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Reformatting before SliceContent changes
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Explicit floor and ceil instead of truncation of a / b
Add "pixel_" prefix in order to avoid conflict with width/height
in count of elements in the slice raster
Larger SliceContent formatted array size
QuantizationTable() moved to a formatted array

One floor() was removed by committer as it is unneeded
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@JeromeMartinez @michaelni
JeromeMartinez authored and michaelni committed Jun 17, 2016
1 parent c5e8bc1 commit e28bb95
Showing 1 changed file with 36 additions and 28 deletions.
64 changes: 36 additions & 28 deletions ffv1.md
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Expand Up @@ -74,9 +74,7 @@ __-a__ means negation of a.

__a \* b__ means a multiplied by b.

__a / b__ means a divided by b with truncation of the result toward zero.

__a % b__ means remainder of a divided by b.
__a / b__ means a divided by b.

__a & b__ means bit-wise "and" of a and b.

Expand Down Expand Up @@ -125,6 +123,16 @@ __!a__ means boolean logical "not".
__a ? b : c__ if a is true, then b, otherwise c.
--------------- ----------------------------------------------------------------

## Mathematical functions

--------------- ----------------------------------------------------------------
__⌊a⌋__ the largest integer less than or equal to a
--------------- ----------------------------------------------------------------

--------------- ----------------------------------------------------------------
__⌈a⌉__ the smallest integer greater than or equal to a
--------------- ----------------------------------------------------------------

## Order of operation precedence

When order of precedence is not indicated explicitly by use of parentheses, operations are evaluated in the following order (from top to bottom, operations of same precedence being evaluated from left to right). This order of operations is based on the order of operations used in Standard C.
Expand Down Expand Up @@ -153,7 +161,7 @@ __a...b__ means any value starting from a to b, inclusive.

**remaining\_bits\_in\_bitstream( )** means the count of remaining bits after the current position in the bitstream. It is computed from the NumBytes value multiplied by 8 minus the count of bits already read by the bitstream parser.

**byte\_aligned( )** means remaining\_bits\_in\_bitstream( ) % 8 is 0.
**byte\_aligned( )** means remaining\_bits\_in\_bitstream( ) is a multiple of 8.

\pagebreak

Expand Down Expand Up @@ -462,9 +470,9 @@ The same context which is initialized to 128 is used for all fields in the heade
The following MUST be provided by external means during initialization of the decoder:
**frame\_width** is defined as frame width in pixels.
**frame\_pixel\_width** is defined as frame width in pixels.
**frame\_height** is defined as frame height in pixels.
**frame\_pixel\_height** is defined as frame height in pixels.
Default values at the decoder initialization phase:
Expand Down Expand Up @@ -618,18 +626,18 @@ Inferred to be 0 if not present.

## Slice Content

| |
|------------------------------------------------------------|:------|
|SliceContent( ) { | type |
|    if( colorspace\_type == 0) { | |
|        for( p = 0; p \< primary\_color\_count; p++ ) { | |
|            Plane( p ) | |
|    } else if( colorspace\_type == 1 ) { | |
|        for( y = 0; y \< height; y++ ) | |
|            for( p = 0; p \< primary\_color\_count; p++ ) { | |
|                Line( p, y ) | |
|    } | |
|} | |
| |
|--------------------------------------------------------------|:------|
|SliceContent( ) { | type |
|    if( colorspace\_type == 0) { | |
|        for( p = 0; p \< primary\_color\_count; p++ ) { | |
|            Plane( p ) | |
|    } else if( colorspace\_type == 1 ) { | |
|        for( y = 0; y \< height; y++ ) | |
|            for( p = 0; p \< primary\_color\_count; p++ ) { | |
|                Line( p, y ) | |
|    } | |
|} | |

**primary\_color\_count** is defined as 1 + ( chroma_planes ? 2 : 0 ) + ( alpha_plane ? 1 : 0 ).

Expand Down Expand Up @@ -837,15 +845,15 @@ Table: 0 0 1 1 1 1 2 2-2-2-2-1-1-1-1 0

Stored values: 1, 3, 1

```c
QuantizationTable( i ) { // type
scale = 1
for( j = 0; j < MAX_CONTEXT_INPUTS; j++ ) {
QuantizationTablePerContext( i, j, scale )
scale *= 2 * len_count[ i ][ j ] - 1
}
context_count[ i ] = ( scale + 1 ) / 2
```
| |
|---------------------------------------------------------------------------|
| QuantizationTable( i ) { |
|   scale = 1 |
|   for( j = 0; j < MAX_CONTEXT_INPUTS; j++ ) { |
|       QuantizationTablePerContext( i, j, scale ) |
|       scale \*= 2 \* len_count[ i ][ j ] - 1 |
|   } |
|   context_count[ i ] = ( scale + 1 ) / 2 |


MAX\_CONTEXT\_INPUTS is 5.
Expand Down Expand Up @@ -875,7 +883,7 @@ MAX\_CONTEXT\_INPUTS is 5.

### Restrictions

To ensure that fast multithreaded decoding is possible, starting version 3 and if frame\_width * frame\_height is more than 101376, slice\_width * slice\_height MUST be less or equal to num\_h\_slices * num\_v\_slices / 4.
To ensure that fast multithreaded decoding is possible, starting version 3 and if frame\_pixel\_width * frame\_pixel\_height is more than 101376, slice\_width * slice\_height MUST be less or equal to num\_h\_slices * num\_v\_slices / 4.
Note: 101376 is the frame size in pixels of a 352x288 frame also known as CIF ("Common Intermediate Format") frame size format.

For each frame, each position in the slice raster MUST be filled by one and only one slice of the frame (no missing slice position, no slice overlapping).
Expand Down

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