Video Compression

VideoNerd

The python script PcrAnalysis.py  is tailored to check PCR integrity (or timing integrity) of MPEG TS stream.

This script analyzes:

  1. whether PCR interval is smaller or equal to 100ms (as required by MPEG System standard). If not a violation is reported.
  2. whether PCR values are monotonic unless the discontinuity flag is set. If not a violation is reported.
  3. whether PCR is coupled with PES header (or aligned to video frame)

Usage:

python PcrAnalysis.py  ts-file

 

Example:

python PcrAnalysis.py  test.ts

Total Pkts  117138, pcr cnt  12296

Maximal PCR Diff 691598 (25.6147ms), attained at packet  309

PCR is not always followed by PES header, dangling pcr cnt  10776

 

 

Elaboration:

‘pcr cnt’ is the total number of PCRs detected in the input stream

‘PCR Diff’ – is measured in units of 27Mhz

‘Dangling pcr cnt’ – PCRs which are not alighned to PES headers

 

 

Note:

PCRs are timestamps in units of 27Mhz which must be transmitted in transport stream at intervals <100ms (mandatory in MPEG2-System).

PCRs are necessary to eliminate clock drift between Sender  and Receiver (the client), otherwise potentially the clock drift can cause Receiver to discard frames because theirs signaled timestamps are smaller Receiver current clock (in such case Receiver would derive that this frames arrive too late).

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