Khaled Mammou authored Aug 22, 2018 and David Flynn committed Aug 29, 2018

This commit removes the ability to vary quant_step_size on a per-LoD
basis.  This greatly simplifies the codec configuration, especially
when used in conjunction with dist2 derivation.

cfg update:
 - rename quantizationSteps* -> quantizationStep*
 - update quantizationStep* to single values:
   - lossless-geom lossy-attrs:        8, 16, 32, 64, 128, 256 [8bit]
   - lossless-geom nearlossless-attrs: no change
   - lossless-geom lossless-attrs:     no change
   - lossy-geom    lossy-attrs:        8                       [8bit]

 => 16-bit cat3 sequences are have 8-bit qs values multipled by 255

Khaled Mammou authored Aug 22, 2018 and David Flynn committed Aug 29, 2018

This commit replaces the hard coded threshold values with APS signalling.
The default configuration maintains the hard-coded threshold values based
on bitdepth.

This is an editorial change to improve naming clarity: attr_count
represents the number of elements (dimensionality) in an attribute
set rather than the total number of attributes.

Khaled Mammou authored Aug 27, 2018 and David Flynn committed Aug 29, 2018

This commit fixes an error in the hls: dist2 is capable of being a
64-bit value and must not be signalled as 32-bit.

This commit allows the attribute codec to be parametrised by attribute
bitdepth.  The attribute bitdepth is signalled in the attribute's sequence
parameter set description.  The specified bitdepth affects cliping in the
attribute prediction and reconstruction process.

This commit allows individual payloads to be inserted into the decoder
rather than the decoder expecting to decode each payload in a fixed
order.

When an output pointcloud is ready, the decoder will call a user
supplied callback with the conforming output pointcloud.  The user
may choose to rescale this point cloud as necessary.

This commit removes the "lossless" geometry bypass coding mode that simply
skipped coding of geometry and required the decoder to read the geometry
from the source video.  Bypass coding mode is replaced by octree coding.

This commit rewrites the codec high-level syntax:

 - the bitstream is divided into "bricks" (akin to an AVC/HEVC
   slice/tile).

 - sequence, geometry and attribute parameter sets describe the coding
   parameters in use generally and for a specific brick.

 - marshalling the bitstream payloads to a file format is achieved using
   a type-length-value encoding scheme.

Additionally, the triSoup bitstream scale and translation values have
been unified with (replaced by) the octree counterparts.  For
compatibility, existing command line parameters continue to function
as before.

NB: this commit does not incorporate flexibility in the decoding order.
The decoder requires the bitstream to be presented in a fixed order.