8SVX decoder

Patch by Jai Menon (realityman <at> gmx.net)

Originally committed as revision 12632 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 114 insertions, 0 deletions

diff --git a/libavcodec/8svx.c b/libavcodec/8svx.c
new file mode 100644
index 0000000000..1c98a7ec74
--- /dev/null
+++ b/libavcodec/8svx.c
@@ -0,0 +1,114 @@
+/*
+ * 8SVX Audio Decoder
+ * Copyright (C) 2008 Jaikrishnan Menon
+ *
+ * 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 8svx.c
+ * 8svx audio decoder
+ * @author Jaikrishnan Menon
+ * supports: fibonacci delta encoding
+ *         : exponential encoding
+ */
+
+#include "avcodec.h"
+
+/**
+ * decoder context
+ */
+typedef struct EightSvxContext {
+    int16_t fib_acc;
+    int16_t *table;
+} EightSvxContext;
+
+const static int16_t fibonacci[16]   = { -34<<8, -21<<8, -13<<8,  -8<<8, -5<<8, -3<<8, -2<<8, -1<<8,
+                                          0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 };
+const static int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8,
+                                          0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 };
+
+/**
+ * decode a frame
+ */
+static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
+                                 const uint8_t *buf, int buf_size)
+{
+    EightSvxContext *esc = avctx->priv_data;
+    int16_t *out_data = data;
+    int consumed = buf_size;
+    const uint8_t *buf_end = buf + buf_size;
+
+    if((*data_size >> 2) < buf_size)
+        return -1;
+
+    if(avctx->frame_number == 0) {
+        esc->fib_acc = buf[1] << 8;
+        buf_size -= 2;
+        buf += 2;
+    }
+
+    *data_size = buf_size << 2;
+
+    while(buf < buf_end) {
+        uint8_t d = *buf++;
+        esc->fib_acc += esc->table[d & 0x0f];
+        *out_data++ = esc->fib_acc;
+        esc->fib_acc += esc->table[d >> 4];
+        *out_data++ = esc->fib_acc;
+    }
+
+    return consumed;
+}
+
+/**
+ * initialize 8svx decoder
+ */
+static av_cold int eightsvx_decode_init(AVCodecContext *avctx)
+{
+    EightSvxContext *esc = avctx->priv_data;
+
+    switch(avctx->codec->id) {
+        case CODEC_ID_8SVX_FIB:
+          esc->table = fibonacci;
+          break;
+        case CODEC_ID_8SVX_EXP:
+          esc->table = exponential;
+          break;
+        default:
+          return -1;
+    }
+    return 0;
+}
+
+AVCodec eightsvx_fib_decoder = {
+  .name           = "8svx fibonacci decoder",
+  .type           = CODEC_TYPE_AUDIO,
+  .id             = CODEC_ID_8SVX_FIB,
+  .priv_data_size = sizeof (EightSvxContext),
+  .init           = eightsvx_decode_init,
+  .decode         = eightsvx_decode_frame,
+};
+
+AVCodec eightsvx_exp_decoder = {
+  .name           = "8svx exponential decoder",
+  .type           = CODEC_TYPE_AUDIO,
+  .id             = CODEC_ID_8SVX_EXP,
+  .priv_data_size = sizeof (EightSvxContext),
+  .init           = eightsvx_decode_init,
+  .decode         = eightsvx_decode_frame,
+};