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Validating the real-time operation and performance of MPEG signals can be difficult, especially when the MPEG transport stream contains various video compression formats including the new MPEG-4 part 10 (AVC) coding format. To help perform testing of MPEG transport streams, test systems can be divided into different types of analysis which include; full analysis, quick-view, and command-line analysis.
The full analysis provides program specific information along with the data that defines certain elements of the characteristics of program media (such as the video, audio and meta descriptive components of a television program). Full analysis can provide detailed information in text (report) or graphics (graph) formats. Quick-view analysis can display the contents of the transport stream according to the initial PSI. Command-line analysis can process and analyze multiple files that are submitted for analysis.
Manzanita has simplified the testing of an MPEG transport stream by developing the enhanced transport stream analyzer software tool, MP2TSAE 4.0. Test technicians simply select the input stream, configure the analyzer, define the transport analyzer, select the AVC frame rate option, and run the analysis.
Input Transport Stream Selection
The input stream that is to be analyzed may be a stored file or may be captured from a device that is streaming live over IP. The technician selects the network source and enters the IP address or hostname of the device that is the source of the transport stream (in binary format), and enters the port number of the source (assigned to the streaming channel).
The technician can then enter the path and name of the file where the transport stream will be captured (stored). Limits can be set on the maximum size of the stored file (capture size). |
Analyzer Configuration
The analyzer may be configured to perform specific types of analysis. The first time MP2TSAE is operated, a default configuration is provided to allow for immediate use of the software tool. Configuration settings may be stored for different types of tests. Some of the configuration options include stream mode analysis (MPEG, ATSC, DVB), custom table definitions, profiles, error report lists, and abort and record limits.
Transport Options
The transport option identifies the transmission bit rate and timing information that is used by the transport stream. MP2TSAE transport options include transmission rate and packet interval. The transmission rate can be set to auto, fixed, and variable (VBR). The auto mode selects a transmission rate that is determined by the program clock reference (PCR) timebase. The fixed rate allows the user to specify a fixed value. The VBR enables the analyzer to adapt the transport rate between every two
PCRs.
The packet interval option identifies whether the time interval between sync bytes is manually set or automatically determined from data in the transport stream. The packet interval option determines how the analyzer reports loss of sync errors.
AVC Frame Rate Option
If the MPEG transport stream is carrying elementary streams that contain AVC video, the AVC frame rate option is set. When the Force Standard AVC Frame Rate Option is enabled, the Analyzer will use a standard MPEG-2 video frame rate in the analysis instead of the one that is encoded as a ratio in the syntax of the AVC stream. It uses the rate from the set of discrete frame rates that are supported by MPEG-2 closest to the rate computed from the ratio in the AVC stream. This feature can be enabled to correct the accumulating errors that result when the frame rate ratio encoded in an AVC stream does not exactly match the effective frame rate. |
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Running an Analysis
After the input has been selected, configurations set, transport options set, and the AVC option chosen, the technician simply selects the Run Analyzer button. This starts the analysis and a progress bar appears. With a single pass of an input file, the analysis can provide a transport stream summary, error warnings summary, and PID summary. Advanced tools can be used to inspect the results and produce a report file. Each PID stream can be analyzed for its PSI components (PAT, CAT, or PMT). The analysis information can contain:
- Number of errors/warnings reported in each PID stream instance.
- The program number of the program to which each PID stream instance is mapped. If the stream is not part of a program, it is blank.
- Type of data (content) in the packet payload of each PID stream instance.
Number of transport packets in each PID stream instance.
- Transport packet rate of each PID stream instance. This data rate includes all transport packet overhead, including transport, adaptation and PES headers.
- Payload rate of each PID stream instance. This data rate does not include packet overhead, and in the case of elementary PIDs, is the same as the
elementary stream rate.
- Additions or deletions of PID stream instances.
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Figure 1 shows the graphical user interface (GUI) of MP2TSAE 4.0. The first window (top left pane) identifies the streams within a transport stream. The second window (bottom left pane) provides descriptions of the programs and their associated streams. The configuration and stream information is displayed in the third window (top right display). A detailed list of packet errors and timing is provided in the fourth window (bottom right pane).
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Manzanita Systems is focused on providing innovative solutions for MPEG-based systems. Manzanita's powerful and versatile products have enabled its customers to finally take advantage of the features, flexibility, and interoperability inherent in digital video and the MPEG standard. Through the development of its signature MPEG-2 Transport Stream Analyzer, Manzanita has built a strong foundation in MPEG compliance issues.
14269 Danielson Street, Suite 200
Poway, CA 92064, United States
Tel: +1-858-679-8990
Fax: +1-858-679-8991
www.manzanitasystems.com
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