[SCM] libav/experimental: Lagarith decoder by Nathan Caldwell, saintdev at gmail
siretart at users.alioth.debian.org
siretart at users.alioth.debian.org
Sun Jun 30 17:21:35 UTC 2013
The following commit has been merged in the experimental branch:
commit d267b339e4dbf8d70455e3163b2d39aff0efe314
Author: Carl Eugen Hoyos <cehoyos at rainbow.studorg.tuwien.ac.at>
Date: Sat Jan 8 21:22:15 2011 +0000
Lagarith decoder by Nathan Caldwell, saintdev at gmail
Originally committed as revision 26270 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/Changelog b/Changelog
index 6a25ade..76f73ff 100644
--- a/Changelog
+++ b/Changelog
@@ -71,6 +71,7 @@ version <next>:
- FFmpeg metadata format muxer and demuxer
- SubRip (srt) subtitle decoder
- floating-point AC-3 encoder added
+- Lagarith decoder
version 0.6:
diff --git a/doc/general.texi b/doc/general.texi
index 2e5c7d7..cbdc679 100644
--- a/doc/general.texi
+++ b/doc/general.texi
@@ -424,6 +424,7 @@ following image formats are supported:
@tab Codec used in Worms games.
@item Kega Game Video (KGV1) @tab @tab X
@tab Kega emulator screen capture codec.
+ at item Lagarith @tab @tab X
@item LCL (LossLess Codec Library) MSZH @tab @tab X
@item LCL (LossLess Codec Library) ZLIB @tab E @tab E
@item LOCO @tab @tab X
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index ee16b91..90f07d6 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -185,6 +185,7 @@ OBJS-$(CONFIG_JPEGLS_DECODER) += jpeglsdec.o jpegls.o \
OBJS-$(CONFIG_JPEGLS_ENCODER) += jpeglsenc.o jpegls.o
OBJS-$(CONFIG_KGV1_DECODER) += kgv1dec.o
OBJS-$(CONFIG_KMVC_DECODER) += kmvc.o
+OBJS-$(CONFIG_LAGARITH_DECODER) += lagarith.o lagarithrac.o
OBJS-$(CONFIG_LJPEG_ENCODER) += ljpegenc.o mjpegenc.o mjpeg.o \
mpegvideo_enc.o motion_est.o \
ratecontrol.o mpeg12data.o \
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 5ba1998..94da5c0 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -128,6 +128,7 @@ void avcodec_register_all(void)
REGISTER_ENCDEC (JPEGLS, jpegls);
REGISTER_DECODER (KGV1, kgv1);
REGISTER_DECODER (KMVC, kmvc);
+ REGISTER_DECODER (LAGARITH, lagarith);
REGISTER_ENCODER (LJPEG, ljpeg);
REGISTER_DECODER (LOCO, loco);
REGISTER_DECODER (MDEC, mdec);
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 2355a6e..601f8ed 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -32,7 +32,7 @@
#include "libavutil/cpu.h"
#define LIBAVCODEC_VERSION_MAJOR 52
-#define LIBAVCODEC_VERSION_MINOR 107
+#define LIBAVCODEC_VERSION_MINOR 108
#define LIBAVCODEC_VERSION_MICRO 0
#define LIBAVCODEC_VERSION_INT AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
@@ -259,6 +259,7 @@ enum CodecID {
CODEC_ID_A64_MULTI5,
CODEC_ID_R10K,
CODEC_ID_MXPEG,
+ CODEC_ID_LAGARITH,
/* various PCM "codecs" */
CODEC_ID_PCM_S16LE= 0x10000,
diff --git a/libavcodec/lagarith.c b/libavcodec/lagarith.c
new file mode 100644
index 0000000..95179df
--- /dev/null
+++ b/libavcodec/lagarith.c
@@ -0,0 +1,518 @@
+/*
+ * Lagarith lossless decoder
+ * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file libavcodec/lagarith.c
+ * Lagarith lossless decoder
+ * @author Nathan Caldwell
+ */
+
+#include "avcodec.h"
+#include "get_bits.h"
+#include "mathops.h"
