[FFmpeg-devel] [PATCH 1/1] Add support for Ericsson Texture Compression 1 (ETC1)

Devin Heitmueller dheitmueller at kernellabs.com
Wed Feb 22 19:38:38 EET 2017


This patch adds support for encoding/decoding ETC1 compressed
textures.  This includes support for the PKM file format.

Example usage:

./ffmpeg -i input_image.jpg new.pkm
./ffmpeg -i new.pkm foo.jpg

Signed-off-by: Devin Heitmueller <dheitmueller at kernellabs.com>
---
 libavcodec/Makefile     |   2 +
 libavcodec/allcodecs.c  |   1 +
 libavcodec/avcodec.h    |   1 +
 libavcodec/codec_desc.c |   7 +
 libavcodec/etc1.c       | 707 ++++++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/etc1.h       | 114 ++++++++
 libavcodec/etc1dec.c    |  81 ++++++
 libavcodec/etc1enc.c    |  90 ++++++
 libavcodec/utils.c      |   3 +-
 libavformat/img2.c      |   1 +
 libavformat/img2enc.c   |   2 +-
 11 files changed, 1007 insertions(+), 2 deletions(-)
 create mode 100644 libavcodec/etc1.c
 create mode 100644 libavcodec/etc1.h
 create mode 100644 libavcodec/etc1dec.c
 create mode 100644 libavcodec/etc1enc.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index a1ce264..f5eec15 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -280,6 +280,8 @@ OBJS-$(CONFIG_EIGHTSVX_EXP_DECODER)    += 8svx.o
 OBJS-$(CONFIG_EIGHTSVX_FIB_DECODER)    += 8svx.o
 OBJS-$(CONFIG_ESCAPE124_DECODER)       += escape124.o
 OBJS-$(CONFIG_ESCAPE130_DECODER)       += escape130.o
+OBJS-$(CONFIG_ETC1_ENCODER)            += etc1enc.o etc1.o
+OBJS-$(CONFIG_ETC1_DECODER)            += etc1dec.o etc1.o
 OBJS-$(CONFIG_EVRC_DECODER)            += evrcdec.o acelp_vectors.o lsp.o
 OBJS-$(CONFIG_EXR_DECODER)             += exr.o
 OBJS-$(CONFIG_FFV1_DECODER)            += ffv1dec.o ffv1.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index f12a54d..cd3a662 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -184,6 +184,7 @@ void avcodec_register_all(void)
     REGISTER_DECODER(EIGHTSVX_FIB,      eightsvx_fib);
     REGISTER_DECODER(ESCAPE124,         escape124);
     REGISTER_DECODER(ESCAPE130,         escape130);
+    REGISTER_ENCDEC (ETC1,              etc1);
     REGISTER_DECODER(EXR,               exr);
     REGISTER_ENCDEC (FFV1,              ffv1);
     REGISTER_ENCDEC (FFVHUFF,           ffvhuff);
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 5616fb0..bf86210 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -388,6 +388,7 @@ enum AVCodecID {
     AV_CODEC_ID_DXV,
     AV_CODEC_ID_SCREENPRESSO,
     AV_CODEC_ID_RSCC,
+    AV_CODEC_ID_ETC1,
 
     AV_CODEC_ID_Y41P = 0x8000,
     AV_CODEC_ID_AVRP,
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 35846c0..de7695d 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -1199,6 +1199,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
     },
 
     {
+        .id        = AV_CODEC_ID_ETC1,
+        .type      = AVMEDIA_TYPE_VIDEO,
+        .name      = "etc1",
+        .long_name = NULL_IF_CONFIG_SMALL("ETC1 (Ericsson Texture Compression) image"),
+        .props     = AV_CODEC_PROP_LOSSY,
+    },
+    {
         .id        = AV_CODEC_ID_G2M,
         .type      = AVMEDIA_TYPE_VIDEO,
         .name      = "g2m",
diff --git a/libavcodec/etc1.c b/libavcodec/etc1.c
new file mode 100644
index 0000000..e28d83c
--- /dev/null
+++ b/libavcodec/etc1.c
@@ -0,0 +1,707 @@
+// Copyright 2009 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+// This is a fork of the AOSP project ETC1 codec. The original code can be found
+// at the following web site:
+// https://android.googlesource.com/platform/frameworks/native/+/master/opengl/include/ETC1/
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+#include "etc1.h"
+
+//#include <cstring>
+#include <string.h>
+
+/* From http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt
+
+ The number of bits that represent a 4x4 texel block is 64 bits if
+ <internalformat> is given by ETC1_RGB8_OES.
