VP2615CGGH1R Просмотр технического описания (PDF) - Mitel Networks

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VP2615CGGH1R

H.261 Decoder

Mitel Networks 

(between 2 and 62 with DIN4 as MSB ), which has been

used for this macroblock. If no new value is provided for a

macroblock then the old value is re-used.

Horizontal MV: This input (on DIN4:0 ) represents the horizon-

tal component of the motion vector. It must always be

provided when motion compensated Inter coding is in use.

Vertical MV: This input (On DIN4:0) represents the vertical

component of the the motion vector. It must always be

provided when motion compensated Inter coding is in use.

Sub Blk No: Each macroBlock contains 6 Sub-blocks, num-

bered 1 through 6. The corresponding binary value should

be provided on DIN2:0, before the RLC coefficients of that

Sub-Block appear. If a Sub-Block contains no coefficients,

then its number need not be provided at all, or it can be

immediately followed by the next sub block number with-

out any intermediate coefficient values. Even though zero

valued sub blocks can simply be ignored in this way, a

2048 clock delay between new macroblocks must still be

maintained by the video de-multiplexer.

Zero Run Count: The number of zero valued coefficients

preceding the (non-zero) RLC coefficient is defined by this

input. DIN 6 and 7 are not used, with the value between 0

and 63 defined by DIN5:0.

RLC Coefficient: This input defines the value of the run length

coded coefficient. It will always be a non-zero value

Wait State: This mode should be used on any cycle where no

data is being input at the DIN port. Wait States can be

SUBBLOCK ORDER WITHIN MACROBLOCK

1

2

5

6

3

4

U

V

Y

PIXEL ORDER WITHIN SUBBLOCK

00 01 02 03 04 05 06 07

08 09 10 11 12 13 14 15

16 17 18 0139 20 21 22 23

24 25 26 27 28 29 30 31

32 33 34 35 36 37 38 39

40 41 42 43 44 45 46 47

48 49 50 51 52 53 54 55

56 57 58 59 60 61 62 63

Fig 5 : Ordering of Pixels within MacroBlock

VP2615

SYSCLK

FRMOUT

MBOUT

VPIX

YUV

Pixel 0

Pixel 1

Pixel 2

Pixel 383

Fig 6 : YUV Port Timing

inserted between any other instructions as required.

Any undefined bits in the above descriptions may be made

high or low as desired.

The first information supplied for a macroblock should be

that contained within the Control Decisions byte. Receipt of

this instruction resets the internal cycle counter for that

MacroBlock. Although some Macro Blocks may contain no

data, the VP2615 requires that at least the Control Decisions,

GOB Number and Macro Block Number be supplied by the

de-multiplexer ( in that order ). All other side information, which

is to be provided for a non zero block, must then be supplied

before any sub block data can be accepted. GOB's and

Macroblocks must be supplied in the correct sequence, but

sub blocks within a macroblock can be in any order. The

VP2615 does not need to be explicitly informed that the last

coefficient has been received within a sub-block. It will wait for

a new sub-block number, or a new Macroblock Control Deci-

sion Byte, before processing the previous sub-block since it

then knows that the sub block is complete.

At least 2048 SYSCLK cycles must separate the start of

one Macro Block (identified by receipt of the Control Decisions

byte) from the start of the following Macro Block. There are,

however, no specific restrictions on the timing of Sub-Blocks

within the MacroBlock. The minimum gap between incoming

macroblocks is needed for internal processing and also for the

time to output 384 decoded values at one quarter the SYSCLK

frequency.

The VP2615 contains two complete macro block buffers in

its input circuitry, which swap on the completion of the process-

ing and outputting of the results. Whilst one is used internally

the other can be loaded with a new macroblock. It essentially

is a macroblock processor and produces the decoded outputs

for a macroblock after two macroblock pipeline delays. When

it is no longer supplied with macroblock inputs then the

pipeline stalls and does not flush out. Thus two macroblocks

from a new picture are needed to produce the decoded

outputs from the last two macroblocks in a previous picture.

YUV Output Port

Decoded pixel data is presented at the YUV port in

standard macroblock format at quarter SYSCLK frequency

(6.75MHz max), and in the macroblock order presented at the

input. Since the VP2615 always expects a complete picture's

worth of GOB's and macroblocks ( unless Skip Picture is sent

by the video de-mux ), then it will always produce a complete

5

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