+#include "dsputil.h"
+#include "lagarithrac.h"
+
+enum LagarithFrameType {
+ FRAME_RAW = 1, /*!< uncompressed */
+ FRAME_U_RGB24 = 2, /*!< unaligned RGB24 */
+ FRAME_ARITH_YUY2 = 3, /*!< arithmetic coded YUY2 */
+ FRAME_ARITH_RGB24 = 4, /*!< arithmetic coded RGB24 */
+ FRAME_SOLID_GRAY = 5, /*!< solid grayscale color frame */
+ FRAME_SOLID_COLOR = 6, /*!< solid non-grayscale color frame */
+ FRAME_OLD_ARITH_RGB = 7, /*!< obsolete arithmetic coded RGB (no longer encoded by upstream since version 1.1.0) */
+ FRAME_ARITH_RGBA = 8, /*!< arithmetic coded RGBA */
+ FRAME_SOLID_RGBA = 9, /*!< solid RGBA color frame */
+ FRAME_ARITH_YV12 = 10, /*!< arithmetic coded YV12 */
+ FRAME_REDUCED_RES = 11, /*!< reduced resolution YV12 frame */
+};
+
+typedef struct LagarithContext {
+ AVCodecContext *avctx;
+ AVFrame picture;
+ DSPContext dsp;
+ int zeros; /*!< number of consecutive zero bytes encountered */
+ int zeros_rem; /*!< number of zero bytes remaining to output */
+} LagarithContext;
+
+/**
+ * Compute the 52bit mantissa of 1/(double)denom.
+ * This crazy format uses floats in an entropy coder and we have to match x86
+ * rounding exactly, thus ordinary floats aren't portable enough.
+ * @param denom denominator
+ * @return 52bit mantissa
+ * @see softfloat_mul
+ */
+static uint64_t softfloat_reciprocal(uint32_t denom)
+{
+ int shift = av_log2(denom - 1) + 1;
+ uint64_t ret = (1ULL << 52) / denom;
+ uint64_t err = (1ULL << 52) - ret * denom;
+ ret <<= shift;
+ err <<= shift;
+ err += denom / 2;
+ return ret + err / denom;
+}
+
+/**
+ * (uint32_t)(x*f), where f has the given mantissa, and exponent 0
+ * Used in combination with softfloat_reciprocal computes x/(double)denom.
+ * @param x 32bit integer factor
+ * @param mantissa mantissa of f with exponent 0
+ * @return 32bit integer value (x*f)
+ * @see softfloat_reciprocal
+ */
+static uint32_t softfloat_mul(uint32_t x, uint64_t mantissa)
+{
+ uint64_t l = x * (mantissa & 0xffffffff);
+ uint64_t h = x * (mantissa >> 32);
+ h += l >> 32;
+ l &= 0xffffffff;
+ l += 1 << av_log2(h >> 21);
+ h += l >> 32;
+ return h >> 20;
+}
+
+static uint8_t lag_calc_zero_run(int8_t x)
+{
+ return (x << 1) ^ (x >> 7);
+}
+
+static int lag_decode_prob(GetBitContext *gb, uint32_t *value)
+{
+ static const uint8_t series[] = { 1, 2, 3, 5, 8, 13, 21 };
+ int i;
+ int bit = 0;
+ int bits = 0;
+ int prevbit = 0;
+ unsigned val;
+
+ for (i = 0; i < 7; i++) {
+ if (prevbit && bit)
+ break;
+ prevbit = bit;
+ bit = get_bits1(gb);
+ if (bit && !prevbit)
+ bits += series[i];
+ }
+ bits--;
+ if (bits < 0 || bits > 31) {
+ *value = 0;
+ return -1;
+ } else if (bits == 0) {
+ *value = 0;
+ return 0;
+ }
+
+ val = get_bits_long(gb, bits);
+ val |= 1 << bits;
+
+ *value = val - 1;
+
+ return 0;
+}
+
+static int lag_read_prob_header(lag_rac *rac, GetBitContext *gb)
+{
+ int i, j, scale_factor;
+ unsigned prob, cumulative_target;
+ unsigned cumul_prob = 0;
+ unsigned scaled_cumul_prob = 0;
+
+ rac->prob[0] = 0;
+ rac->prob[257] = UINT_MAX;
+ /* Read probabilities from bitstream */
+ for (i = 1; i < 257; i++) {
+ if (lag_decode_prob(gb, &rac->prob[i]) < 0) {
