that the decoders can properly decode and present the data to the viewer. The elementary streams of audio and video are encapsulated to form a packetized elementary stream. After packetization, they are multiplexed into a serial stream known as a transport stream. At a time, 188 Bytes packet is transmitted. On the receive side, the stream is decoded and individual audio and video data is extracted and displayed on the user device.
Following are some of the critical errors and important tables and parameters that contain data of significant consequence, and therefore, must be monitored and analyzed to ensure flawless delivery of MPEG-2 Transport Streams.
PID — Program ID
PID is a unique identifier for the program and tells the decoder which program a particular elementary stream belongs to.
PAT & PMT — Program Association Table and Program Map Table
A transport stream’s PAT a listing of which PIDs contain the program map tables (PMTs). The PMT contains the list of audio and video PIDs that comprise programs in the transport stream. It also has a Program Clock Reference for each program.
Packetized Elementary Streams (PES)
The PES packets contain the actual audio and video data
PCR — Program Clock Reference
PCR is used for the synchronization between the encoder and the decoder clock. If this synchronization is not properly maintained video-audio will be out of sync, video might not be displayed correctly, directly affecting the viewer quality of experience
T-STD (Transport Stream Target Decoder) for buffer analysis
In MPEG-2 TS, since different types of data are multiplexed and come in different packets, there is a possibility of introducing a delay in the transmission. This requires a proper buffering mechanism at both encoder and the decoder points. The MPEG-2 standard contains specifications for calculating buffer size. E.g. the VBV parameter specifies how much buffering is needed for a given elementary stream. Both the encoder and the decoder must adhere to these specs for proper synchronization.
TR 101 290
The TR 101 290 guidelines define the measurements that are required for Transport stream integrity. There are three levels of priority for the errors in a transport stream. Priority 1 error basically is a no-go; the signal might be illegal, with major faults such that the picture cannot be displayed. Priority 2 errors occur when the TS may be structurally fine but the individual program cannot be played correctly. Priority 3 errors are where the main audio-video data can be presented correctly but there are errors in the supplemental data.
Need for a Transport Stream Analyzer
Due to the complexity involved in packetizing and multiplexing elementary streams and the transport streams, tools that provide deep visibility into transport streams have become essential for ATSC, DVB, and IPTV video providers. The need for such tools is needed to troubleshoot streaming media as well. OTT video is close to becoming the dominant media delivery format. E.g. Apple HTTP Live Streaming (HLS) protocol uses MPEG-2 TS for encapsulating the ABR segments.
Errors in the transport stream will result in issues such as video tiling, lip sync errors, and audio problems, thus directly affecting viewer’s quality of experience.
MPEG-2 TS analyzers provide critical insights into a transport stream’s logical structure, including teletext, subtitling, and the actual audio and video content. This information helps with error detection and troubleshooting of compressed media.
Introducing VEGA Vista: A TS analyzer for the next-generation video workflow
MPEG compression systems are inherently complex and prone to errors as the video goes through multiple processing stages, often requiring a full decode and re-encode, before it reaches the final destination. Although the MPEG-2 Transport stream standard has been in existence for more than two decades and has largely remain unchanged, video equipment and service providers are dealing with new and evolving test environment and delivery workflows. We have seen new audio and video formats emerge such as HEVC, AV1 etc. These new formats data delivery formats require organizations to test the compressed video on a continuous basis. On top of this, there is an ever-increasing growth in content volume, which necessitates a more efficient way to test transport streams. Typically, transport stream analyzers are available on a stand-alone hardware that perform either off-line or realtime MPEG-2 TS analysis. We are seeing a new trend in the industry where professionals involved with content preparation and delivery prefer automated workflows in a so-called headless environment, which is driving the shift towards software-based, more powerful analyzers that can perform fast analysis on large volumes of data and support VM and Cloud environments.
Interra Systems’ VEGA Vista is a software application for checking end-to-end compliance and performing debug and analysis of Transport Streams (TS).
Using VEGA Vista, the user can create customized profiles for different types of errors using a GUI and get conformance reports as output in XML/HTML format. Vega Vista makes it easy to deploy it in a headless system, as it can run as a separate microservice, performing MPEG-2 TS file validation.
