Initial revision

Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 189 insertions, 0 deletions

diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
new file mode 100644
index 0000000000..7332a11d8e
--- /dev/null
+++ b/libavcodec/ac3dec.c
@@ -0,0 +1,189 @@
+/*
+ * AC3 decoder
+ * Copyright (c) 2001 Gerard Lantau.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "avcodec.h"
+
+#include <inttypes.h>
+#include "libac3/ac3.h"
+
+/* currently, I use libac3 which is Copyright (C) Aaron Holtzman and
+   released under the GPL license. I may reimplement it someday... */
+typedef struct AC3DecodeState {
+    UINT8 inbuf[4096]; /* input buffer */
+    UINT8 *inbuf_ptr;
+    int frame_size;
+    int flags;
+    ac3_state_t state;
+} AC3DecodeState;
+
+static int ac3_decode_init(AVCodecContext *avctx)
+{
+    AC3DecodeState *s = avctx->priv_data;
+
+    ac3_init ();
+    s->inbuf_ptr = s->inbuf;
+    s->frame_size = 0;
+    return 0;
+}
+
+stream_samples_t samples;
+
+/**** the following two functions comes from ac3dec */
+static inline int blah (int32_t i)
+{
+    if (i > 0x43c07fff)
+	return 32767;
+    else if (i < 0x43bf8000)
+	return -32768;
+    else
+	return i - 0x43c00000;
+}
+
+static inline void float_to_int (float * _f, INT16 * s16) 
+{
+    int i;
+    int32_t * f = (int32_t *) _f;	// XXX assumes IEEE float format
+
+    for (i = 0; i < 256; i++) {
+	s16[2*i] = blah (f[i]);
+	s16[2*i+1] = blah (f[i+256]);
+    }
+}
+
+static inline void float_to_int_mono (float * _f, INT16 * s16) 
+{
+    int i;
+    int32_t * f = (int32_t *) _f;	// XXX assumes IEEE float format
+
+    for (i = 0; i < 256; i++) {
+	s16[i] = blah (f[i]);
+    }
+}
+
+/**** end */
+
+#define HEADER_SIZE 7
+
+static int ac3_decode_frame(AVCodecContext *avctx, 
+                            void *data, int *data_size,
+                            UINT8 *buf, int buf_size)
+{
+    AC3DecodeState *s = avctx->priv_data;
+    UINT8 *buf_ptr;
+    int flags, i, len;
+    int sample_rate, bit_rate;
+    short *out_samples = data;
+    float level;
+
+    *data_size = 0;
+    buf_ptr = buf;
+    while (buf_size > 0) {
+        len = s->inbuf_ptr - s->inbuf;
+        if (s->frame_size == 0) {
+            /* no header seen : find one. We need at least 7 bytes to parse it */
+            len = HEADER_SIZE - len;
+            if (len > buf_size)
+                len = buf_size;
+            memcpy(s->inbuf_ptr, buf_ptr, len);
+            buf_ptr += len;
+            s->inbuf_ptr += len;
+            buf_size -= len;
+            if ((s->inbuf_ptr - s->inbuf) == HEADER_SIZE) {
+                len = ac3_syncinfo (s->inbuf, &s->flags, &sample_rate, &bit_rate);
+                if (len == 0) {
+                    /* no sync found : move by one byte (inefficient, but simple!) */
+                    memcpy(s->inbuf, s->inbuf + 1, HEADER_SIZE - 1);
+                    s->inbuf_ptr--;
+                } else {
+                    s->frame_size = len;
+                    /* update codec info */
+                    avctx->sample_rate = sample_rate;
+                    if ((s->flags & AC3_CHANNEL_MASK) == AC3_MONO)
+                        avctx->channels = 1;
+                    else
+                        avctx->channels = 2;
+                    avctx->bit_rate = bit_rate;
+                }
+            }
+        } else if (len < s->frame_size) {
+            len = s->frame_size - len;
+            if (len > buf_size)
+                len = buf_size;
+            
+            memcpy(s->inbuf_ptr, buf_ptr, len);
+            buf_ptr += len;
+            s->inbuf_ptr += len;
+            buf_size -= len;
+        } else {
+            if (avctx->channels == 1)
+                flags = AC3_MONO;
+            else
+                flags = AC3_STEREO;
+
+            flags |= AC3_ADJUST_LEVEL;
+            level = 1;
+            if (ac3_frame (&s->state, s->inbuf, &flags, &level, 384)) {
+            fail:
+                s->inbuf_ptr = s->inbuf;
+                s->frame_size = 0;
+                continue;
+            }
+            for (i = 0; i < 6; i++) {
+                if (ac3_block (&s->state))
+                    goto fail;
+                if (avctx->channels == 1)
+                    float_to_int_mono (*samples, out_samples + i * 256);
+                else
+                    float_to_int (*samples, out_samples + i * 512);
+            }
+            s->inbuf_ptr = s->inbuf;
+            s->frame_size = 0;
+            *data_size = 6 * avctx->channels * 256 * sizeof(INT16);
+            break;
+        }
+    }
+    return buf_ptr - buf;
+}
+
+static int ac3_decode_end(AVCodecContext *s)
+{
+    return 0;
+}
+
+AVCodec ac3_decoder = {
+    "ac3",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_AC3,
+    sizeof(AC3DecodeState),
+    ac3_decode_init,
+    NULL,
+    ac3_decode_end,
+    ac3_decode_frame,
+};
+
+/* register codecs which could clash with mplayer symbols */
+/* XXX: rename all symbols to avoid clashed */
+void avcodec_register_more(void)
+{
+    register_avcodec(&mp3_decoder);
+    register_avcodec(&ac3_decoder);
+}
+