+ av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability encountered.\n");
+ return -1;
+ }
+ if ((uint64_t)cumul_prob + rac->prob[i] > UINT_MAX) {
+ av_log(rac->avctx, AV_LOG_ERROR, "Integer overflow encountered in cumulative probability calculation.\n");
+ return -1;
+ }
+ cumul_prob += rac->prob[i];
+ if (!rac->prob[i]) {
+ if (lag_decode_prob(gb, &prob)) {
+ av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability run encountered.\n");
+ return -1;
+ }
+ if (prob > 257 - i)
+ prob = 257 - i;
+ for (j = 0; j < prob; j++)
+ rac->prob[++i] = 0;
+ }
+ }
+
+ if (!cumul_prob) {
+ av_log(rac->avctx, AV_LOG_ERROR, "All probabilities are 0!\n");
+ return -1;
+ }
+
+ /* Scale probabilities so cumulative probability is an even power of 2. */
+ scale_factor = av_log2(cumul_prob);
+
+ if (cumul_prob & (cumul_prob - 1)) {
+ uint64_t mul = softfloat_reciprocal(cumul_prob);
+ for (i = 1; i < 257; i++) {
+ rac->prob[i] = softfloat_mul(rac->prob[i], mul);
+ scaled_cumul_prob += rac->prob[i];
+ }
+
+ scale_factor++;
+ cumulative_target = 1 << scale_factor;
+
+ if (scaled_cumul_prob > cumulative_target) {
+ av_log(rac->avctx, AV_LOG_ERROR,
+ "Scaled probabilities are larger than target!\n");
+ return -1;
+ }
+
+ scaled_cumul_prob = cumulative_target - scaled_cumul_prob;
+
+ for (i = 1; scaled_cumul_prob; i = (i & 0x7f) + 1) {
+ if (rac->prob[i]) {
+ rac->prob[i]++;
+ scaled_cumul_prob--;
+ }
+ /* Comment from reference source:
+ * if (b & 0x80 == 0) { // order of operations is 'wrong'; it has been left this way
+ * // since the compression change is negligable and fixing it
+ * // breaks backwards compatibilty
+ * b =- (signed int)b;
+ * b &= 0xFF;
+ * } else {
+ * b++;
+ * b &= 0x7f;
+ * }
+ */
+ }
+ }
+
+ rac->scale = scale_factor;
+
+ /* Fill probability array with cumulative probability for each symbol. */
+ for (i = 1; i < 257; i++)
+ rac->prob[i] += rac->prob[i - 1];
+
+ return 0;
+}
+
+static void add_lag_median_prediction(uint8_t *dst, uint8_t *src1,
+ uint8_t *diff, int w, int *left,
+ int *left_top)
+{
+ /* This is almost identical to add_hfyu_median_prediction in dsputil.h.
+ * However the &0xFF on the gradient predictor yealds incorrect output
+ * for lagarith.
+ */
+ int i;
+ uint8_t l, lt;
+
+ l = *left;
+ lt = *left_top;
+
+ for (i = 0; i < w; i++) {
+ l = mid_pred(l, src1[i], l + src1[i] - lt) + diff[i];
+ lt = src1[i];
+ dst[i] = l;
+ }
+
+ *left = l;
+ *left_top = lt;
+}
+
+static void lag_pred_line(LagarithContext *l, uint8_t *buf,
+ int width, int stride, int line)
+{
+ int L, TL;
+
+ if (!line) {
+ /* Left prediction only for first line */
+ L = l->dsp.add_hfyu_left_prediction(buf + 1, buf + 1,
+ width - 1, buf[0]);
+ return;
+ } else if (line == 1) {
+ /* Second line, left predict first pixel, the rest of the line is median predicted */
+ /* FIXME: In the case of RGB this pixel is top predicted */
+ TL = buf[-stride];
+ } else {
+ /* Top left is 2 rows back, last pixel */
+ TL = buf[width - (2 * stride) - 1];
+ }
+ /* Left pixel is actually prev_row[width] */
+ L = buf[width - stride - 1];
+
+ add_lag_median_prediction(buf, buf - stride, buf,
+ width, &L, &TL);
+}
+
+static int lag_decode_line(LagarithContext *l, lag_rac *rac,