+
+ The data for a block is a number of bytes,
+
+ {q0, q1, q2, q3, q4, q5, q6, q7}
+
+ where byte q0 is located at the lowest memory address and q7 at
+ the highest. The 64 bits specifying the block is then represented
+ by the following 64 bit integer:
+
+ int64bit = 256*(256*(256*(256*(256*(256*(256*q0+q1)+q2)+q3)+q4)+q5)+q6)+q7;
+
+ ETC1_RGB8_OES:
+
+ a) bit layout in bits 63 through 32 if diffbit = 0
+
+ 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48
+ -----------------------------------------------
+ | base col1 | base col2 | base col1 | base col2 |
+ | R1 (4bits)| R2 (4bits)| G1 (4bits)| G2 (4bits)|
+ -----------------------------------------------
+
+ 47 46 45 44 43 42 41 40 39 38 37 36 35 34  33  32
+ ---------------------------------------------------
+ | base col1 | base col2 | table  | table  |diff|flip|
+ | B1 (4bits)| B2 (4bits)| cw 1   | cw 2   |bit |bit |
+ ---------------------------------------------------
+
+
+ b) bit layout in bits 63 through 32 if diffbit = 1
+
+ 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48
+ -----------------------------------------------
+ | base col1    | dcol 2 | base col1    | dcol 2 |
+ | R1' (5 bits) | dR2    | G1' (5 bits) | dG2    |
+ -----------------------------------------------
+
+ 47 46 45 44 43 42 41 40 39 38 37 36 35 34  33  32
+ ---------------------------------------------------
+ | base col 1   | dcol 2 | table  | table  |diff|flip|
+ | B1' (5 bits) | dB2    | cw 1   | cw 2   |bit |bit |
+ ---------------------------------------------------
+
+
+ c) bit layout in bits 31 through 0 (in both cases)
+
+ 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
+ -----------------------------------------------
+ |       most significant pixel index bits       |
+ | p| o| n| m| l| k| j| i| h| g| f| e| d| c| b| a|
+ -----------------------------------------------
+
+ 15 14 13 12 11 10  9  8  7  6  5  4  3   2   1  0
+ --------------------------------------------------
+ |         least significant pixel index bits       |
+ | p| o| n| m| l| k| j| i| h| g| f| e| d| c | b | a |
+ --------------------------------------------------
+
+
+ Add table 3.17.2: Intensity modifier sets for ETC1 compressed textures:
+
+ table codeword                modifier table
+ ------------------        ----------------------
+ 0                     -8  -2  2   8
+ 1                    -17  -5  5  17
+ 2                    -29  -9  9  29
+ 3                    -42 -13 13  42
+ 4                    -60 -18 18  60
+ 5                    -80 -24 24  80
+ 6                   -106 -33 33 106
+ 7                   -183 -47 47 183
+
+
+ Add table 3.17.3 Mapping from pixel index values to modifier values for
+ ETC1 compressed textures:
+
+ pixel index value
+ ---------------
+ msb     lsb           resulting modifier value
+ -----   -----          -------------------------
+ 1       1            -b (large negative value)
+ 1       0            -a (small negative value)
+ 0       0             a (small positive value)
+ 0       1             b (large positive value)
+
+
+ */
+
+static const int kModifierTable[] = {
+/* 0 */2, 8, -2, -8,
+/* 1 */5, 17, -5, -17,
+/* 2 */9, 29, -9, -29,
+/* 3 */13, 42, -13, -42,
+/* 4 */18, 60, -18, -60,
+/* 5 */24, 80, -24, -80,
+/* 6 */33, 106, -33, -106,
+/* 7 */47, 183, -47, -183 };
+
+static const int kLookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
+
+static inline etc1_byte clamp(int x) {
+    return (etc1_byte) (x >= 0 ? (x < 255 ? x : 255) : 0);
+}
+
+static
+inline int convert4To8(int b) {
+    int c = b & 0xf;
+    return (c << 4) | c;
+}
+
+static
+inline int convert5To8(int b) {
+    int c = b & 0x1f;
+    return (c << 3) | (c >> 2);
+}
+
+static
+inline int convert6To8(int b) {
+    int c = b & 0x3f;
+    return (c << 2) | (c >> 4);
+}
+
+static
+inline int divideBy255(int d) {
+    return (d + 128 + (d >> 8)) >> 8;
+}
+
+static
+inline int convert8To4(int b) {
+    int c = b & 0xff;
+    return divideBy255(c * 15);
+}
+
+static
+inline int convert8To5(int b) {
+    int c = b & 0xff;
+    return divideBy255(c * 31);
+}
+
+static
+inline int convertDiff(int base, int diff) {
+    return convert5To8((0x1f & base) + kLookup[0x7 & diff]);
+}
+
+static
+void decode_subblock(etc1_byte* pOut, int r, int g, int b, const int* table,
+        etc1_uint32 low, int second, int flipped) {
+    int baseX = 0;
+    int baseY = 0;
+    int k;
+    int offset;
+    int delta;
+    etc1_byte *q;
+
+    if (second) {
+        if (flipped) {
+            baseY = 2;
+        } else {
+            baseX = 2;
+        }
+    }
+    for (int i = 0; i < 8; i++) {
+        int x, y;
+        if (flipped) {
+            x = baseX + (i >> 1);
+            y = baseY + (i & 1);
+        } else {
+            x = baseX + (i >> 2);
+            y = baseY + (i & 3);
+        }
+        k = y + (x * 4);
+        offset = ((low >> k) & 1) | ((low >> (k + 15)) & 2);
+        delta = table[offset];
+        q = pOut + 3 * (x + 4 * y);
+        *q++ = clamp(r + delta);
+        *q++ = clamp(g + delta);
+        *q++ = clamp(b + delta);
+    }
+}
+
+// Input is an ETC1 compressed version of the data.
