avcodec: add AV1 packet split API

Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/libavcodec/av1_parse.h b/libavcodec/av1_parse.h
new file mode 100644
index 0000000000..84fc71c925
--- /dev/null
+++ b/libavcodec/av1_parse.h
@@ -0,0 +1,126 @@
+/*
+ * AV1 common parsing code
+ *
+ * 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
+ */
+
+#ifndef AVCODEC_AV1_PARSE_H
+#define AVCODEC_AV1_PARSE_H
+
+#include <stdint.h>
+
+#include "avcodec.h"
+#include "get_bits.h"
+
+typedef struct AV1OBU {
+    /** Size of payload */
+    int size;
+    const uint8_t *data;
+
+    /** Size of entire OBU, including header */
+    int raw_size;
+    const uint8_t *raw_data;
+
+    /** GetBitContext initialized to the start of the payload */
+    GetBitContext gb;
+
+    int type;
+
+    int temporal_id;
+    int spatial_id;
+} AV1OBU;
+
+/** An input packet split into OBUs */
+typedef struct AV1Packet {
+    AV1OBU *obus;
+    int nb_obus;
+    int obus_allocated;
+} AV1Packet;
+
+/**
+ * Extract an OBU from a raw bitstream.
+ *
+ * @note This function does not copy or store any bistream data. All
+ *       the pointers in the AV1OBU structure will be valid as long
+ *       as the input buffer also is.
+ */
+int ff_av1_extract_obu(AV1OBU *obu, const uint8_t *buf, int length,
+                       void *logctx);
+
+/**
+ * Split an input packet into OBUs.
+ *
+ * @note This function does not copy or store any bistream data. All
+ *       the pointers in the AV1Packet structure will be valid as
+ *       long as the input buffer also is.
+ */
+int ff_av1_packet_split(AV1Packet *pkt, const uint8_t *buf, int length,
+                        void *logctx);
+
+/**
+ * Free all the allocated memory in the packet.
+ */
+void ff_av1_packet_uninit(AV1Packet *pkt);
+
+static inline int64_t leb128(GetBitContext *gb) {
+    int64_t ret = 0;
+    int i;
+
+    for (i = 0; i < 8; i++) {
+        int byte = get_bits(gb, 8);
+        ret |= (int64_t)(byte & 0x7f) << (i * 7);
+        if (!(byte & 0x80))
+            break;
+    }
+    return ret;
+}
+
+static inline int parse_obu_header(const uint8_t *buf, int buf_size,
+                                   int64_t *obu_size, int *start_pos, int *type,
+                                   int *temporal_id, int *spatial_id)
+{
+    GetBitContext gb;
+    int ret, extension_flag, has_size_flag;
+
+    ret = init_get_bits8(&gb, buf, FFMIN(buf_size, 2 + 8)); // OBU header fields + max leb128 length
+    if (ret < 0)
+        return ret;
+
+    if (get_bits1(&gb) != 0) // obu_forbidden_bit
+        return AVERROR_INVALIDDATA;
+
+    *type      = get_bits(&gb, 4);
+    extension_flag = get_bits1(&gb);
+    has_size_flag  = get_bits1(&gb);
+    skip_bits1(&gb); // obu_reserved_1bit
+
+    if (extension_flag) {
+        *temporal_id = get_bits(&gb, 3);
+        *spatial_id  = get_bits(&gb, 2);
+        skip_bits(&gb, 3); // extension_header_reserved_3bits
+    } else {
+        *temporal_id = *spatial_id = 0;
+    }
+
+    *obu_size  = has_size_flag ? leb128(&gb)
+                               : buf_size - 1 - extension_flag;
+    *start_pos = get_bits_count(&gb) / 8;
+
+    return 0;
+}
+
+#endif /* AVCODEC_AV1_PARSE_H */