2.1.1. Image Information Packets
The identifier is in beat 0, the field width minus 1 in beat 1, field height minus 1 in beat 2, and bits per symbol (BPS) minus 1 and color space information in beat 3.
One or more video packets should follow image information packets, which must have an associated end-of-field packet. If no video packets follow an image information packet (which may sometimes occur in some applications), an end-of-field packet must still follow the image information packet, possibly with other metapackets in between.
The metapacket identifier of ‘0’ is in the low 5 bits of beat 0, the other fields contained in the packet are:
- IntlaceNibble
- Count[6:0]
- Width-1 and Height-1
- SubSa
- Cosite
- ColSpace
IntlaceNibble
The interlaced nibble field describes whether the next video packet is interlaced or progressive.
IntlaceNibble[3] | IntlaceNibble [2] | IntlaceNibble [1] | IntlaceNibble [0] | Description | Frame Type |
---|---|---|---|---|---|
1 | 1 | 1 | 1 | Interlaced F1 field, pairing don't care |
Interlaced |
1 | 0 | Interlaced F1 field, pairing don't care |
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0 | 1 | Interlaced F1 field, paired with the F0 field preceding it |
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0 | 0 | Interlaced F1 field, paired with the F0 field following it |
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0 | 1 | 1 | Interlaced F1 field, pairing don't care |
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1 | 0 | Interlaced F1 field, pairing don't care |
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0 | 1 | Interlaced F1 field, paired with the F0 field following it |
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0 | 0 | Interlaced F1 field, paired with the F0 field preceding it |
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0 | 1 | 1 | 1 | Progressive frame, natively progressive | Progressive |
0 | 1 | 1 | 0 | Progressive frame, deinterlacing status unknown |
Progressive |
0 | 1 | Progressive frame, deinterlaced from an f1 field |
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0 | 0 | Progressive frame, deinterlaced from an f0 field |
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0 | 1 | 1 | Progressive frame, natively progressive | ||
1 | 0 | Progressive frame, deinterlacing status unknown |
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0 | 1 | Progressive frame, deinterlaced from an f1 field |
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0 | 0 | Progressive frame, deinterlaced from an f0 field |
Count[6:0]
These 7 bits are a copy of the low 7 bits of a field count field found in the end-of-field packet.
Width-1 and Height-1
The protocol supports video field widths and heights up to 65536 pixels. The values in the fields require you to add 1 to give the width and height. The protocol then supports 65536 (216). The protocol considers zero width or height video fields error conditions, so you need not code for these.
SubSa
These two bits decode to indicate the video field chroma sampling.
SubSa | Vertical chroma sub-sampling | Horizontal chroma sub-sampling | Chroma sub-sampling term |
---|---|---|---|
00 | 2 | 2 | 420 |
01 | 2 | 1 | UNUSED |
10 | 1 | 2 | 422 |
11 | 1 | 1 | 444 |
The MSB of the SubSa field represents the vertical chroma subsampling, with the horizontal represented by the LSB.
Cosite
These two bits encode the cositing of the chroma samples. The cositing is the position of the chroma sample sites with respect to the luma sample sites.
The cositing of chroma may be unknown, in which case set this field to 00 (top and left).
CoSite | Cositing |
---|---|
00 | Top and left |
01 | Top and center |
10 | Center and left |
11 | Center and center |
ColSpace
These 7 bits encode the color space of the video. You may assign custom color spaces to encodings 64-127.
ColSpace | Color space |
---|---|
0 | RGB |
1 | YCbCr |
2 | YCbCrSD |
3 | YCbCrHD |
4 | Mono |
5 | Raw |
6 | RGB565 |
6-63 | Reserved |
64-127 | User-defined color spaces |