+// Output is a 4 x 4 square of 3-byte pixels in form R, G, B
+
+void etc1_decode_block(const etc1_byte* pIn, etc1_byte* pOut) {
+    etc1_uint32 high = (pIn[0] << 24) | (pIn[1] << 16) | (pIn[2] << 8) | pIn[3];
+    etc1_uint32 low = (pIn[4] << 24) | (pIn[5] << 16) | (pIn[6] << 8) | pIn[7];
+    int tableIndexA;
+    int tableIndexB;
+    const int* tableA;
+    const int* tableB;
+    int flipped;
+    int r1, r2, g1, g2, b1, b2;
+    if (high & 2) {
+        // differential
+        int rBase = high >> 27;
+        int gBase = high >> 19;
+        int bBase = high >> 11;
+        r1 = convert5To8(rBase);
+        r2 = convertDiff(rBase, high >> 24);
+        g1 = convert5To8(gBase);
+        g2 = convertDiff(gBase, high >> 16);
+        b1 = convert5To8(bBase);
+        b2 = convertDiff(bBase, high >> 8);
+    } else {
+        // not differential
+        r1 = convert4To8(high >> 28);
+        r2 = convert4To8(high >> 24);
+        g1 = convert4To8(high >> 20);
+        g2 = convert4To8(high >> 16);
+        b1 = convert4To8(high >> 12);
+        b2 = convert4To8(high >> 8);
+    }
+    tableIndexA = 7 & (high >> 5);
+    tableIndexB = 7 & (high >> 2);
+    tableA = kModifierTable + tableIndexA * 4;
+    tableB = kModifierTable + tableIndexB * 4;
+    flipped = (high & 1) != 0;
+    decode_subblock(pOut, r1, g1, b1, tableA, low, 0, flipped);
+    decode_subblock(pOut, r2, g2, b2, tableB, low, 1, flipped);
+}
+
+typedef struct {
+    etc1_uint32 high;
+    etc1_uint32 low;
+    etc1_uint32 score; // Lower is more accurate
+} etc_compressed;
+
+static
+inline void take_best(etc_compressed* a, const etc_compressed* b) {
+    if (a->score > b->score) {
+        *a = *b;
+    }
+}
+
+static
+void etc_average_colors_subblock(const etc1_byte* pIn, etc1_uint32 inMask,
+        etc1_byte* pColors, int flipped, int second) {
+    int r = 0;
+    int g = 0;
+    int b = 0;
+
+    if (flipped) {
+        int by = 0;
+        if (second) {
+            by = 2;
+        }
+        for (int y = 0; y < 2; y++) {
+            int yy = by + y;
+            for (int x = 0; x < 4; x++) {
+                int i = x + 4 * yy;
+                if (inMask & (1 << i)) {
+                    const etc1_byte* p = pIn + i * 3;
+                    r += *(p++);
+                    g += *(p++);
+                    b += *(p++);
+                }
+            }
+        }
+    } else {
+        int bx = 0;
+        if (second) {
+            bx = 2;
+        }
+        for (int y = 0; y < 4; y++) {
+            for (int x = 0; x < 2; x++) {
+                int xx = bx + x;
+                int i = xx + 4 * y;
+                if (inMask & (1 << i)) {
+                    const etc1_byte* p = pIn + i * 3;
+                    r += *(p++);
+                    g += *(p++);
+                    b += *(p++);
+                }
+            }
+        }
+    }
+    pColors[0] = (etc1_byte)((r + 4) >> 3);
+    pColors[1] = (etc1_byte)((g + 4) >> 3);
+    pColors[2] = (etc1_byte)((b + 4) >> 3);
+}
+
+static
+inline int square(int x) {
+    return x * x;
+}
+
+static etc1_uint32 chooseModifier(const etc1_byte* pBaseColors,
+        const etc1_byte* pIn, etc1_uint32 *pLow, int bitIndex,
+        const int* pModifierTable) {
+    etc1_uint32 bestScore = ~0;
+    int bestIndex = 0;
+    int pixelR = pIn[0];
+    int pixelG = pIn[1];
+    int pixelB = pIn[2];
+    int r = pBaseColors[0];
+    int g = pBaseColors[1];
+    int b = pBaseColors[2];
+    etc1_uint32 lowMask;
+    for (int i = 0; i < 4; i++) {
+        int modifier = pModifierTable[i];
+	int decodedR, decodedG, decodedB;
+        etc1_uint32 score;
+        decodedG = clamp(g + modifier);
+        score = (etc1_uint32) (6 * square(decodedG - pixelG));
+        if (score >= bestScore) {
+            continue;
+        }
+        decodedR = clamp(r + modifier);
+        score += (etc1_uint32) (3 * square(decodedR - pixelR));
+        if (score >= bestScore) {
+            continue;
+        }
+        decodedB = clamp(b + modifier);
+        score += (etc1_uint32) square(decodedB - pixelB);
+        if (score < bestScore) {
+            bestScore = score;
+            bestIndex = i;
