An MPEG-TS packet is 188 bytes: a 4-byte header, optionally followed by an adaptation field, then payload.
| Field | Bits | Notes |
|---|
| Sync Byte | 8 | Fixed 0x47, lets a decoder lock onto the stream. |
| Transport Error Indicator (TEI) | 1 | 1 = demodulator flagged an uncorrectable error. |
| Payload Unit Start Indicator (PUSI) | 1 | 1 = payload’s first byte starts a new PES/PSI unit; 0 = continuation. |
| Transport Priority | 1 | 1 = higher priority than packets with 0. |
| Packet Identifier (PID) | 13 | Identifies the payload’s stream (video, audio, PAT, PMT, …). |
| Transport Scrambling Control (TSC) | 2 | 00 unscrambled, 01 reserved, 10 even key, 11 odd key. |
| Adaptation Field Control | 2 | 00 reserved, 01 payload only, 10 adaptation field only, 11 both. |
| Continuity Counter | 4 | Increments per packet per PID, wraps 15→0; detects drops/reordering. Frozen when Adaptation Field Control is 00 or 10. |
Adaptation Field
Present when Adaptation Field Control is 10 or 11. Variable length, carries timing/misc data.
| Field | Bits | Notes |
|---|
| Adaptation Field Length | 8 | Byte count of everything below this byte. 0 is valid (1-byte stuffing field). |
| Discontinuity Indicator | 1 | 1 = system time base discontinuity (seek, stream switch). |
| Random Access Indicator | 1 | 1 = packet enables random access (e.g. carries an I-frame). |
| Elementary Stream Priority Indicator | 1 | 1 = higher-priority payload. |
| PCR Flag | 1 | 1 = PCR field present. |
| OPCR Flag | 1 | 1 = OPCR field present. |
| Splicing Point Flag | 1 | 1 = splice countdown field present. |
| Transport Private Data Flag | 1 | 1 = private data bytes present. |
| Adaptation Field Extension Flag | 1 | 1 = extension present. |
| Optional fields | var | PCR, OPCR, splice countdown, etc. — gated by the flags above. |
| Stuffing bytes | var | 0xFF padding to fill the declared length. |
Optional Fields (Gated by Flags Above)
| Field | Flag | Bits | Notes |
|---|
| PCR | PCR Flag | 48 | 42-bit timestamp packed into 6 bytes — see below. |
| OPCR | OPCR Flag | 48 | Same layout as PCR. |
| Splice Countdown | Splicing Point Flag | 8 | Signed; TS packets remaining until the splice point. |
| Transport Private Data Length | Transport Private Data Flag | 8 | Byte length of the private data that follows. |
| Transport Private Data | Transport Private Data Flag | var | Broadcaster-defined payload. |
| Adaptation Field Extension | Adaptation Field Extension Flag | var | See below. |
PCR / OPCR Layout
A 42-bit value packed into 6 bytes as base + extension:
| Field | Bits | Notes |
|---|
program_clock_reference_base | 33 | Count of a 90 kHz clock. |
| Reserved | 6 | Ignore; typically all 1s. |
program_clock_reference_extension | 9 | Count of a 27 MHz clock, for sub-tick precision. |
PCR (27 MHz) = base * 300 + extension
PCR (seconds) = PCR (27 MHz) / 27_000_000
Adaptation Field Extension
Present when Adaptation Field Extension Flag is 1.
| Field | Bits | Notes |
|---|
| Adaptation Field Extension Length | 8 | Byte count following this byte. |
| Legal Time Window (LTW) Flag | 1 | 1 = LTW fields present. |
| Piecewise Rate Flag | 1 | 1 = piecewise rate field present. |
| Seamless Splice Flag | 1 | 1 = seamless splice fields present. |
| Reserved | 5 | — |
| Field | Flag | Bits | Notes |
|---|
| LTW Valid Flag | LTW Flag | 1 | 1 = legal_time_window_offset is valid. |
| Legal Time Window Offset | LTW Flag | 15 | Used for video buffering verification. |
| Piecewise Rate | Piecewise Rate Flag | 22 (+2 reserved) | Bitrate over a given segment. |
| Splice Type | Seamless Splice Flag | 4 | Splice/bitstream characteristics at the splice point. |
| DTS Next Access Unit | Seamless Splice Flag | 36 | DTS of the first access unit after the splice point. |