+ uint8_t *dst, int width, int stride,
+ int esc_count)
+{
+ int i = 0;
+ int ret = 0;
+
+ if (!esc_count)
+ esc_count = -1;
+
+ /* Output any zeros remaining from the previous run */
+handle_zeros:
+ if (l->zeros_rem) {
+ int count = FFMIN(l->zeros_rem, width - i);
+ memset(dst + i, 0, count);
+ i += count;
+ l->zeros_rem -= count;
+ }
+
+ while (i < width) {
+ dst[i] = lag_get_rac(rac);
+ ret++;
+
+ if (dst[i])
+ l->zeros = 0;
+ else
+ l->zeros++;
+
+ i++;
+ if (l->zeros == esc_count) {
+ int index = lag_get_rac(rac);
+ ret++;
+
+ l->zeros = 0;
+
+ l->zeros_rem = lag_calc_zero_run(index);
+ goto handle_zeros;
+ }
+ }
+ return ret;
+}
+
+static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,
+ const uint8_t *src, int width,
+ int esc_count)
+{
+ int i = 0;
+ int count;
+ uint8_t zero_run = 0;
+ const uint8_t *start = src;
+ uint8_t mask1 = -(esc_count < 2);
+ uint8_t mask2 = -(esc_count < 3);
+ uint8_t *end = dst + (width - 2);
+
+output_zeros:
+ if (l->zeros_rem) {
+ count = FFMIN(l->zeros_rem, width - i);
+ memset(dst, 0, count);
+ l->zeros_rem -= count;
+ dst += count;
+ }
+
+ while (dst < end) {
+ i = 0;
+ while (!zero_run && dst + i < end) {
+ i++;
+ zero_run =
+ !(src[i] | (src[i + 1] & mask1) | (src[i + 2] & mask2));
+ }
+ if (zero_run) {
+ zero_run = 0;
+ i += esc_count;
+ memcpy(dst, src, i);
+ dst += i;
+ l->zeros_rem = lag_calc_zero_run(src[i]);
+
+ src += i + 1;
+ goto output_zeros;
+ } else {
+ memcpy(dst, src, i);
+ src += i;
+ }
+ }
+ return start - src;
+}
+
+
+
+static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,
+ int width, int height, int stride,
+ const uint8_t *src, int src_size)
+{
+ int i = 0;
+ int read = 0;
+ uint32_t length;
+ uint32_t offset = 1;
+ int esc_count = src[0];
+ GetBitContext gb;
+ lag_rac rac;
+
+ rac.avctx = l->avctx;
+ l->zeros = 0;
+
+ if (esc_count < 4) {
+ length = width * height;
+ if (esc_count && AV_RL32(src + 1) < length) {
+ length = AV_RL32(src + 1);
+ offset += 4;
+ }
+
+ init_get_bits(&gb, src + offset, src_size * 8);
+
+ if (lag_read_prob_header(&rac, &gb) < 0)
+ return -1;
+
+ lag_rac_init(&rac, &gb, length - stride);
+
+ for (i = 0; i < height; i++)
+ read += lag_decode_line(l, &rac, dst + (i * stride), width,
+ stride, esc_count);
+
+ if (read > length)
+ av_log(l->avctx, AV_LOG_WARNING,
+ "Output more bytes than length (%d of %d)\n", read,
+ length);
+ } else if (esc_count < 8) {
+ esc_count -= 4;
+ if (esc_count > 0) {
+ /* Zero run coding only, no range coding. */
+ for (i = 0; i < height; i++)
+ src += lag_decode_zero_run_line(l, dst + (i * stride), src,
+ width, esc_count);
+ } else {
+ /* Plane is stored uncompressed */
+ for (i = 0; i < height; i++) {
+ memcpy(dst + (i * stride), src, width);
+ src += width;
+ }
+ }
+ } else if (esc_count == 0xff) {
+ /* Plane is a solid run of 0 bytes */
+ for (i = 0; i < height; i++)
+ memset(dst + i * stride, 0, width);
+ } else {
+ av_log(l->avctx, AV_LOG_ERROR,
+ "Invalid zero run escape code! (%#x)\n", esc_count);
+ return -1;
+ }
+
+ for (i = 0; i < height; i++) {
+ lag_pred_line(l, dst, width, stride, i);
+ dst += stride;
+ }
+
+ return 0;
+}
+
+/**
+ * Decode a frame.
