--- /dev/null
+/*
+ * AC3 decoder
+ * Copyright (c) 2001 Fabrice Bellard.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/**
+ * @file ac3dec.c
+ * AC3 decoder.
+ */
+
+//#define DEBUG
+
+#include "avcodec.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_t inbuf[4096]; /* input buffer */
+ uint8_t *inbuf_ptr;
+ int frame_size;
+ int flags;
+ int channels;
+ 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_t * s16, int nchannels)
+{
+ int i, j, c;
+ int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format
+
+ j = 0;
+ nchannels *= 256;
+ for (i = 0; i < 256; i++) {
+ for (c = 0; c < nchannels; c += 256)
+ s16[j++] = blah (f[i + c]);
+ }
+}
+
+/**** end */
+
+#define HEADER_SIZE 7
+
+static int ac3_decode_frame(AVCodecContext *avctx,
+ void *data, int *data_size,
+ uint8_t *buf, int buf_size)
+{
+ AC3DecodeState *s = avctx->priv_data;
+ uint8_t *buf_ptr;
+ int flags, i, len;
+ int sample_rate, bit_rate;
+ short *out_samples = data;
+ float level;
+ static const int ac3_channels[8] = {
+ 2, 1, 2, 3, 3, 4, 4, 5
+ };
+
+ *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;
+ s->channels = ac3_channels[s->flags & 7];
+ if (s->flags & AC3_LFE)
+ s->channels++;
+ if (avctx->channels == 0)
+ /* No specific number of channel requested */
+ avctx->channels = s->channels;
+ else if (s->channels < avctx->channels) {
+ fprintf(stderr, "ac3dec: AC3 Source channels are less than specified: output to %d channels.. (frmsize: %d)\n", s->channels, len);
+ avctx->channels = s->channels;
+ }
+ 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 {
+ flags = s->flags;
+ if (avctx->channels == 1)
+ flags = AC3_MONO;
+ else if (avctx->channels == 2)
+ flags = AC3_STEREO;
+ else
+ 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;
+ float_to_int (*samples, out_samples + i * 256 * avctx->channels, avctx->channels);
+ }
+ s->inbuf_ptr = s->inbuf;
+ s->frame_size = 0;
+ *data_size = 6 * avctx->channels * 256 * sizeof(int16_t);
+ 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,
+};
projects / synfig.git / blobdiff