+        }
+    }
+    lowMask = (((bestIndex >> 1) << 16) | (bestIndex & 1))
+            << bitIndex;
+    *pLow |= lowMask;
+    return bestScore;
+}
+
+static
+void etc_encode_subblock_helper(const etc1_byte* pIn, etc1_uint32 inMask,
+        etc_compressed* pCompressed, int flipped, int second,
+        const etc1_byte* pBaseColors, const int* pModifierTable) {
+    int score = pCompressed->score;
+    if (flipped) {
+        int by = 0;
+        if (second) {
+            by = 2;
+        }
+        for (int y = 0; y < 2; y++) {
+            int yy = by + y;
+            for (int x = 0; x < 4; x++) {
+                int i = x + 4 * yy;
+                if (inMask & (1 << i)) {
+                    score += chooseModifier(pBaseColors, pIn + i * 3,
+                            &pCompressed->low, yy + x * 4, pModifierTable);
+                }
+            }
+        }
+    } else {
+        int bx = 0;
+        if (second) {
+            bx = 2;
+        }
+        for (int y = 0; y < 4; y++) {
+            for (int x = 0; x < 2; x++) {
+                int xx = bx + x;
+                int i = xx + 4 * y;
+                if (inMask & (1 << i)) {
+                    score += chooseModifier(pBaseColors, pIn + i * 3,
+                            &pCompressed->low, y + xx * 4, pModifierTable);
+                }
+            }
+        }
+    }
+    pCompressed->score = score;
+}
+
+static int inRange4bitSigned(int color) {
+    return color >= -4 && color <= 3;
+}
+
+static void etc_encodeBaseColors(etc1_byte* pBaseColors,
+        const etc1_byte* pColors, etc_compressed* pCompressed) {
+    int r1, g1, b1, r2, g2, b2; // 8 bit base colors for sub-blocks
+    int differential;
+    {
+        int r51 = convert8To5(pColors[0]);
+        int g51 = convert8To5(pColors[1]);
+        int b51 = convert8To5(pColors[2]);
+        int r52 = convert8To5(pColors[3]);
+        int g52 = convert8To5(pColors[4]);
+        int b52 = convert8To5(pColors[5]);
+        int dr, dg, db;
+
+        r1 = convert5To8(r51);
+        g1 = convert5To8(g51);
+        b1 = convert5To8(b51);
+
+        dr = r52 - r51;
+        dg = g52 - g51;
+        db = b52 - b51;
+
+        differential = inRange4bitSigned(dr) && inRange4bitSigned(dg)
+                && inRange4bitSigned(db);
+        if (differential) {
+            r2 = convert5To8(r51 + dr);
+            g2 = convert5To8(g51 + dg);
+            b2 = convert5To8(b51 + db);
+            pCompressed->high |= (r51 << 27) | ((7 & dr) << 24) | (g51 << 19)
+                    | ((7 & dg) << 16) | (b51 << 11) | ((7 & db) << 8) | 2;
+        }
+    }
+
+    if (!differential) {
+        int r41 = convert8To4(pColors[0]);
+        int g41 = convert8To4(pColors[1]);
+        int b41 = convert8To4(pColors[2]);
+        int r42 = convert8To4(pColors[3]);
+        int g42 = convert8To4(pColors[4]);
+        int b42 = convert8To4(pColors[5]);
+        r1 = convert4To8(r41);
+        g1 = convert4To8(g41);
+        b1 = convert4To8(b41);
+        r2 = convert4To8(r42);
+        g2 = convert4To8(g42);
+        b2 = convert4To8(b42);
+        pCompressed->high |= (r41 << 28) | (r42 << 24) | (g41 << 20) | (g42
+                << 16) | (b41 << 12) | (b42 << 8);
+    }
+    pBaseColors[0] = r1;
+    pBaseColors[1] = g1;
+    pBaseColors[2] = b1;
+    pBaseColors[3] = r2;
+    pBaseColors[4] = g2;
+    pBaseColors[5] = b2;
+}
+
+static
+void etc_encode_block_helper(const etc1_byte* pIn, etc1_uint32 inMask,
+        const etc1_byte* pColors, etc_compressed* pCompressed, int flipped) {
+    etc1_byte pBaseColors[6];
+    int originalHigh;
+    const int* pModifierTable;
+    etc_compressed firstHalf;
+
+    pCompressed->score = ~0;
+    pCompressed->high = (flipped ? 1 : 0);
+    pCompressed->low = 0;
+
+    etc_encodeBaseColors(pBaseColors, pColors, pCompressed);
+
+    originalHigh = pCompressed->high;
+
+    pModifierTable = kModifierTable;
+    for (int i = 0; i < 8; i++, pModifierTable += 4) {
+        etc_compressed temp;
+        temp.score = 0;
+        temp.high = originalHigh | (i << 5);
+        temp.low = 0;
+        etc_encode_subblock_helper(pIn, inMask, &temp, flipped, 0,
