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Streams > Compliance Streams > AV Sync Test Streams
      AV Synchronization Test Streams  

                     Plain Beep-Flash stream                              Talking Head stream                 Talking Head in PIP style with natural video background

Test streams have 0 ms i.e. no inherent delay in the encoded audio and video presentation times. Multiplexed audio and video content in the transport stream are completely made sure that they don’t have any delay introduced from the multiplexer or in encoding process and are completely in sync.

Reliable test streams with perfect AV-sync and NO inherent audio video delays, enabling you to test with confidence.


Network operators and DTT country specific requirements demand decoded AV from a digital multiplex should be presented in synchronization. Typically, audio should be presented to the viewer no more than 20 ms before the video and no more than 40 ms after it when both components are decoded on an ideal decoder at the times indicated by their respective PTSs.

Receivers shall not introduce significant relative delay between the video and any audio component. AV synchronization is more critical in HD transmission as viewer can easily notice any AV-sync delays.

Narlak Technologies provides specialized AV-sync test stream suites with three tester friendly designs for Coarse AV-sync, Fine AV-sync and Prolonged AV-sync testing purposes.

1. Plain Beep and Flash: Test streams with only Beep and flashes at regular time intervals of time. These streams will be helpful to measure AV presentation delay introduced in decoding and post processing of the AV in the receiver very accurately using a standard oscilloscope or light sensitive LED-microphone setup.

2. Talking Head test stream: Test streams with a person talking. These test streams will help to test coarse AV-sync by visual inspection method. AV-sync can be tested at any given point of time.

3. Talking Head with running video background: Test streams have a video sequence with "Talking Head" video embedded in a Picture In Picture (PIP) style on a real life or natural video content. Video sequence has white frames (flash) and corresponding beep tones at regular time intervals. Audio content is only speech from "Talking Head" video and beeps at corresponding white frames.

"Talking Head" PIP video enables coarse AV-sync to be tested by visual inspection at any given point of time. Beep and flash at regular intervals will help to measure the AV-sync delay introduced in the receiver under test accurately using an oscilloscope or a light sensitive LED-microphone set-up. The background natural or real life video content will keep the receiver (encoder/decoder) under test busy (if not under stress!) compared to the static background of talking head only video.
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   Test stream suite specification highlights  
    # Three tester friendly designs to suite your testing purposes
# Beep and flash streams to easily measure the AV-sync delay introduced by the receiver under test
# Streams have no inherent delay between Beep and Flash PTSs
# Streams with ATSC and DVB applicable video and audio codecs
# Uncompressed AV content for encoder validations with up to 4k resolution depending on frame rates
# Special conditions with AV PES packet lengths
# Effect on receivers AV-sync for error conditions
  Test Streams delivery options  



Decoders (Receivers) testing: MPEG-2 TS, DVB-T, DVB-T2, DVB-C, DVB-S and ATSC

Encoders testing: Uncompressed Quicktime YUV 422 10 bit or MS AVI RGB 24 bit upto 4k (4096x2304 px) depending on the frame rates.
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   AV-sync Measurement Hardware  

Narlak Technologies offers a PC based hardware solution with USB interface which can be used along with test streams to measure the AV presentation delay of the analog AV outputs (CVBS, SCART) of a Digital TV receiver.

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