Mividi TSM100 is a leading professional IP video analyzer and monitor. With the addition of the MPEG-DASH support, it provides a professional tool for analyzing and monitoring live and VOD MPEG-DASH streaming.
Figure 1: MPEG-DASH Analysis and Monitoring
Overview
Internet streaming video becomes increasingly popular because it can deliver video content to any device at any time. A number of streaming protocols are available for transporting video over IP network. In recent years, because more types of devices are used to watch videos in addition to traditional TV sets, adaptive bitrate streaming technique is often selected so client devices can choose a specific stream among multiple alternate streams based on device resolution and connection bandwidth.
Dynamic Adaptive Streaming over HTTP (DASH) is an adaptive bitrate streaming technique that stream media content over the Internet using HTTP web servers. The media content is divided into segment files, and a media presentation description (MPD) file describes segment information including timing, URL, media codec and characteristics such as video resolution and bit rates. Segments can contain any media data, and MPEG specification provides specific guidance for use with two types of containers: ISO base media file format (e.g. MP4 file format) or MPEG-2 Transport Stream.
DASH breaks the overall stream into a sequence of small files. The client app downloads the files using HTTP protocol and resembles the files into a continuous stream. Since the downloading uses only standard HTTP transactions, DASH is capable of traversing any firewall or proxy server that lets through standard HTTP traffic.
However, using IP network to transport media data can introduce transmission errors such as delay, jitter and packet loss. Video delivered over the Internet which the video provider does not have full control can exacerbate the problem. Additional errors may also exist on video source and processing causing overall performance degradation for video consumers.
The Mividi TSM100 supports QoS monitoring of DASH streaming. The system can simultaneously monitor over 100 DASH streams from one or more video servers, and perform extensive analysis on HTTP transfer status, MPD file syntax, downloading delay, and audio and video qualities.
The system is designed for 24 x 7 remote operations. All errors detected by the system are saved in the database and alarms can be generated. Multiple reports can be generated to summarize the stream status and error conditions over time.
Application Example
Figure 2: MPEG-DASH Video Service Monitoring Using TSM100
DASH Analysis
The system parses and analyzes MPD files. Element tags and attributes are verified for standard compliance. Each media stream segment is downloaded. The download time and media time are compared and bitrates are calculated. When average download time exceeds media time, delay is reported. A number of media file and session parameters are recorded in the database, including segment URL, file size, and file downloading time. The synchronization of alternate media streams is monitored since DASH media files are normally not multiplexed and are streamed independently. All detected errors are also saved in the system database and reports can be generated.
Video, Audio, Subtitle Analysis
Although DASH stream segments can contain any media data, most real-world applications use MP4 or TS streams. The TSM100 systems will continuously decode all downloaded video, audio, and subtitle data and monitor the following errors:
- Monitors the loss of each alternate elementary stream.
- Continuously decodes video and checks black and frozen frames
- Continuously decodes audio, calculate loudness according to ITU BS.1770-5, and checks loudness errors
- Check bitrate based on user-specified profiles and report bitrate out-of-bound and video/audio errors
In addition, the system can display video thumbnails, audio volume bars and subtitle content in real-time.
Remote User Interface
Two client applications are provided for viewing test results and control the monitoring system remotely. An easy-to-use Windows® desktop application can dynamically display all test results and play video and audio in real-time for visual verification of Quality of Service (QoS). A web based client application can be used to access test data using Internet. SNMP is supported for error traps and data query.
Error Alarm, Logging and Reports
All errors detected are logged in a database. The logging feature allows the operator to search specific errors based on various searching criteria. Selected errors can be exported to a text file. The TSM100 allows users to create streaming profile, and the system will test the actual input data against user entered profile, report and record any deviations. The system can also be configured to send alarm messages when severe errors occur, such as loss of signal, loss of audio or video stream, black or frozen frames. In addition, a number of reports, including DASH error summary, media file and downloading statistics, as well as AV error summary can be generated.