+                pBaseColors, pModifierTable);
+        take_best(pCompressed, &temp);
+    }
+    pModifierTable = kModifierTable;
+    firstHalf = *pCompressed;
+    for (int i = 0; i < 8; i++, pModifierTable += 4) {
+        etc_compressed temp;
+        temp.score = firstHalf.score;
+        temp.high = firstHalf.high | (i << 2);
+        temp.low = firstHalf.low;
+        etc_encode_subblock_helper(pIn, inMask, &temp, flipped, 1,
+                pBaseColors + 3, pModifierTable);
+        if (i == 0) {
+            *pCompressed = temp;
+        } else {
+            take_best(pCompressed, &temp);
+        }
+    }
+}
+
+static void writeBigEndian(etc1_byte* pOut, etc1_uint32 d) {
+    pOut[0] = (etc1_byte)(d >> 24);
+    pOut[1] = (etc1_byte)(d >> 16);
+    pOut[2] = (etc1_byte)(d >> 8);
+    pOut[3] = (etc1_byte) d;
+}
+
+// Input is a 4 x 4 square of 3-byte pixels in form R, G, B
+// inmask is a 16-bit mask where bit (1 << (x + y * 4)) tells whether the corresponding (x,y)
+// pixel is valid or not. Invalid pixel color values are ignored when compressing.
+// Output is an ETC1 compressed version of the data.
+
+void etc1_encode_block(const etc1_byte* pIn, etc1_uint32 inMask,
+        etc1_byte* pOut) {
+    etc1_byte colors[6];
+    etc1_byte flippedColors[6];
+    etc_compressed a, b;
+    etc_average_colors_subblock(pIn, inMask, colors, 0, 0);
+    etc_average_colors_subblock(pIn, inMask, colors + 3, 0, 1);
+    etc_average_colors_subblock(pIn, inMask, flippedColors, 1, 0);
+    etc_average_colors_subblock(pIn, inMask, flippedColors + 3, 1, 1);
+
+    etc_encode_block_helper(pIn, inMask, colors, &a, 0);
+    etc_encode_block_helper(pIn, inMask, flippedColors, &b, 1);
+    take_best(&a, &b);
+    writeBigEndian(pOut, a.high);
+    writeBigEndian(pOut + 4, a.low);
+}
+
+// Return the size of the encoded image data (does not include size of PKM header).
+
+etc1_uint32 etc1_get_encoded_data_size(etc1_uint32 width, etc1_uint32 height) {
+    return (((width + 3) & ~3) * ((height + 3) & ~3)) >> 1;
+}
+
+// Encode an entire image.
+// pIn - pointer to the image data. Formatted such that the Red component of
+//       pixel (x,y) is at pIn + pixelSize * x + stride * y + redOffset;
+// pOut - pointer to encoded data. Must be large enough to store entire encoded image.
+
+int etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride, etc1_byte* pOut) {
+    static const unsigned short kYMask[] = { 0x0, 0xf, 0xff, 0xfff, 0xffff };
+    static const unsigned short kXMask[] = { 0x0, 0x1111, 0x3333, 0x7777,
+            0xffff };
+    etc1_byte block[ETC1_DECODED_BLOCK_SIZE];
+    etc1_byte encoded[ETC1_ENCODED_BLOCK_SIZE];
+    etc1_uint32 encodedWidth = (width + 3) & ~3;
+    etc1_uint32 encodedHeight = (height + 3) & ~3;
+
+    if (pixelSize < 2 || pixelSize > 3) {
+        return -1;
+    }
+
+    for (etc1_uint32 y = 0; y < encodedHeight; y += 4) {
+        etc1_uint32 yEnd = height - y;
+        int ymask;
+        if (yEnd > 4) {
+            yEnd = 4;
+        }
+        ymask = kYMask[yEnd];
+        for (etc1_uint32 x = 0; x < encodedWidth; x += 4) {
+            etc1_uint32 xEnd = width - x;
+            int mask;
+            if (xEnd > 4) {
+                xEnd = 4;
+            }
+            mask = ymask & kXMask[xEnd];
+            for (etc1_uint32 cy = 0; cy < yEnd; cy++) {
+                etc1_byte* q = block + (cy * 4) * 3;
+                const etc1_byte* p = pIn + pixelSize * x + stride * (y + cy);
+                if (pixelSize == 3) {
+                    memcpy(q, p, xEnd * 3);
+                } else {
+                    for (etc1_uint32 cx = 0; cx < xEnd; cx++) {
+                        int pixel = (p[1] << 8) | p[0];
+                        *q++ = convert5To8(pixel >> 11);
+                        *q++ = convert6To8(pixel >> 5);
+                        *q++ = convert5To8(pixel);
+                        p += pixelSize;
+                    }
+                }
+            }
+            etc1_encode_block(block, mask, encoded);
+            memcpy(pOut, encoded, sizeof(encoded));
+            pOut += sizeof(encoded);
+        }
+    }
+    return 0;
+}
+
+// Decode an entire image.
