ref: 136857475ecbbcc4ae6fd24f8a9a82b5a2610e4a
parent: acff1627b8505f904fbbb787840fb7239f9ff544
author: John Koleszar <jkoleszar@google.com>
date: Wed Oct 6 18:39:16 EDT 2010
Centralize mb skip state calculation This patch moves the scattered updates to the mb skip state (mode_info_context->mbmi.mb_skip_coeff) to vp8_tokenize_mb. Recent changes to the quantizer exposed a bug where if a macroblock could be coded as a skip but isn't, the encoder would run the loopfilter but the decoder wouldn't, causing a reference buffer mismatch. The loopfilter is controlled by a flag called dc_diff. The decoder looks at the number of decoded coefficients when setting this flag. The encoder sets this flag based on the skip state, since any skippable macroblock should be transmitted as a skip. The coefficient optimization pass (vp8_optimize_b()) could change the coefficients such that a block that was not a skip becomes one. The encoder was not updating the skip state in this situation for intra coded blocks. The underlying issue predates it, but this bug was recently triggered by enabling trellis quantization on the Y2 block in commit dcd29e3, and by changing the quantizer range control in commit 305be4e. Change-Id: I5cce5da0dbc2d22f7d79ee48149f01e868a64802