Add single stream LATM/LOAS decoder

The decoder is just a wrapper around the AAC decoder.
based on patch by Paul Kendall { paul <ät> kcbbs gen nz }

Originally committed as revision 25642 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 119 insertions, 0 deletions

diff --git a/libavcodec/latm_parser.c b/libavcodec/latm_parser.c
new file mode 100644
index 0000000..b8b67ef
--- /dev/null
+++ b/libavcodec/latm_parser.c
@@ -0,0 +1,119 @@
+/*
+ * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz>
+ *
+ * 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
+ * AAC LATM parser
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <sys/types.h>
+
+#include "parser.h"
+
+#define LATM_HEADER     0x56e000        // 0x2b7 (11 bits)
+#define LATM_MASK       0xFFE000        // top 11 bits
+#define LATM_SIZE_MASK  0x001FFF        // bottom 13 bits
+
+typedef struct LATMParseContext{
+    ParseContext pc;
+    int count;
+} LATMParseContext;
+
+/**
+ * finds the end of the current frame in the bitstream.
+ * @return the position of the first byte of the next frame, or -1
+ */
+static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf,
+                               int buf_size)
+{
+    LATMParseContext *s = s1->priv_data;
+    ParseContext *pc    = &s->pc;
+    int pic_found, i;
+    uint32_t state;
+
+    pic_found = pc->frame_start_found;
+    state     = pc->state;
+
+    i = 0;
+    if (!pic_found) {
+        for (i = 0; i < buf_size; i++) {
+            state = (state<<8) | buf[i];
+            if ((state & LATM_MASK) == LATM_HEADER) {
+                i++;
+                s->count  = -i;
+                pic_found = 1;
+                break;
+            }
+        }
+    }
+
+    if (pic_found) {
+        /* EOF considered as end of frame */
+        if (buf_size == 0)
+            return 0;
+        if ((state & LATM_SIZE_MASK) - s->count <= buf_size) {
+            pc->frame_start_found = 0;
+            pc->state             = -1;
+            return (state & LATM_SIZE_MASK) - s->count;
+        }
+    }
+
+    s->count             += buf_size;
+    pc->frame_start_found = pic_found;
+    pc->state             = state;
+
+    return END_NOT_FOUND;
+}
+
+static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
+                      const uint8_t **poutbuf, int *poutbuf_size,
+                      const uint8_t *buf, int buf_size)
+{
+    LATMParseContext *s = s1->priv_data;
+    ParseContext *pc    = &s->pc;
+    int next;
+
+    if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
+        next = buf_size;
+    } else {
+        next = latm_find_frame_end(s1, buf, buf_size);
+
+        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
+            *poutbuf      = NULL;
+            *poutbuf_size = 0;
+            return buf_size;
+        }
+    }
+    *poutbuf      = buf;
+    *poutbuf_size = buf_size;
+    return next;
+}
+
+AVCodecParser aac_latm_parser = {
+    { CODEC_ID_AAC_LATM },
+    sizeof(LATMParseContext),
+    NULL,
+    latm_parse,
+    ff_parse_close
+};