|Network Measurements||Command and Control Measurements|
Content quality measurements are the identification and quantity determination of how accurately media can be rendered (displayed) to a user. Some of the key measurements for IPTV for content include delay factor, frame loss rate, media loss rate, rebuffering events, stream integrity, and synchronization offset.
Delay Factor - DF - is a measure of how long a media stream must be buffered to prevent packet loss and it can provide information that determines the amount of jitter that occurs within a network. Packet delay is the amount of time packets take to travel from their source to their destination. Packet delay occurs due to the processing time of routers, traffic congestion and the ability of packets to take alternative routes to reach their destination.
Frame Count - Frame count is the number of frames that have been transferred or received over a period of time. Frame count may be divided into categories of frames such as independent frames (I-frames), predictive frames (P-frames), or bidirectional frames (B-frames).
Frame Loss Rate - FLR - is a ratio of the number of frames (data or image frames) that have been lost in transmission compared to the total number of frames that have been transmitted.
Media Loss Rate - MLR - Media loss rate is a ratio of the number of data packets that have been lost in transmission compared to the total number of packets that have been transmitted over a period of time (such as over 1 second).
Buffer Time - Buffer time is the duration that occurs between the request to setup a buffer storage area to when a buffer begins to provide data to an application or service. Buffer time should be long enough to ensure enough packets are available to continuously supply the application when packet transmission delays occur. For IP media streaming services, buffer time can be several seconds.
Rebuffer Events - Rebuffer events are processes that initiate the setup of a new buffer. Rebuffer events may be triggered when a buffer runs out of data due to long packet transmission delays or a high number of packet retransmission requests. Rebuffer events usually cause video or audio to stop playing on the last available media frame. Like buffer delays, rebuffer events can last for several seconds. Rebuffer events may be measured over a time period (such as 15 rebuffer events per hour).
Rebuffer Time - Rebuffer time is the time period that occurs from when a request for rebuffering is initiated to when media playing starts again. Rebuffer time can be used to calculate the rebuffer ratio, which is the amount of rebuffer time as compared to the amount of play time.
Stream Integrity - Stream integrity is the accuracy of a sequence of data or information as compared to its original information source. Stream integrity may be verifiable through the use of protocol analysis and error detection codes that are sent along with the original data information.
Audio Visual Synchronization Offset - Audio visual synchronization offset is the time duration between the playing of audio information as compared to the associated video components (such as facial characteristics) of a presentation. Synchronization offset can vary due to transmission and processing delays that vary between each media stream.
Transport Stream Rate - Transport stream rate is the amount of data or media information for a combination of control and data transport (the transport channel) that is transferred through a system or to a device over a specific period of time. A transport stream may contain multiple program or communication channels.
Program Stream Rate - Program stream rate is the amount of data or media information in a combination of control and media for a program (such as the audio and video media sources in a television program) that is transferred through a system or to a device over a specific period of time.
Clock Rate Jitter - Clock rate jitter is the undesirable random changes that occur in a clock timing reference signal (such as a program clock rate - PCR)
Jitter Discards - Jitter discard are the number of packets that are eliminated due to excessive fluctuating (jitter) delay time.
Compression Ratio - Compression ratio is a comparison of data that has been compressed to the total amount of data before compression. The higher the compression ratio, the more sensitive the media is to bit errors, delays, and packet loss. Content quality measurement systems such as V Factor may use compression ratio as a factor for the determination or rating of quality level.
Protocol Conformance - Protocol conformance is the ability of a device or system to communicate and process commands according to the syntax (structure) of a protocol specification or its rules.
Program Transport Stream - A program transport stream is the combination (multiplexing) of multiple media streams (typically audio and video streams) on a signal transport channel. IPTV systems may measure various components of a transport stream including table (program data) errors, continuity count, and synchronization loss.
Image Entropy - Image entropy is a measure of the amount of information that is contained within an image or display sequence. A high image entropy level usually indicates a higher level of image complexity or image objects. Image entropy may be used as a factor in determining the amount of compression that can be used (less entropy, more compression).
Missing Channels - Missing channels are programs or data streams that are not available or cannot be received by recipients. A test set or network probe may monitor for missing channels to determine where a stream or group of streams are lost (ended) within a network.
This book explains how to
monitor, test, and diagnose IPTV systems and services. Covered are the
quantitative (packet loss, error rate) and qualitative (perceptual) quality
measurement and control processes. Discover how quality of experience (QoE) can
be very different than traditional quality of service (QoS) measurements.
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