thirdparty/scummvm
2
0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

GRAPHICS: Improved JPEG decoder performance

Browse source 
Replaced the 2D IDCT by two 1D IDCT (rows, then columns).
JPEG images now decode about twice as fast as they used to.

svn-id: r55794
This commit is contained in:
Bastien Bouclet 2011-02-06 13:43:40 +00:00
parent 9149100629
commit e7a57de38b
2 changed files with 47 additions and 37 deletions
Download patch file Download diff file Expand all files Collapse all files

80
graphics/jpeg.cpp
View file

@ -33,10 +33,6 @@
namespace Graphics { namespace Graphics {
#ifndef M_SQRT2
#define M_SQRT2 1.41421356237309504880 /* sqrt(2) */
#endif /* M_SQRT2 */
// Order used to traverse the quantization tables // Order used to traverse the quantization tables
static const uint8 _zigZagOrder[64] = { static const uint8 _zigZagOrder[64] = {
0, 1, 8, 16, 9, 2, 3, 10, 0, 1, 8, 16, 9, 2, 3, 10,
@ -49,15 +45,18 @@ static const uint8 _zigZagOrder[64] = {
53, 60, 61, 54, 47, 55, 62, 63 53, 60, 61, 54, 47, 55, 62, 63
}; };
static const double _cosine32[32] = { // IDCT table built with :
1.000000000000000, 0.980785280403230, 0.923879532511287, 0.831469612302545, // _idct8x8[x][y] = cos(((2 * x + 1) * y) * (PI / 16.0)) * 0.5;
0.707106781186548, 0.555570233019602, 0.382683432365090, 0.195090322016128, // _idct8x8[x][y] /= sqrt(2.0) if y == 0
0.000000000000000, -0.195090322016128, -0.382683432365090, -0.555570233019602, static const double _idct8x8[8][8] = {
-0.707106781186547, -0.831469612302545, -0.923879532511287, -0.980785280403230, { 0.353553390593274, 0.490392640201615, 0.461939766255643, 0.415734806151273, 0.353553390593274, 0.277785116509801, 0.191341716182545, 0.097545161008064 },
-1.000000000000000, -0.980785280403230, -0.923879532511287, -0.831469612302545, { 0.353553390593274, 0.415734806151273, 0.191341716182545, -0.097545161008064, -0.353553390593274, -0.490392640201615, -0.461939766255643, -0.277785116509801 },
-0.707106781186548, -0.555570233019602, -0.382683432365090, -0.195090322016129, { 0.353553390593274, 0.277785116509801, -0.191341716182545, -0.490392640201615, -0.353553390593274, 0.097545161008064, 0.461939766255643, 0.415734806151273 },
-0.000000000000000, 0.195090322016128, 0.382683432365090, 0.555570233019602, { 0.353553390593274, 0.097545161008064, -0.461939766255643, -0.277785116509801, 0.353553390593274, 0.415734806151273, -0.191341716182545, -0.490392640201615 },
0.707106781186547, 0.831469612302545, 0.923879532511287, 0.980785280403230 { 0.353553390593274, -0.097545161008064, -0.461939766255643, 0.277785116509801, 0.353553390593274, -0.415734806151273, -0.191341716182545, 0.490392640201615 },
{ 0.353553390593274, -0.277785116509801, -0.191341716182545, 0.490392640201615, -0.353553390593273, -0.097545161008064, 0.461939766255643, -0.415734806151273 },
{ 0.353553390593274, -0.415734806151273, 0.191341716182545, 0.097545161008064, -0.353553390593274, 0.490392640201615, -0.461939766255643, 0.277785116509801 },
{ 0.353553390593274, -0.490392640201615, 0.461939766255643, -0.415734806151273, 0.353553390593273, -0.277785116509801, 0.191341716182545, -0.097545161008064 }
}; };
JPEG::JPEG() : JPEG::JPEG() :
@ -507,18 +506,39 @@ bool JPEG::readMCU(uint16 xMCU, uint16 yMCU) {
return ok; return ok;
} }
float JPEG::idct(int x, int y, int weight, int fx, int fy) { void JPEG::idct8x8(float result[64], const int16 dct[64]) {
byte vx_in = ((int32)((2 * x) + 1) * fx) % 32; float tmp[64];
byte vy_in = ((int32)((2 * y) + 1) * fy) % 32;
float ret = (float)weight * _cosine32[vx_in] * _cosine32[vy_in];
if (fx == 0) // Apply 1D IDCT to rows
ret /= (float)M_SQRT2; for (int y = 0; y < 8; y++) {
for (int x = 0; x < 8; x++) {
tmp[y + x * 8] = dct[0] * _idct8x8[x][0]
+ dct[1] * _idct8x8[x][1]
+ dct[2] * _idct8x8[x][2]
+ dct[3] * _idct8x8[x][3]
+ dct[4] * _idct8x8[x][4]
+ dct[5] * _idct8x8[x][5]
+ dct[6] * _idct8x8[x][6]
+ dct[7] * _idct8x8[x][7];
}
if (fy == 0) dct += 8;
ret /= (float)M_SQRT2; }
return ret; // Apply 1D IDCT to columns
for (int x = 0; x < 8; x++) {
const float *u = tmp + x * 8;
for (int y = 0; y < 8; y++) {
result[y * 8 + x] = u[0] * _idct8x8[y][0]
+ u[1] * _idct8x8[y][1]
+ u[2] * _idct8x8[y][2]
+ u[3] * _idct8x8[y][3]
+ u[4] * _idct8x8[y][4]
+ u[5] * _idct8x8[y][5]
+ u[6] * _idct8x8[y][6]
+ u[7] * _idct8x8[y][7];
}
}
} }
bool JPEG::readDataUnit(uint16 x, uint16 y) { bool JPEG::readDataUnit(uint16 x, uint16 y) {
@ -546,23 +566,13 @@ bool JPEG::readDataUnit(uint16 x, uint16 y) {
DCT[_zigZagOrder[i]] = val; DCT[_zigZagOrder[i]] = val;
} }
// Shortcut the IDCT for DC component // Apply the IDCT
float result[64]; float result[64];
for (uint8 i = 0; i < 64; i++) idct8x8(result, DCT);
result[i] = DCT[0] / 2;
// Apply the IDCT (PAG31)
for (int i = 1; i < 64; i++) {
if (DCT[i])
for (int _y = 0; _y < 8; _y++)
for (int _x = 0; _x < 8; _x++)
result[_y * 8 + _x] += idct(_x, _y, DCT[i], i % 8, i / 8);
}
// Level shift to make the values unsigned // Level shift to make the values unsigned
// Divide by 4 is final part of IDCT
for (int i = 0; i < 64; i++) { for (int i = 0; i < 64; i++) {
result[i] = result[i] / 4 + 128; result[i] = result[i] + 128;
if (result[i] < 0) if (result[i] < 0)
result[i] = 0; result[i] = 0;

4
graphics/jpeg.h
View file

@ -118,8 +118,8 @@ private:
uint8 _bitsData; uint8 _bitsData;
uint8 _bitsNumber; uint8 _bitsNumber;
// Discrete Cosine Transformation // Inverse Discrete Cosine Transformation
float idct(int x, int y, int weight, int fx, int fy); void idct8x8(float dst[64], const int16 src[64]);
}; };
} // End of Graphics namespace } // End of Graphics namespace