GS1672 datasheet(55/116 Pages) SEMTECH

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GS1672 HD/SD-SDI Serializer with Complete SMPTE

Audio & Video Support

Data Sheet

53623 - 6

July 2011

55 of 116

4.7.17 Frame Sequence Detection - HD

The GS1672 detects the frame sequence that describes the sample distribution for

synchronous audio.

The frame sequence is only used in the generation of audio control packets; where the

Audio Frame Number (AFN) field describes the position of the current frame within the

frame sequence.

The GS1672 sets the AFN of the Primary group control packets to zero when the ASXA

host interface bit is set for asynchronous audio. The GS1672 sets the AFN of the Primary

group control packets to zero, unless the AFNA_AUTO host interface bit is set to produce

automatic AFN generation.

The GS1672 sets the AFN of the Secondary group control packets to zero, when the

ASXB host interface bit is set for asynchronous audio. The GS1672 sets the AFN of the

Secondary group control packets to zero, unless the AFNB_AUTO host interface bit is set

to produce automatic AFN generation.

The GS1672 sets the AFN to one when every frame has the same number of samples:

Frame Rate 23.976Hz - Each frame has exactly 2002 samples

Frame Rate 24.000Hz - Each frame has exactly 2000 samples

Frame Rate 25.000Hz - Each frame has exactly 1920 samples

Frame Rate 30.000Hz - Each frame has exactly 1600 samples

Frame Rate 50.000Hz - Each frame has exactly 960 samples

Frame Rate 60.000Hz - Each frame has exactly 800 samples

When the frame rate is 29.97Hz, an even number of samples (8008) are distributed over

five frames in the following sequence:

1602 1601 1602 1601 1602

Table 4-19: GS1672 SD Audio Group 3 Audio Sample Distribution - 625 line

[3]6

[0],[3](2)

([4],[3]11)25

[4],[3](9)

[0],[3](2)

([4],[3]11)24

[4],[3](14)

Samples

925

888

Lines

300

288

Table 4-20: GS1672 SD Audio Group 4 Audio Sample Distribution - 625 line

[3]6

[0],[3](3)

([4],[3]11)25

[4],[3](8)

[0],[3](3)

([4],[3]11)24

[4],[3](13)

Samples

925

888

Lines

300

288

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