tiles are decoded in parallel within a single frame

Change-Id: I7aca87cb1c239b74eceef72bdc9f672faebac373

factorizes the code in decode_tiles(). reading the offsets backwards
wasn't doing anything to prove tile independence

Change-Id: I0395d3c77205852ebdc55efedc68291e93cef85c

Change-Id: I56f8c50ac382202f66040cd9cfaa05d889572fc7

Change-Id: Idc03f3fca4bf2d0afd33631ea1d3caf8fc34ec29

Warning was: "implicit conversion from enumeration type 'VPX_SCALING_MODE'
(aka 'enum vpx_scaling_mode_1d') to different enumeration type
'VPX_SCALING'".

Change-Id: I45689e439a8775bc1e7534d0ea1ff7c729f2c7f5

Fix warning with -Wstrict-aliasing=1

Change-Id: Ibf4af991f2c82b8ccbdc20362da64be669564333

Wrong value was used in get_tx_type_4x4() function, so making
initialization before that call.

Change-Id: Ief30bb1e0c03b2f23d993bbf9ae18d7150ba9a83

"keyframe" variable in the current code actually means that previous
frame is a keyframe because cm->frame_type has not been initialized
in read_uncompressed_header.

Change-Id: I5645b0816c70abdef5dfc70113018d06276dac77

The clamp operation may not affect the values of the final assigned mv
where compiler may make use of strict aliasing rule to optimize out the
clamp operation. This change made the code segments to better comply
the strict aliasing rule.

Change-Id: I24502ff18bd4f9e62507a879cc8760a91a0fd07e

Added comments to make the codebase build cleanly in Doxygen.

Change-Id: I01e000ceac57dbafa04342858c8f1be250ba20d1

group error checking at the top followed by allocations, setup then
decode.

Change-Id: I877d21326bb767885520511ecea70e5fd1e28054

Change-Id: I5b17f40e515c4bcf9ebef5380270a214af4e0115

When building with new versions of Clang we encounter some issues. Work
around them by adding -fno-strict-aliasing when we detect Clang.

https://code.google.com/p/webm/issues/detail?id=603

Change-Id: I8e945a18a7215bcc627e7a1ee110078413259cc7

Making partition read/write logic more clear.

Change-Id: I1981e90327257d37095567c62d72a103cda1da33

Passing scan & iscan as parameters, adding useful local variables.

Change-Id: Ia2a87906941db9557350d273669ce5c3cdb7235d

replaces use of cur_tile_mi_(row|col)_(start|end) by VP9_COMMON, making
it less stateful and more reusable for parallel tile decoding

Change-Id: I1df09382b4567a0e5f4434825d47c79afe2399be

replace VP9D_COMP usage with the (slightly) more targeted
VP9_COMMON/MACROBLCKD structures.

Change-Id: Ifdd9034f44d69eb94e232dd03c922de763b96a30

* changes:
  vp9: remove partition+entropy contexts from common
  vp9: add above/left_context to MACROBLOCKD
  vp9: add above/left_seg_context to MACROBLOCKD
  vp9: add above/left_context to encoder
  vp9: add above/left_seg_context to encoder
  vp9: pass entropy context directly to set_skip_context
  vp9: pass context directly to partition functions
  vp9/decode: add alloc_tile_storage()

1920x1080

vp90-2-08-tile_1x2_frame_parallel.webm
vp90-2-08-tile_1x2.webm
vp90-2-08-tile_1x4_frame_parallel.webm
vp90-2-08-tile_1x4.webm

vpxenc blue_sky_1080p25.y4m \
  --codec=vp9 -p 2 \
  --frame-parallel=${fpm} \
  --tile-columns=${tc} \
  --limit=10 \
  --auto-alt-ref=1 \
  --lag-in-frames=5 \
  --target-bitrate=2500

Change-Id: Id9c94b722cc553a6865d443a94e8482c78b038bb

these are now handled separately by the encoder and decoder

Change-Id: If9b16f7d734e992fb94a510a6d88f2690d7fb7cb

Change-Id: I75aab21c1692cbad717564cbb436578fddbc348d

Change-Id: I9cbb768c5f857a096cf6c29d6755d0e5e6728435