+// pIn - pointer to encoded data.
+// pOut - pointer to the image data. Will be written such that the Red component of
+//       pixel (x,y) is at pIn + pixelSize * x + stride * y + redOffset. Must be
+//        large enough to store entire image.
+
+
+int etc1_decode_image(const etc1_byte* pIn, etc1_byte* pOut,
+        etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride) {
+    etc1_byte block[ETC1_DECODED_BLOCK_SIZE];
+    etc1_uint32 encodedWidth = (width + 3) & ~3;
+    etc1_uint32 encodedHeight = (height + 3) & ~3;
+
+    if (pixelSize < 2 || pixelSize > 3) {
+        return -1;
+    }
+
+    for (etc1_uint32 y = 0; y < encodedHeight; y += 4) {
+        etc1_uint32 yEnd = height - y;
+        if (yEnd > 4) {
+            yEnd = 4;
+        }
+        for (etc1_uint32 x = 0; x < encodedWidth; x += 4) {
+            etc1_uint32 xEnd = width - x;
+            if (xEnd > 4) {
+                xEnd = 4;
+            }
+            etc1_decode_block(pIn, block);
+            pIn += ETC1_ENCODED_BLOCK_SIZE;
+            for (etc1_uint32 cy = 0; cy < yEnd; cy++) {
+                const etc1_byte* q = block + (cy * 4) * 3;
+                etc1_byte* p = pOut + pixelSize * x + stride * (y + cy);
+                if (pixelSize == 3) {
+                    memcpy(p, q, xEnd * 3);
+                } else {
+                    for (etc1_uint32 cx = 0; cx < xEnd; cx++) {
+                        etc1_byte r = *q++;
+                        etc1_byte g = *q++;
+                        etc1_byte b = *q++;
+                        etc1_uint32 pixel = ((r >> 3) << 11) | ((g >> 2) << 5) | (b >> 3);
+                        *p++ = (etc1_byte) pixel;
+                        *p++ = (etc1_byte) (pixel >> 8);
+                    }
+                }
+            }
+        }
+    }
+    return 0;
+}
+
+static const char kMagic[] = { 'P', 'K', 'M', ' ', '1', '0' };
+
+static const etc1_uint32 ETC1_PKM_FORMAT_OFFSET = 6;
+static const etc1_uint32 ETC1_PKM_ENCODED_WIDTH_OFFSET = 8;
+static const etc1_uint32 ETC1_PKM_ENCODED_HEIGHT_OFFSET = 10;
+static const etc1_uint32 ETC1_PKM_WIDTH_OFFSET = 12;
+static const etc1_uint32 ETC1_PKM_HEIGHT_OFFSET = 14;
+
+static const etc1_uint32 ETC1_RGB_NO_MIPMAPS = 0;
+
+static void writeBEUint16(etc1_byte* pOut, etc1_uint32 data) {
+    pOut[0] = (etc1_byte) (data >> 8);
+    pOut[1] = (etc1_byte) data;
+}
+
+static etc1_uint32 readBEUint16(const etc1_byte* pIn) {
+    return (pIn[0] << 8) | pIn[1];
+}
+
+// Format a PKM header
+
+void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height) {
+    etc1_uint32 encodedWidth;
+    etc1_uint32 encodedHeight;
+
+    memcpy(pHeader, kMagic, sizeof(kMagic));
+    encodedWidth = (width + 3) & ~3;
+    encodedHeight = (height + 3) & ~3;
+    writeBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET, ETC1_RGB_NO_MIPMAPS);
+    writeBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET, encodedWidth);
+    writeBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET, encodedHeight);
+    writeBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET, width);
+    writeBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET, height);
+}
+
+// Check if a PKM header is correctly formatted.
+
+etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader) {
+    etc1_uint32 format;
+    etc1_uint32 encodedWidth;
+    etc1_uint32 encodedHeight;
+    etc1_uint32 width;
+    etc1_uint32 height;
+
+    if (memcmp(pHeader, kMagic, sizeof(kMagic))) {
+        return 0;
+    }
+    format = readBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET);
+    encodedWidth = readBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET);
+    encodedHeight = readBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET);
+    width = readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
+    height = readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
+    return format == ETC1_RGB_NO_MIPMAPS &&
+            encodedWidth >= width && encodedWidth - width < 4 &&
+            encodedHeight >= height && encodedHeight - height < 4;
+}
+
+// Read the image width from a PKM header
+
+etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader) {
+    return readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
+}
+
+// Read the image height from a PKM header
+
+etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader){
+    return readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
+}
diff --git a/libavcodec/etc1.h b/libavcodec/etc1.h
new file mode 100644
index 0000000..d66ca9d
--- /dev/null
+++ b/libavcodec/etc1.h
@@ -0,0 +1,114 @@
+// Copyright 2009 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+// This is a fork of the AOSP project ETC1 codec. The original code can be found
+// at the following web site:
+// https://android.googlesource.com/platform/frameworks/native/+/master/opengl/libs/ETC1/
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+#ifndef __etc1_h__
+#define __etc1_h__
+
+#define ETC1_ENCODED_BLOCK_SIZE 8
+#define ETC1_DECODED_BLOCK_SIZE 48
+
+#ifndef ETC1_RGB8_OES
+#define ETC1_RGB8_OES 0x8D64
+#endif
+
+typedef unsigned char etc1_byte;
+typedef int etc1_bool;
+typedef unsigned int etc1_uint32;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Encode a block of pixels.
