Choosing the right test video

​For the most consistent A/V sync measurements, choose a test video that matches the refresh rate and type of system you are testing.
Where possible, use a progressive test video whose frame rate matches the display refresh rate:
* 50p for a 50 Hz display
* 59.94p for a 59.94 Hz display
* 60p for a 60 Hz display
When the video frame rate matches the display, each video frame can be presented on a corresponding display refresh. This gives the playback system a simple and repeatable timing relationship and avoids unnecessary frame-rate conversion.
If the rates don't match, the player or display must accommodate the difference. For example, playing 50i material on a 60 Hz display involves both deinterlacing and conversion between incompatible timing rates. The resulting presentation cadence can cause individual visual events to move between display refreshes. At 60 Hz, one refresh is approximately 16.7 ms, so this can introduce significant variation into an A/V sync measurement even when the audio timing itself is stable.

What about interlaced systems?
If you're working in an interlaced production or broadcast environment, such as 50i in the UK/Europe or 59.94i in North America, the best test file depends on what you want to measure.
For the most stable measurement stimulus on a modern progressive display, use 50p at 50 Hz or 59.94p at 59.94 Hz. Progressive video avoids deinterlacing and gives the display a straightforward frame-to-refresh relationship.
However, if you want to measure the actual interlaced signal path, use the corresponding interlaced test file. For example, a 50i test signal will include the effects of any interlaced processing and deinterlacing performed by the playback equipment, video processor or display. Those delays are then legitimately part of the system being measured.
So a 50i user shouldn't automatically choose 50p simply because it produces a more stable stimulus. If the purpose of the test is to measure a real 50i broadcast or production chain, then 50i is the correct test signal.

 

The simple rule

Match the test video to the system you're testing.
For the most stable playback measurement, use 50p/50 Hz, 59.94p/59.94 Hz or 60p/60 Hz.

If you're testing an actual 50i or 59.94i signal chain, use the corresponding interlaced test video so that the measurement includes the real interlaced processing and deinterlacing delays.