[Ffmpeg-devel] [RFC] rtjpeg decoding functions

[Reimar Döffinger]

Hi,
the attached patch constains (untested) rtjpeg decoding functions. These
are _not_ in a decoder module, since I do not know of any pure rtjpeg
codec, and nuv must select between different codings on a per-frame
basis.
Any comments or a "testbed" are welcome.

Greetings,
Reimar D?ffinger
-------------- next part --------------
Index: libavcodec/Makefile
===================================================================
RCS file: /cvsroot/ffmpeg/ffmpeg/libavcodec/Makefile,v
retrieving revision 1.226
diff -u -r1.226 Makefile
--- libavcodec/Makefile	15 Jan 2006 00:28:35 -0000	1.226
+++ libavcodec/Makefile	17 Jan 2006 19:54:48 -0000
@@ -18,7 +18,7 @@
       fft.o mdct.o raw.o golomb.o cabac.o\
       dpcm.o adx.o faandct.o parser.o g726.o \
       vp3dsp.o h264idct.o rangecoder.o pnm.o h263.o msmpeg4.o h263dec.o \
-      opt.o
+      opt.o rtjpeg.o
 
 ifeq ($(CONFIG_AASC_DECODER),yes)
     OBJS+= aasc.o
Index: libavcodec/rtjpeg.c
===================================================================
RCS file: libavcodec/rtjpeg.c
diff -N libavcodec/rtjpeg.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ libavcodec/rtjpeg.c	17 Jan 2006 19:54:50 -0000
@@ -0,0 +1,121 @@
+/*
+ * RTJpeg decoding functions
+ * Copyright (c) 2006 Reimar Doeffinger
+ *
+ * This library 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 of the License, or (at your option) any later version.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include "common.h"
+#include "bitstream.h"
+#include "dsputil.h"
+#include "rtjpeg.h"
+
+#define PUT_COEFF(c) \
+    i = scan[coeff--]; \
+    block[i] = c * quant[i];
+
+static inline int get_block(GetBitContext *gb, DCTELEM *block, uint8_t *scan,
+                            uint32_t *quant) {
+    int coeff, i;
+    int8_t ac;
+    uint8_t dc = get_bits(gb, 8);
+
+    // block not coded
+    if (dc == 255)
+       return 0;
+
+    // number of non-zero coefficients
+    coeff = get_bits(gb, 6);
+    memset(&block[coeff + 1], 0, 63 - coeff);
+
+    // 2 bits per coefficient
+    while (coeff) {
+        ac = get_sbits(gb, 2);
+        if (ac == -2)
+            break; // continue with more bits
+        PUT_COEFF(ac);
+    }
+
+    // 4 bits per coefficient
+    align_get_bits_to(gb, 4);
+    while (coeff) {
+        ac = get_sbits(gb, 4);
+        if (ac == -8)
+            break; // continue with more bits
+        PUT_COEFF(ac);
+    }
+
+    // 8 bits per coefficient
+    align_get_bits_to(gb, 8);
+    while (coeff) {
+        ac = get_sbits(gb, 8);
+        PUT_COEFF(ac);
+    }
+
+    PUT_COEFF(dc);
+    return 1;
+}
+
+void rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f,
+                                uint8_t *buf, int buf_size) {
+    GetBitContext gb;
+    int w = c->w / 16, h = c->h / 16;
+    int x, y;
+    void *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0];
+    void *u = f->data[1], *v = f->data[2];
+    init_get_bits(&gb, buf, buf_size * 8);
+    for (y = 0; y < h; y++) {
+        for (x = 0; x < w; x++) {
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(y1, f->linesize[0], c->block);
+            y1 += 8;
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(y1, f->linesize[0], c->block);
+            y1 += 8;
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(y2, f->linesize[0], c->block);
+            y2 += 8;
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(y2, f->linesize[0], c->block);
+            y2 += 8;
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(u, f->linesize[1], c->block);
+            u += 8;
+            if (get_block(&gb, c->block, c->scan, c->lquant))
+                c->dsp->idct_put(u, f->linesize[2], c->block);
+            v += 8;
+        }
+        y1 += 16 * f->linesize[0] - 16 * w;
+        y2 += 16 * f->linesize[0] - 16 * w;
+        u += 8 * f->linesize[1] - 8 * w;
+        v += 8 * f->linesize[2] - 8 * w;
+    }
+}
+
+void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
+                        int width, int height,
+                        uint32_t *lquant, uint32_t *cquant) {
+    int i;
+    c->dsp = dsp;
+    for (i = 0; i < 64; i++) {
+        int z = ff_zigzag_direct[i];
+        int p = c->dsp->idct_permutation[i];
+        z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
+        c->scan[i] = c->dsp->idct_permutation[z];
+        c->lquant[p] = lquant[i];
+        c->cquant[p] = cquant[i];
+    }
+    c->w = width;
+    c->h = height;
+}
Index: libavcodec/rtjpeg.h
===================================================================
RCS file: libavcodec/rtjpeg.h
diff -N libavcodec/rtjpeg.h
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ libavcodec/rtjpeg.h	17 Jan 2006 19:54:50 -0000
@@ -0,0 +1,13 @@
+#ifndef RTJPEG_H
+#define RTJPEG_H
+
+typedef struct {
+    int w, h;
+    DSPContext *dsp;
+    DCTELEM block[64];
+    uint8_t scan[64];
+    uint32_t lquant[64];
+    uint32_t cquant[64];
+} RTJpegContext;
+
+#endif