+ * @param avctx codec context
+ * @param data output AVFrame
+ * @param data_size size of output data or 0 if no picture is returned
+ * @param avpkt input packet
+ * @return number of consumed bytes on success or negative if decode fails
+ */
+static int lag_decode_frame(AVCodecContext *avctx,
+ void *data, int *data_size, AVPacket *avpkt)
+{
+ const uint8_t *buf = avpkt->data;
+ int buf_size = avpkt->size;
+ LagarithContext *l = avctx->priv_data;
+ AVFrame *const p = &l->picture;
+ uint8_t frametype = 0;
+ uint32_t offset_gu = 0, offset_bv = 0, offset_ry = 9;
+
+ AVFrame *picture = data;
+
+ if (p->data[0])
+ avctx->release_buffer(avctx, p);
+
+ p->reference = 0;
+ p->key_frame = 1;
+
+ frametype = buf[0];
+
+ offset_gu = AV_RL32(buf + 1);
+ offset_bv = AV_RL32(buf + 5);
+
+ switch (frametype) {
+ case FRAME_ARITH_YV12:
+ avctx->pix_fmt = PIX_FMT_YUV420P;
+
+ if (avctx->get_buffer(avctx, p) < 0) {
+ av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
+ return -1;
+ }
+
+ lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
+ p->linesize[0], buf + offset_ry,
+ buf_size);
+ lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
+ avctx->height / 2, p->linesize[2],
+ buf + offset_gu, buf_size);
+ lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
+ avctx->height / 2, p->linesize[1],
+ buf + offset_bv, buf_size);
+ break;
+ default:
+ av_log(avctx, AV_LOG_ERROR,
+ "Unsupported Lagarith frame type: %#x\n", frametype);
+ return -1;
+ }
+
+ *picture = *p;
+ *data_size = sizeof(AVFrame);
+
+ return buf_size;
+}
+
+static av_cold int lag_decode_init(AVCodecContext *avctx)
+{
+ LagarithContext *l = avctx->priv_data;
+ l->avctx = avctx;
+
+ dsputil_init(&l->dsp, avctx);
+
+ return 0;
+}
+
+static av_cold int lag_decode_end(AVCodecContext *avctx)
+{
+ LagarithContext *l = avctx->priv_data;
+
+ if (l->picture.data[0])
+ avctx->release_buffer(avctx, &l->picture);
+
+ return 0;
+}
+
+AVCodec lagarith_decoder = {
+ "lagarith",
+ CODEC_TYPE_VIDEO,
+ CODEC_ID_LAGARITH,
+ sizeof(LagarithContext),
+ lag_decode_init,
+ NULL,
+ lag_decode_end,
+ lag_decode_frame,
+ CODEC_CAP_DR1,
+ .long_name = NULL_IF_CONFIG_SMALL("Lagarith lossless"),
+};
diff --git a/libavcodec/lagarithrac.c b/libavcodec/lagarithrac.c
new file mode 100644
index 0000000..0cbc3b8
--- /dev/null
+++ b/libavcodec/lagarithrac.c
@@ -0,0 +1,58 @@
+/*
+ * Lagarith range decoder
+ * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
+ * Copyright (c) 2009 David Conrad
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file libavcodec/lagarithrac.c
+ * Lagarith range decoder
+ * @author Nathan Caldwell
+ * @author David Conrad
+ */
+
+#include "get_bits.h"
+#include "lagarithrac.h"
+
+void lag_rac_init(lag_rac *l, GetBitContext *gb, int length)
+{
+ int i, j;
+
+ /* According to reference decoder "1st byte is garbage",
+ * however, it gets skipped by the call to align_get_bits()
+ */
+ align_get_bits(gb);
+ l->bytestream_start =
+ l->bytestream = gb->buffer + get_bits_count(gb) / 8;
+ l->bytestream_end = l->bytestream_start + length;
+
+ l->range = 0x80;
+ l->low = *l->bytestream >> 1;
+ l->hash_shift = FFMAX(l->scale - 8, 0);
+
+ for (i = j = 0; i < 256; i++) {
+ unsigned r = i << l->hash_shift;
+ while (l->prob[j + 1] <= r)
+ j++;
+ l->range_hash[i] = j;
+ }
+
+ /* Add conversion factor to hash_shift so we don't have to in lag_get_rac. */
+ l->hash_shift += 23;
+}
diff --git a/libavcodec/lagarithrac.h b/libavcodec/lagarithrac.h
