Propagation delay, Reference, Reference types – Grass Valley Imagestore 750 v.3.0.1 User Manual

Page 38: Features

Features

Reference

Propagation Delay

With the DVE in circuit, the delay through the Imagestore 750 is 2 interlaced fields or 2 progres-
sive frames depending on the video standard. See

DVE (for Program and Preview)

on page 41 for

more information.

Without the DVE in circuit, the delay through the Imagestore 750 can be up to 1 line. The delay
consists of input line’s FIFO depth delay (which depends on the adjustment of the reference
timing) plus a minimum video processing propagation delay.

The video propagation delay for the Imagestore 750 is as follows:

Embedded audio delays are different from those of video. Embedding and de-embedding
circuits are required by SMPTE standards to buffer many samples before processing. The
Imagestore 750’s audio “through-path” propagation delay is measured in audio samples (~20

μs

per audio sample at 48

kHz). Because audio sample duration is significant compared to video

line duration, embedded audio samples present on input video line L will be processed, then
output, on video line L + N, where N is variable and depends on both the video standard and
line L. As a rough guide, N is generally 5 to 12 lines.

Reference

Reference Types

The Imagestore 750 locks to one of the following inputs, in order of priority:

Otherwise the Imagestore 750 will free-run.

Video Standard

Propagation Delay

525i / 59.94

5.4

625i / 50

5.4

1920 × 1080i / 59.94

2.6

1920 × 1080i / 50

2.6

1280 × 720p / 59.94

2.6

1280 × 720p / 50

2.6

Table 4-1: Video Standard Propagation Delay

REF IN

Analog reference input, if present and compatible

PGM IN

If present and at the correct video standard