Features and Benefits of VEGA Vista
Accurate, comprehensive analysis of large volumes of transport streams in one go
Performa analysis of elementary streams contained inside the transport stream
Configurable Command Line Interface
CableLabs 3.0 checks along with elementary header level checks
Comprehensive Reports in XML and HTML formats for PID summary, Multiplex summary, PID properties, and Stream error summary
Comprehensive formats support
Transport Streams: ATSC, DVB, CableLabs 3.0
Audio-Video Elementary Streams: HEVC, H.264, MPEG-2, AAC, Dolby AC3/EAC3
Data: CC 608 & 708, SCTE 20, SCTE 35
High performance software for on-premises, cloud, or virtual deployment
A typical use cases for an MPEG-2 TS analyzer
A TV network receives and creates new repositories of MPEG-2 Transport stream files on a continuous basis. Many of the files received from content providers undergo decode and re-encode and therefore, these files need to be checked for compliance and quality against a defined profile. Different profiles are created that contain fine-tuned requirements for various types of data such as Closed Captions, SCTE-35 messages, audio loudness, buffer analysis etc. The MPEG-2 TS files may contain different types of elementary audio and video such as HEVC, H.264, and Dolby DDPlus etc. A profile to check elementary stream header checks is created for encoder compliance. Depending on the values defined in the profile and the actual values reported by the analyzer, the file is either a “Pass” or a “Fail”. Files that don’t meet the specifications are forwarded to the appropriate group for further action. Some of the parameters that are checked are:
Video Resolution
Audio bit rate for each service in the transport stream
Video bit rate for each service in the transport stream
TR 101 290 Errors
PCR accuracy and Drift rate
PSI-SI information for each service
Closed Caption existence / Syntax check
Graphical reports for T-STD analysis showing buffer occupancy etc. are checked for buffer underflow and overflow conditions.
Continuous analysis of Error logs and other reports provided by the analyzer are studied to assess encoder and decoder performance and fix errors
Different templates/profiles are created on an on-going basis to show Service Level Agreements (SLA) compliance. The SLAs might include Closed Captions, delivery of the program at the agreed-upon bit rate etc.
Depending on the reason for the fault, files are remuxed, while maintaining the integrity of the encapsulated audio and video elementary streams. A dockerized version of the software is deployed for the cloud-based workflow. For encoder and QA teams that create software builds based on the results of the tests, the analyzer application can be invoked on any available cloud machine, on demand. This enables geographically dispersed teams to work collaboratively to analyze, debug, troubleshoot, and ultimately, prepare error-free transport streams that conform to the user-specified content delivery profiles and quality. Depending on the amount of MPEG-2 TS files to be tested per day, multiple files can be run on multiple instances of the analyzer, speeding up the validation process.
VEGA Vista Solution Benefits Summary
VEGA Vista decodes the entire MPEG-2 TS and presents in a logical structured fashion so that the user can drill down to the required information. Detailed reports for parameters that affect QoS and QoE such as frame rate, bit rate, buffer overflow and underflow etc. can be evaluated in a completely script-driven, automated environment. Vega Vista provides a complete set of checks and analysis features to help media companies assure MPEG-2 compliance as part of post-encoding, transcoding, or postproduction workflows. With Vega Vista, video service providers can perform comprehensive analysis of MEPG-2 TS for better Quality of Service and Quality of Experience.
VEGA Vista is easy to incorporate into existing or new workflows as it can be installed on any on-premises server or in the cloud environment for ultimate scalability and flexibility. Professionals involved with research and development, QA and video delivery, will find in Vega Vista an indispensable analyzer that will expedite development, identification and troubleshooting of MPEG content. Vega Vista is part of the Vega Media Analyzer from Interra, renowned for in-depth analysis and accuracy of all popular video compression formats.
To learn more about VEGA Vista, please visit https://www.interrasystems.com/Vega-vista.php
About Interra Systems
Interra Systems is a leading provider of Video QC, monitoring, and analysis solutions, helping media companies deliver video with better quality of service and quality of experience. Interra’s video analysis tools go to the deepest levels of compressed video to provide critical debug information and quality analysis. The acclaimed Vega analyzer continues to be the most popular and powerful video analyzer platform with support for a wide range of audio and video standards.