+//
+// pIn is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
+// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+// value of pixel (x, y).
+//
+// validPixelMask is a 16-bit mask where bit (1 << (x + y * 4)) indicates whether
+// the corresponding (x,y) pixel is valid. Invalid pixel color values are ignored when compressing.
+//
+// pOut is an ETC1 compressed version of the data.
+
+void etc1_encode_block(const etc1_byte* pIn, etc1_uint32 validPixelMask, etc1_byte* pOut);
+
+// Decode a block of pixels.
+//
+// pIn is an ETC1 compressed version of the data.
+//
+// pOut is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
+// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+// value of pixel (x, y).
+
+void etc1_decode_block(const etc1_byte* pIn, etc1_byte* pOut);
+
+// Return the size of the encoded image data (does not include size of PKM header).
+
+etc1_uint32 etc1_get_encoded_data_size(etc1_uint32 width, etc1_uint32 height);
+
+// Encode an entire image.
+// pIn - pointer to the image data. Formatted such that
+//       pixel (x,y) is at pIn + pixelSize * x + stride * y;
+// pOut - pointer to encoded data. Must be large enough to store entire encoded image.
+// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
+// returns non-zero if there is an error.
+
+int etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride, etc1_byte* pOut);
+
+// Decode an entire image.
+// pIn - pointer to encoded data.
+// pOut - pointer to the image data. Will be written such that
+//        pixel (x,y) is at pIn + pixelSize * x + stride * y. Must be
+//        large enough to store entire image.
+// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
+// returns non-zero if there is an error.
+
+int etc1_decode_image(const etc1_byte* pIn, etc1_byte* pOut,
+        etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride);
+
+// Size of a PKM header, in bytes.
+
+#define ETC_PKM_HEADER_SIZE 16
+
+// Format a PKM header
+
+void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height);
+
+// Check if a PKM header is correctly formatted.
+
+etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader);
+
+// Read the image width from a PKM header
+
+etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader);
+
+// Read the image height from a PKM header
+
+etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/libavcodec/etc1dec.c b/libavcodec/etc1dec.c
new file mode 100644
index 0000000..72151cd
--- /dev/null
+++ b/libavcodec/etc1dec.c
@@ -0,0 +1,81 @@
+/*
+ * ETC1 image format
+ * Copyright (c) 2017 Devin Heitmueller <dheitmueller at kernellabs.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "internal.h"
+#include "etc1.h"
+
+static int decode_frame(AVCodecContext *avctx,
+                        void *data, int *got_frame,
+                        AVPacket *avpkt)
+{
+    const uint8_t *buf     = avpkt->data;
+    AVFrame *p             = data;
+    int ret;
+
+    /* check signature */
+    if (avpkt->size < ETC_PKM_HEADER_SIZE) {
+        av_log(avctx, AV_LOG_ERROR, "Not enough data %d\n",
+               avpkt->size);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (etc1_pkm_is_valid(buf) == 0) {
+        av_log(avctx, AV_LOG_ERROR, "PKM header invalid\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    avctx->pix_fmt = AV_PIX_FMT_RGB24;
+    avctx->width  = etc1_pkm_get_width(buf);
+    avctx->height = etc1_pkm_get_height(buf);
+    
+    if (ff_get_buffer(avctx, p, AV_GET_BUFFER_FLAG_REF) < 0) {
+        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
+        goto fail;
+    }
+    
+    p->pict_type        = AV_PICTURE_TYPE_I;
+    p->key_frame        = 1;
+    p->interlaced_frame = 0;
+
+    ret = etc1_decode_image(buf + ETC_PKM_HEADER_SIZE, p->data[0],
+                            avctx->width, avctx->height, 3, p->linesize[0]);
+    if (ret != 0) {
+        av_log(avctx, AV_LOG_ERROR, "ETC1 decode failure: %d\n", ret);
+        return AVERROR_INVALIDDATA;
+    }
+    *got_frame = 1;
+
+the_end:
+    return ret;
+fail:
+    ret = -1;
+    goto the_end;
+}
+
+AVCodec ff_etc1_decoder = {
+    .name           = "etc1",
+    .long_name      = NULL_IF_CONFIG_SMALL("ETC1 (Ericsson Texture Compression) image"),
