Glossary

Transport stream fundamentals

MPEG TS (Transport Stream)
The container format defined in ISO 13818-1 for multiplexing digital audio, video, and data into a single bitstream. All content carried by the TS Analyzer is in this format. Each TS is divided into fixed-size packets of 188 bytes.

PID (Packet Identifier)
A 13-bit label in each TS packet header that identifies which logical stream the packet belongs to — video, audio, a specific PSI/SI table, or stuffing. The TS Analyzer tracks errors and bitrate per PID.

Service
A logical combination of elementary streams (video, audio, subtitles, etc.) grouped together under a common name and presented to the viewer as a single TV channel.

Elementary Stream (ES)
A single encoded audio or video stream, carried on its own PID. Multiple elementary streams form a service.

Stuffing
Null packets inserted to fill available bitrate. PID 8191 is reserved for stuffing. Total bitrate minus stuffing equals payload bitrate.

Multiplexer (mux)
A device that combines multiple services and PSI/SI tables into a single transport stream. Most TS quality problems originate at or upstream of the multiplexer.

PSI/SI tables

PAT (Program Association Table)
The root table of a transport stream, transmitted on PID 0. It maps each service number to the PID of that service's PMT. Without PAT, no services can be decoded.

PMT (Program Map Table)
One per service. Describes which PIDs carry video, audio, and other components of that service, and identifies the PCR PID. Referenced by the PAT.

SDT (Service Description Table)
Carries human-readable service names and other descriptive metadata. Displayed in the subscriber device's channel list. SDT_actual covers the current TS; SDT_other covers other TSes in the network.

NIT (Network Information Table)
Describes the physical network — frequencies, modulation parameters, and network identifiers. Used by receiver devices for automatic channel scanning and EPG consistency checks.

EIT (Event Information Table)
Carries EPG (Electronic Programme Guide) data. EIT_actual carries schedule information for the current TS; EIT_other carries it for other TSes. Sections 0 and 1 of EIT carry current and next program information and are mandatory.

CAT (Conditional Access Table)
Transmitted on PID 1 when scrambling is in use. Points to the PIDs carrying EMM streams for each CAS in use. Without a valid CAT, subscriber devices cannot find the keys needed to descramble services.

TDT (Time and Date Table) / TOT (Time Offset Table)
Carry the current UTC time and local time offset into the TS. Used by subscriber devices to set their clock and display correct EPG times.

Timing and synchronization

PCR (Program Clock Reference)
A timestamp embedded in the TS that represents the encoder's clock value at the moment of transmission. The decoder uses PCR to synchronize its internal clock (and therefore all PTS/DTS timing) with the encoder.

PTS (Presentation Time Stamp)
A timestamp in the PES header that tells the decoder when to present (display or play) an access unit. Measured on the same clock scale as PCR.

DTS (Decoding Time Stamp)
A timestamp indicating when an access unit must be decoded — always earlier than its PTS. Present only when decode and presentation times differ (common in video with B-frames).

PCR accuracy
How closely the actual transmitted PCR value matches the ideal value calculated from the constant bitrate. ETSI TR 101 290 requires accuracy within ±500 nanoseconds.

Jitter
Variation in the arrival time of packets. Network jitter causes the inter-packet interval to fluctuate, which can overflow or underflow receiver buffers and trigger CCE errors.

IP network metrics

IPAT (Inter-Packet Arrival Time)
The time between the arrival of the first bytes of two consecutive IP packets containing TS data. IPAT variation is a direct measure of network jitter for IP streams. For RF inputs, IPAT reflects the demodulator's output timing.

MDI (Media Delivery Index)
Defined in RFC 4445. Comprises two metrics: DF (Delay Factor) and MLR (Media Loss Rate). Used to assess the suitability of an IP network for carrying constant-bitrate broadcast streams.

DF (Delay Factor)
The maximum time a payload packet spends in a virtual buffer before being processed. Expressed in milliseconds. A high DF means the network requires a large receiver buffer to handle jitter without packet loss.

MLR (Media Loss Rate)
The number of RTP/UDP payload packets that were not received. MLR > 0 indicates actual packet loss in the network, which will typically also cause CCE errors.

Error monitoring

CCE (Continuity Count Error)
Detected when the cyclic continuity counter in successive TS packets on the same PID does not increment correctly. Indicates packet loss or duplication. The most common and diagnostic error in transport stream monitoring.

TEI (Transport Error Indicator)
A flag in the TS packet header that marks a packet as known-defective. Receivers should discard TEI-flagged packets without generating further errors.

CRC (Cyclic Redundancy Check)
A checksum used on PSI/SI tables to detect corruption. A CRC error on a table means its content may be invalid and should not be used.

Conditional access

CAS (Conditional Access System)
The combination of scrambling, key distribution (EMM), and access control (ECM) that restricts descrambling of services to authorized subscribers.

ECM (Entitlement Control Message)
Carries the keys (control words) needed to descramble a specific service. Transmitted per-service.

EMM (Entitlement Management Message)
Carries authorization data specific to individual subscriber smart cards or groups. Transmitted globally per CAS.

Simulcrypt
A standard (ETSI TS 103 197) for operating multiple CAS systems on the same transport stream simultaneously, with a common multiplexer interface. Most modern CAS deployments use Simulcrypt.

Scrambling
Encryption of the TS payload. Scrambled packets have a non-zero scrambling control field in the packet header.

RF signal quality

SNR (Signal-to-Noise Ratio)
The ratio of signal power to background noise power, in decibels. The most important RF quality indicator for digital television — low SNR directly causes BER degradation and eventual loss of service.

BER (Bit Error Rate)
The proportion of received bits that are in error. In DVB-T2, BER is measured before and after LDPC correction (and after BCH as FER). An acceptable pre-correction BER is below 10⁻⁴; post-LDPC BER should be below 10⁻⁹.

FER (Frame Error Rate)
Error rate after BCH correction in DVB-T2. Should be below 10⁻⁴ for stable operation.

PER (Packet Error Rate)
The ratio of TS packets received with errors to total packets received. A PER above 10⁻⁴ typically leads to significant CCE counts.

SFN (Single-Frequency Network)
A broadcast network where multiple transmitters operate on the same frequency, coordinated to appear as a single signal to receivers. Cell ID in DVB-T2 signaling identifies individual transmitters within an SFN.