avcodec: add amr parser

1 files changed, 103 insertions, 0 deletions

diff --git a/libavcodec/amr_parser.c b/libavcodec/amr_parser.c
new file mode 100644
index 0000000000..2659cb40d7
--- /dev/null
+++ b/libavcodec/amr_parser.c
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2021 Paul B Mahol
+ *
+ * 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
+ * AMR audio parser
+ *
+ * Splits packets into individual blocks.
+ */
+
+#include "libavutil/intreadwrite.h"
+#include "parser.h"
+
+static const uint8_t amrnb_packed_size[16] = {
+    13, 14, 16, 18, 20, 21, 27, 32, 6, 1, 1, 1, 1, 1, 1, 1
+};
+static const uint8_t amrwb_packed_size[16] = {
+    18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 1, 1, 1, 1, 1, 1
+};
+
+typedef struct AMRParseContext {
+    ParseContext pc;
+    uint64_t cumulated_size;
+    uint64_t block_count;
+    int remaining;
+} AMRParseContext;
+
+static int amr_parse(AVCodecParserContext *s1,
+                     AVCodecContext *avctx,
+                     const uint8_t **poutbuf, int *poutbuf_size,
+                     const uint8_t *buf, int buf_size)
+{
+    AMRParseContext *s = s1->priv_data;
+    ParseContext *pc = &s->pc;
+    int next = END_NOT_FOUND;
+
+    *poutbuf_size = 0;
+    *poutbuf = NULL;
+
+    if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
+        next = buf_size;
+    } else {
+        if (s->remaining) {
+            next = s->remaining;
+        } else {
+            int mode = (buf[0] >> 3) & 0x0F;
+
+            if (avctx->codec_id == AV_CODEC_ID_AMR_NB) {
+                next = amrnb_packed_size[mode];
+            } else if (avctx->codec_id == AV_CODEC_ID_AMR_WB) {
+                next = amrwb_packed_size[mode];
+            }
+        }
+
+        s->remaining = next - FFMIN(buf_size, next);
+        if (s->remaining)
+            next = END_NOT_FOUND;
+
+        if (next != END_NOT_FOUND) {
+            if (s->cumulated_size < UINT64_MAX - next) {
+                s->cumulated_size += next;
+                /* Both AMR formats have 50 frames per second */
+                avctx->bit_rate = s->cumulated_size / ++s->block_count * 8 * 50;
+            }
+        }
+
+        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
+            *poutbuf      = NULL;
+            *poutbuf_size = 0;
+            return buf_size;
+        }
+    }
+
+    s1->duration = avctx->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
+
+    *poutbuf = buf;
+    *poutbuf_size = buf_size;
+    return next;
+}
+
+const AVCodecParser ff_amr_parser = {
+    .codec_ids      = { AV_CODEC_ID_AMR_NB, AV_CODEC_ID_AMR_WB },
+    .priv_data_size = sizeof(AMRParseContext),
+    .parser_parse   = amr_parse,
+    .parser_close   = ff_parse_close,
+};