new file mode 100644
index 0000000..d985b60
--- /dev/null
+++ b/libavcodec/lagarithrac.h
@@ -0,0 +1,116 @@
+/*
+ * Lagarith range decoder
+ * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
+ * Copyright (c) 2009 David Conrad
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file libavcodec/lagarithrac.h
+ * Lagarith range decoder
+ * @author Nathan Caldwell
+ * @author David Conrad
+ */
+
+#ifndef AVCODEC_LAGARITHRAC_H
+#define AVCODEC_LAGARITHRAC_H
+
+#include <stdint.h>
+#include "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+#include "avcodec.h"
+#include "get_bits.h"
+
+typedef struct lag_rac {
+ AVCodecContext *avctx;
+ unsigned low;
+ unsigned range;
+ unsigned scale; /*!< Number of bits of precision in range. */
+ unsigned hash_shift; /*!< Number of bits to shift to calculate hash for radix search. */
+
+ const uint8_t *bytestream_start; /*!< Start of input bytestream. */
+ const uint8_t *bytestream; /*!< Current position in input bytestream. */
+ const uint8_t *bytestream_end; /*!< End position of input bytestream. */
+
+ uint32_t prob[258]; /*!< Table of cumulative probability for each symbol. */
+ uint8_t range_hash[256]; /*!< Hash table mapping upper byte to approximate symbol. */
+} lag_rac;
+
+void lag_rac_init(lag_rac *l, GetBitContext *gb, int length);
+
+/* TODO: Optimize */
+static inline void lag_rac_refill(lag_rac *l)
+{
+ while (l->range <= 0x800000) {
+ l->low <<= 8;
+ l->range <<= 8;
+ l->low |= 0xff & (AV_RB16(l->bytestream) >> 1);
+ if (l->bytestream < l->bytestream_end)
+ l->bytestream++;
+ }
+}
+
+/**
+ * Decode a single byte from the compressed plane described by *l.
+ * @param l pointer to lag_rac for the current plane
+ * @return next byte of decoded data
+ */
+static inline uint8_t lag_get_rac(lag_rac *l)
+{
+ unsigned range_scaled, low_scaled, div;
+ int val;
+ uint8_t shift;
+
+ lag_rac_refill(l);
+
+ range_scaled = l->range >> l->scale;
+
+ if (l->low < range_scaled * l->prob[255]) {
+ /* val = 0 is frequent enough to deserve a shortcut */
+ if (l->low < range_scaled * l->prob[1]) {
+ val = 0;
+ } else {
+ /* FIXME __builtin_clz is ~20% faster here, but not allowed in generic code. */
+ shift = 30 - av_log2(range_scaled);
+ div = ((range_scaled << shift) + (1 << 23) - 1) >> 23;
+ /* low>>24 ensures that any cases too big for exact FASTDIV are
+ * under- rather than over-estimated
+ */
+ low_scaled = FASTDIV(l->low - (l->low >> 24), div);
+ shift -= l->hash_shift;
+ shift &= 31;
+ low_scaled = (low_scaled << shift) | (low_scaled >> (32 - shift));
+ /* low_scaled is now a lower bound of low/range_scaled */
+ val = l->range_hash[(uint8_t) low_scaled];
+ while (l->low >= range_scaled * l->prob[val + 1])
+ val++;
+ }
+
+ l->range = range_scaled * (l->prob[val + 1] - l->prob[val]);
+ } else {
+ val = 255;
+ l->range -= range_scaled * l->prob[255];
+ }
+
+ l->low -= range_scaled * l->prob[val];
+
+ return val;
+}
+
+
+#endif /* AVCODEC_LAGARITHRAC_H */
diff --git a/libavformat/riff.c b/libavformat/riff.c
index f81260a..7388f9c 100644
--- a/libavformat/riff.c
+++ b/libavformat/riff.c
@@ -257,6 +257,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
{ CODEC_ID_AURA2, MKTAG('A', 'U', 'R', '2') },
{ CODEC_ID_DPX, MKTAG('d', 'p', 'x', ' ') },
{ CODEC_ID_KGV1, MKTAG('K', 'G', 'V', '1') },
+ { CODEC_ID_LAGARITH, MKTAG('L', 'A', 'G', 'S') },
{ CODEC_ID_NONE, 0 }
};
--
Libav/FFmpeg packaging
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