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; Copyright (c) 2011 The Chromium Authors. All rights reserved.
; Use of this source code is governed by a BSD-style license that can be
; found in the LICENSE file.
;
; void SYMBOL(const uint8* argb, uint8* y, uint8* u, uint8* v, int width);
;
; The main code that converts RGB pixels to YUV pixels. This function roughly
; consists of three parts: converting one ARGB pixel to YUV pixels, converting
; two ARGB pixels to YUV pixels, and converting four ARGB pixels to YUV pixels.
; To write the structure of this function in C, it becomes the snippet listed
; below.
;
; if (width & 1) {
; --width;
; // Convert one ARGB pixel to one Y pixel, one U pixel, and one V pixel.
; }
;
; if (width & 2) {
; width -= 2;
; // Convert two ARGB pixels to two Y pixels, one U pixel, and one V pixel.
; }
;
; while (width) {
; width -= 4;
; // Convert four ARGB pixels to four Y pixels, two U pixels, and two V
; // pixels.
; }
;
global mangle(SYMBOL) PRIVATE
align function_align
mangle(SYMBOL):
%assign stack_offset 0
PROLOGUE 5, 6, 8, ARGB, Y, U, V, WIDTH, TEMP
; Initialize constants used in this function. (We use immediates to avoid
; dependency onto GOT.)
LOAD_XMM XMM_CONST_Y0, 0x00420219
LOAD_XMM XMM_CONST_Y1, 0x00007F00
LOAD_XMM XMM_CONST_U, 0x00DAB670
LOAD_XMM XMM_CONST_V, 0x0070A2EE
LOAD_XMM XMM_CONST_128, 0x00800080
.convert_one_pixel:
; Divide the input width by two so it represents the offsets for u[] and v[].
; When the width is odd, We read the rightmost ARGB pixel and convert its
; colorspace to YUV. This code stores one Y pixel, one U pixel, and one V
; pixel.
sar WIDTHq, 1
jnc .convert_two_pixels
; Read one ARGB (or RGB) pixel.
READ_ARGB xmm0, 1
; Calculate y[0] from one RGB pixel read above.
CALC_Y xmm1, xmm0
movd TEMPd, xmm1
mov BYTE [Yq + WIDTHq * 2], TEMPb
; Calculate u[0] from one RGB pixel read above. If this is an odd line, the
; output pixel contains the U value calculated in the previous call. We also
; read this pixel and calculate their average.
INIT_UV TEMPd, Uq, 4
CALC_UV xmm1, xmm0, XMM_CONST_U, TEMPd
movd TEMPd, xmm1
mov BYTE [Uq + WIDTHq], TEMPb
; Calculate v[0] from one RGB pixel. Same as u[0], we read the result of the
; previous call and get their average.
INIT_UV TEMPd, Uq, 4
CALC_UV xmm1, xmm0, XMM_CONST_V, TEMPd
movd TEMPd, xmm1
mov BYTE [Vq + WIDTHq], TEMPb
.convert_two_pixels:
; If the input width is not a multiple of four, read the rightmost two ARGB
; pixels and convert their colorspace to YUV. This code stores two Y pixels,
; one U pixel, and one V pixel.
test WIDTHb, 2 / 2
jz .convert_four_pixels
sub WIDTHb, 2 / 2
; Read two ARGB (or RGB) pixels.
READ_ARGB xmm0, 2
; Calculate r[0] and r[1] from two RGB pixels read above.
CALC_Y xmm1, xmm0
movd TEMPd, xmm1
mov WORD [Yq + WIDTHq * 2], TEMPw
; Skip calculating u and v if the output buffer is NULL.
test Uq, Uq
jz .convert_four_pixels
; Calculate u[0] from two RGB pixels read above. (For details, read the above
; comment in .convert_one_pixel).
INIT_UV TEMPd, Uq, 2
CALC_UV xmm1, xmm0, XMM_CONST_U, TEMPd
movd TEMPd, xmm1
mov BYTE [Uq + WIDTHq], TEMPb
; Calculate v[0] from two RGB pixels read above.
INIT_UV TEMPd, Vq, 2
CALC_UV xmm1, xmm0, XMM_CONST_V, TEMPd
movd TEMPd, xmm1
mov BYTE [Vq + WIDTHq], TEMPb
.convert_four_pixels:
; Read four ARGB pixels and convert their colorspace to YUV. This code stores
; four Y pixels, two U pixels, and two V pixels.
test WIDTHq, WIDTHq
jz .convert_finish
%if PIXELSIZE == 4
; Check if the input buffer is aligned to a 16-byte boundary and use movdqa
; for reading the ARGB pixels.
test ARGBw, 15
jnz .convert_four_pixels_unaligned
.convert_four_pixels_aligned:
sub WIDTHq, 4 / 2
; Read four ARGB pixels. (We can use movdqa here since we have checked if the
; source address is aligned.)
movdqa xmm0, DQWORD [ARGBq + WIDTHq * 4 * 2]
; Calculate y[0], y[1], y[2],and, y[3] from the input ARGB pixels.
CALC_Y xmm1, xmm0
movd DWORD [Yq + WIDTHq * 2], xmm1
%if SUBSAMPLING == 0
; Skip calculating u and v if the output buffer is NULL, which means we are
; converting an odd line. (When we enable subsampling, these buffers must
; contain the u and v values for the previous call, i.e. these variables must
; not be NULL.)
test Uq, Uq
jz .convert_four_pixels_aligned_next
%endif
; Calculate u[0] and u[1] from four ARGB pixels read above.
INIT_UV TEMPd, Uq, 4
CALC_UV xmm1, xmm0, XMM_CONST_U, TEMPd
movd TEMPd, xmm1
mov WORD [Uq + WIDTHq], TEMPw
; Calculate v[0] and v[1] from four ARGB pixels read above.
INIT_UV TEMPd, Vq, 4
CALC_UV xmm1, xmm0, XMM_CONST_V, TEMPd
movd TEMPd, xmm1
mov WORD [Vq + WIDTHq], TEMPw
%if SUBSAMPLING == 0
.convert_four_pixels_aligned_next:
%endif
test WIDTHq, WIDTHq
jnz .convert_four_pixels_aligned
jmp .convert_finish
%endif
.convert_four_pixels_unaligned:
sub WIDTHq, 4 / 2
; Read four ARGB (or RGB) pixels.
READ_ARGB xmm0, 4
; Calculate y[0], y[1], y[2],and, y[3] from the input ARGB pixels.
CALC_Y xmm1, xmm0
movd DWORD [Yq + WIDTHq * 2], xmm1
%if SUBSAMPLING == 0
; Skip calculating u and v if the output buffer is NULL.
test Uq, Uq
jz .convert_four_pixels_unaligned_next
%endif
; Calculate u[0] and u[1] from the input ARGB pixels.
INIT_UV TEMPd, Uq, 4
CALC_UV xmm1, xmm0, XMM_CONST_U, TEMPd
movd TEMPd, xmm1
mov WORD [Uq + WIDTHq], TEMPw
; Calculate v[0] and v[1] from the input ARGB pixels.
INIT_UV TEMPd, Vq, 4
CALC_UV xmm1, xmm0, XMM_CONST_V, TEMPd
movd TEMPd, xmm1
mov WORD [Vq + WIDTHq], TEMPw
%if SUBSAMPLING == 0
.convert_four_pixels_unaligned_next:
%endif
test WIDTHq, WIDTHq
jnz .convert_four_pixels_unaligned
.convert_finish:
; Just exit this function since this is a void function.
RET
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