[FFmpeg-devel,1/5] avcodec: add AV1 packet split API

Submitted by James Almer on July 9, 2018, 6:26 p.m.

Details

Message ID 20180709182654.9996-2-jamrial@gmail.com
State New
Headers show

Commit Message

James Almer July 9, 2018, 6:26 p.m.
Signed-off-by: James Almer <jamrial@gmail.com>
---
I talked with Mark Thompson about AV1 parsing code in libavcodec and
he told me he prefered to keep everything within his upcoming CBS
implementation. I very much agree the eventual decoder and avparser
should use it given they will require deep bitstream parsing, but
for the upcoming changes i only require to split the OBUs in a packet
(Which require minimal OBU header parsing to find where each one of
them start and end), so the overhead of parsing and writing full CBS
packets seem unnecesary.
This way i also have an inline function ready to be used in muxer
related libavformat code.

If there are still strong opinions about having AV1 parsing code in
avcodec separate from CBS, even if minimal, then I can reimplement
extract_extradata using the latter and move the header parsing code
to libavformat.

 libavcodec/av1_parse.c | 103 +++++++++++++++++++++++++++++++++
 libavcodec/av1_parse.h | 126 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 229 insertions(+)
 create mode 100644 libavcodec/av1_parse.c
 create mode 100644 libavcodec/av1_parse.h

Patch hide | download patch | download mbox

diff --git a/libavcodec/av1_parse.c b/libavcodec/av1_parse.c
new file mode 100644
index 0000000000..48feb9fb8a
--- /dev/null
+++ b/libavcodec/av1_parse.c
@@ -0,0 +1,103 @@ 
+/*
+ * 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
+ */
+
+#include "config.h"
+
+#include "libavutil/mem.h"
+
+#include "av1_parse.h"
+#include "bytestream.h"
+
+int ff_av1_extract_obu(AV1OBU *obu, const uint8_t *buf, int length, void *logctx)
+{
+    int64_t obu_size;
+    int start_pos, type, temporal_id, spatial_id;
+
+    int ret = parse_obu_header(buf, length, &obu_size, &start_pos,
+                               &type, &temporal_id, &spatial_id);
+    if (ret < 0)
+        return ret;
+
+    if (obu_size > INT_MAX / 8 || obu_size < 0)
+        return AVERROR(ERANGE);
+
+    obu->type        = type;
+    obu->temporal_id = temporal_id;
+    obu->spatial_id  = spatial_id;
+
+    length = obu_size + start_pos;
+
+    obu->data     = buf + start_pos;
+    obu->size     = obu_size;
+    obu->raw_data = buf;
+    obu->raw_size = length;
+
+    ret = init_get_bits(&obu->gb, obu->data, obu->size * 8);
+    if (ret < 0)
+        return ret;
+
+    av_log(logctx, AV_LOG_DEBUG,
+           "obu_type: %d, temporal_id: %d, spatial_id: %d, payload size: %d\n",
+           obu->type, obu->temporal_id, obu->spatial_id, obu->size);
+
+    return length;
+}
+
+int ff_av1_packet_split(AV1Packet *pkt, const uint8_t *buf, int length, void *logctx)
+{
+    GetByteContext bc;
+    int consumed;
+
+    bytestream2_init(&bc, buf, length);
+    pkt->nb_obus = 0;
+
+    while (bytestream2_get_bytes_left(&bc) > 0) {
+        AV1OBU *obu;
+
+        if (pkt->obus_allocated < pkt->nb_obus + 1) {
+            int new_size = pkt->obus_allocated + 1;
+            AV1OBU *tmp = av_realloc_array(pkt->obus, new_size, sizeof(*tmp));
+            if (!tmp)
+                return AVERROR(ENOMEM);
+
+            pkt->obus = tmp;
+            memset(pkt->obus + pkt->obus_allocated, 0,
+                   (new_size - pkt->obus_allocated) * sizeof(*tmp));
+            pkt->obus_allocated = new_size;
+        }
+        obu = &pkt->obus[pkt->nb_obus];
+
+        consumed = ff_av1_extract_obu(obu, bc.buffer, bytestream2_get_bytes_left(&bc), logctx);
+        if (consumed < 0)
+            return consumed;
+
+        pkt->nb_obus++;
+
+        bytestream2_skip(&bc, consumed);
+    }
+
+    return 0;
+}
+
+void ff_av1_packet_uninit(AV1Packet *pkt)
+{
+    av_freep(&pkt->obus);
+    pkt->obus_allocated = 0;
+}
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 */