[FFmpeg-devel] [PATCH] libavcodec/exr.c : A new exr lossy compression technique B44 is added

[greeshma]

The patch is made and FATE tests are done.It accepted, will submit with the
copyrights  and signature.The code is written based on openEXR algorithm of
B44 lossy compression and modified according to the FFmpeg code.


>From 9670e283f38b71c06457c976f3f2040c8d38bbd9 Mon Sep 17 00:00:00 2001
From: greeshmab <greeshmabalabadra at gmail.com>
Date: Tue, 24 Mar 2015 12:36:21 +0530
Subject: [PATCH] A new exr lossy compression technique B44 is added

---
 libavcodec/exr.c | 121
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 6251fb7..b7114be 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -770,6 +770,124 @@ static int piz_uncompress(EXRContext *s, const
uint8_t *src, int ssize,
     return 0;
 }

+
+static void B44_unpack14 ( GetByteContext *gb, uint16_t out[16]){
+    uint16_t shift;
+    const uint8_t *r = gb->buffer;
+    av_assert0(r[2] != 0xfc);
+    out[0] = (r[0] << 8) | r[1];
+    shift = (r[2] >> 2);
+    out[ 1] = out[ 0] + ((r[ 5] >> 2) << shift);
+    out[ 2] = out[ 1] + ((r[ 8] >> 2) << shift);
+    out[ 3] = out[ 2] + ((r[11] >> 2) << shift);
+    out[ 4] = out[ 0] + (((r[ 2] << 4) | (r[ 3] >> 4)) << shift);
+    out[ 5] = out[ 4] + (((r[ 5] << 4) | (r[ 6] >> 4)) << shift);
+    out[ 6] = out[ 5] + (((r[ 8] << 4) | (r[ 9] >> 4)) << shift);
+    out[ 7] = out[ 6] + (((r[11] << 4) | (r[12] >> 4)) << shift);
+    out[ 8] = out[ 4] + (((r[ 3] << 2) | (r[ 4] >> 6)) << shift);
+    out[ 9] = out[ 8] + (((r[ 6] << 2) | (r[ 7] >> 6)) << shift);
+    out[10] = out[ 9] + (((r[ 9] << 2) | (r[10] >> 6)) << shift);
+    out[11] = out[10] + (((r[12] << 2) | (r[13] >> 6)) << shift);
+    out[12] = out[ 8] + (r[ 4]  << shift);
+    out[13] = out[12] + (r[ 7]  << shift);
+    out[14] = out[13] + (r[10]  << shift);
+    out[15] = out[14] + (r[13]  << shift);
+    for (int i = 0; i < 16; ++i) {              //if any out value exceeds
16bits
+        if (out[i] & 0x8000)
+            out[i] &= 0x7fff;
+        else
+            out[i] = ~out[i];
+    }
+}
+
+
+static void B44_unpack3 ( GetByteContext *gb, uint16_t out[16]){
+    const uint8_t *r = gb->buffer;
//pixels have the same value
+    av_assert0(r[2] == 0xfc);
+    out[0] = (r[0] << 8) | r[1];
+    if (out[0] & 0x8000)
+        out[0] &= 0x7fff;
+    else
+        out[0] = ~out[0];
+    for (int i = 1; i < 16; ++i)
+        out[i] = out[0];
+}
+
+
+
+static int b44_uncompress(EXRContext *s, const uint8_t *src,int ssize, int
dsize, EXRThreadData *td)
+
+{
+    GetByteContext gb;
+    unsigned long  dest_len = dsize;
+    uint8_t *out;
+    int i, j;
+    uint16_t *tmp = (uint16_t *)td->tmp;
+    out = td->uncompressed_data;
+    bytestream2_init(&gb, src, ssize);
+    if (uncompress(td->tmp, &dest_len, src, ssize) != Z_OK || dest_len !=
dsize)
+        return AVERROR_INVALIDDATA;
+    for (i = 0; i < s->nb_channels; i++) {
+        EXRChannel *channel = &s->channels[i];
+        int size = channel->pixel_type;
+        int inSize = ssize;
+        if (channel->pixel_type != EXR_HALF) {              // UINT or
FLOAT channel.
+            int n = s->xdelta * s->ydelta * size * sizeof (*tmp);
+            memcpy (tmp, gb.buffer, n);
+            gb.buffer += n;
+            inSize -= n;
+            continue;
+        } else {                                            //EXR_HALF
Channel
+            for (int y=0; y < s->ydelta; y +=4 ) {
+                uint16_t *row0 = tmp + y * s->xdelta;
+                uint16_t *row1 = row0 + s->xdelta;
+                uint16_t *row2 = row1 + s->xdelta;
+                uint16_t *row3 = row2 + s->xdelta;
+                for (int x = 0; x < s->xdelta; x += 4) {
+                    uint16_t out[16];
+                    int num = (x + 3 < s->xdelta)? 4 * sizeof (*out) :
(s->xdelta - x) * sizeof (*out);
+                    if (gb.buffer[2] == 0xfc) {
+                        B44_unpack3 (&gb, out);
+                        gb.buffer += 3;
+                        inSize -= 3;
+                    } else {
+                        B44_unpack14 (&gb, out);
+                        gb.buffer += 14;
+                        inSize -= 14;
+                    }
+                    if (y + 3 < s->ydelta) {
+                        memcpy (row0, &out[ 0], num);
+                        memcpy (row1, &out[ 4], num);
+                        memcpy (row2, &out[ 8], num);
+                        memcpy (row3, &out[12], num);
+                    } else {
+                        memcpy (row0, &out[ 0], num);
+                        if (y + 1 < s->ydelta)
+                            memcpy (row1, &out[ 4], num);
+                        if (y + 2 < s->ydelta)
+                            memcpy (row2, &out[ 8], num);
+                    }
+                    row0 += 4;
+                    row1 += 4;
+                    row2 += 4;
+                    row3 += 4;
+                }
+            }
+        }
+    }
+    for (i = 0; i < s->ysize; i++) {
+        for (j = 0; j < s->nb_channels; j++) {
+            uint16_t *in = tmp + j * s->xdelta * s->ysize + i * s->xdelta;
+            memcpy(out, in, s->xdelta * 2);
+            out += s->xdelta * 2;
+        }
+    }
+    return 0;
+}
+
+
+
 static int pxr24_uncompress(EXRContext *s, const uint8_t *src,
                             int compressed_size, int uncompressed_size,
                             EXRThreadData *td)
@@ -888,6 +1006,8 @@ static int decode_block(AVCodecContext *avctx, void
*tdata,
             break;
         case EXR_RLE:
             ret = rle_uncompress(src, data_size, uncompressed_size, td);
+        case EXR_B44:
+            ret = b44_uncompress(s, src, data_size, uncompressed_size, td);
         }
         if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "decode_block() failed.\n");
@@ -1282,6 +1402,7 @@ static int decode_frame(AVCodecContext *avctx, void
*data,
         s->scan_lines_per_block = 16;
         break;
     case EXR_PIZ:
+    case EXR_B44:
         s->scan_lines_per_block = 32;
         break;
     default:
-- 
2.1.4



Greeshma