+    .type           = AVMEDIA_TYPE_VIDEO,
+    .id             = AV_CODEC_ID_ETC1,
+    .decode         = decode_frame,
+    .capabilities   = AV_CODEC_CAP_DR1,
+};
diff --git a/libavcodec/etc1enc.c b/libavcodec/etc1enc.c
new file mode 100644
index 0000000..f40b363
--- /dev/null
+++ b/libavcodec/etc1enc.c
@@ -0,0 +1,90 @@
+/*
+ * ETC1 image format
+ * Copyright (c) 2017 Devin Heitmueller <dheitmueller at kernellabs.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "etc1.h"
+
+static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
+                        const AVFrame *pict, int *got_packet)
+{
+    const AVFrame *const p = pict;
+    int max_packet_size, ret;
+
+    /* ETC1 has a well-defined compressed output size */
+    max_packet_size = etc1_get_encoded_data_size(p->width, p->height) + ETC_PKM_HEADER_SIZE;
+
+    if (!pkt->data &&
+        (ret = av_new_packet(pkt, max_packet_size)) < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Could not allocate output packet of size %d.\n",
+               max_packet_size);
+        return ret;
+    }
+    pkt->size = max_packet_size;
+
+    etc1_pkm_format_header(pkt->data, p->width, p->height);
+
+    /* For the moment only support RGB24 (i.e. pixelsize=3) */
+    ret = etc1_encode_image(p->data[0], p->width, p->height, 3, p->linesize[0],
+			    pkt->data + ETC_PKM_HEADER_SIZE);
+    if (ret != 0) {
+        av_log(avctx, AV_LOG_ERROR, "Encode failure error=%d.\n", ret);
+        goto fail;
+    }
+
+    pkt->flags |= AV_PKT_FLAG_KEY;
+    *got_packet = 1;
+
+the_end:
+    return ret;
+fail:
+    ret = -1;
+    goto the_end;
+}
+
+static av_cold int etc1_enc_init(AVCodecContext *avctx)
+{
+#if FF_API_CODED_FRAME
+FF_DISABLE_DEPRECATION_WARNINGS
+    avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
+    avctx->coded_frame->key_frame = 1;
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
+    return 0;
+}
+
+static const AVClass etc1_class = {
+    .class_name = "etc1",
+    .item_name  = av_default_item_name,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVCodec ff_etc1_encoder = {
+    .name           = "etc1",
+    .long_name      = NULL_IF_CONFIG_SMALL("ETC1 (Ericsson Texture Compression) image"),
+    .type           = AVMEDIA_TYPE_VIDEO,
+    .id             = AV_CODEC_ID_ETC1,
+    .priv_class     = &etc1_class,
+    .init           = etc1_enc_init,
+    .encode2        = encode_frame,
+    .pix_fmts       = (const enum AVPixelFormat[]) {
+        AV_PIX_FMT_RGB24, AV_PIX_FMT_NONE
+    },
+};
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index f4085bf..6bf751d 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -397,7 +397,8 @@ void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
         break;
     case AV_PIX_FMT_BGR24:
         if ((s->codec_id == AV_CODEC_ID_MSZH) ||
-            (s->codec_id == AV_CODEC_ID_ZLIB)) {
+            (s->codec_id == AV_CODEC_ID_ZLIB) ||
+            (s->codec_id == AV_CODEC_ID_ETC1)) {
             w_align = 4;
             h_align = 4;
         }
diff --git a/libavformat/img2.c b/libavformat/img2.c
index f9f53ff..e6e061a 100644
--- a/libavformat/img2.c
+++ b/libavformat/img2.c
@@ -77,6 +77,7 @@ const IdStrMap ff_img_tags[] = {
     { AV_CODEC_ID_XBM,        "xbm"      },
     { AV_CODEC_ID_XFACE,      "xface"    },
     { AV_CODEC_ID_XWD,        "xwd"      },
+    { AV_CODEC_ID_ETC1,       "pkm"      },
     { AV_CODEC_ID_NONE,       NULL       }
 };
 
diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
index 1297b1a..5a254c1 100644
--- a/libavformat/img2enc.c
+++ b/libavformat/img2enc.c
@@ -221,7 +221,7 @@ static const AVClass img2mux_class = {
 AVOutputFormat ff_image2_muxer = {
     .name           = "image2",
     .long_name      = NULL_IF_CONFIG_SMALL("image2 sequence"),
-    .extensions     = "bmp,dpx,jls,jpeg,jpg,ljpg,pam,pbm,pcx,pgm,pgmyuv,png,"
+    .extensions     = "bmp,dpx,jls,jpeg,jpg,ljpg,pam,pbm,pcx,pgm,pgmyuv,png,pkm,"
                       "ppm,sgi,tga,tif,tiff,jp2,j2c,j2k,xwd,sun,ras,rs,im1,im8,im24,"
                       "sunras,xbm,xface,pix,y",
     .priv_data_size = sizeof(VideoMuxData),
-- 
1.9.1



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