[vlc-commits] demux: add AV1 sample unpacking helper

[Francois Cartegnie]

vlc | branch: master | Francois Cartegnie <fcvlcdev at free.fr> | Thu Oct 11 11:18:58 2018 +0200| [40634d07f1671c337e87d584d34234f15bc4899d] | committer: Francois Cartegnie

demux: add AV1 sample unpacking helper

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=40634d07f1671c337e87d584d34234f15bc4899d
---

 modules/demux/av1_unpack.h | 121 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)

diff --git a/modules/demux/av1_unpack.h b/modules/demux/av1_unpack.h
new file mode 100644
index 0000000000..683c53423d
--- /dev/null
+++ b/modules/demux/av1_unpack.h
@@ -0,0 +1,121 @@
+/*****************************************************************************
+ * av1_unpack.h: AV1 samples expander
+ *****************************************************************************
+ * Copyright (C) 2018 VideoLabs, VLC authors and VideoLAN
+ *
+ * This program 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.
+ *
+ * This program 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 program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+#ifndef VLC_AV1_UNPACK_H
+#define VLC_AV1_UNPACK_H
+
+#include "../packetizer/av1_obu.h"
+#include <vlc_common.h>
+#include <vlc_block.h>
+
+static inline uint8_t leb128_expected(uint32_t v)
+{
+    if     (v < (1U << 8))  return 1;
+    else if(v < (1U << 15)) return 2;
+    else if(v < (1U << 22)) return 3;
+    else if(v < (1U << 29)) return 4;
+    else                    return 5;
+}
+
+static inline void leb128_write(uint32_t v, uint8_t *p)
+{
+    for(;;)
+    {
+        *p = v & 0x7F;
+        v >>= 7;
+        if(v == 0)
+            break;
+        *p++ |= 0x80;
+    }
+}
+
+static inline block_t * AV1_Unpack_Sample_ExpandSize(block_t *p_block)
+{
+    AV1_OBU_iterator_ctx_t ctx;
+    AV1_OBU_iterator_init(&ctx, p_block->p_buffer, p_block->i_buffer);
+    const uint8_t *p_obu = NULL; size_t i_obu;
+    while(AV1_OBU_iterate_next(&ctx, &p_obu, &i_obu))
+    {
+        if(AV1_OBUHasSizeField(p_obu))
+            continue;
+        const uint8_t i_header = 1 + AV1_OBUHasExtensionField(p_obu);
+        const uint8_t i_sizelen = leb128_expected(i_obu - i_header);
+        const size_t i_obu_offset = p_obu - p_block->p_buffer;
+
+        /* Make room for i_sizelen after header */
+        if(2 * (i_obu_offset + i_header) + i_sizelen < p_block->i_buffer)
+        {
+            /* move data to the left */
+            p_block = block_Realloc(p_block, i_sizelen, p_block->i_buffer);
+            if(p_block)
+                memmove(p_block->p_buffer, &p_block->p_buffer[i_sizelen],
+                        i_obu_offset + i_header);
+        }
+        else
+        {
+            /* move data to the right */
+            p_block = block_Realloc(p_block, 0, p_block->i_buffer + i_sizelen);
+            if(p_block)
+            {
+                const size_t i_off = i_obu_offset + i_header;
+                memmove(&p_block->p_buffer[i_off + i_sizelen], &p_block->p_buffer[i_off],
+                        p_block->i_buffer - i_off - i_sizelen);
+            }
+        }
+
+        if(likely(p_block))
+        {
+            leb128_write(i_obu - i_header, &p_block->p_buffer[i_obu_offset + i_header]);
+            p_block->p_buffer[i_obu_offset] |= 0x02;
+        }
+
+        break;
+    }
+    return p_block;
+}
+
+/*
+    Restores TD OBU and last size field from MP4/MKV sample format
+    to full AV1 low overhead format.
+
+    AV1 ISOBMFF Mapping 2.4
+    https://aomediacodec.github.io/av1-isobmff/#sampleformat
+    Matroska/WebM
+    https://github.com/Matroska-Org/matroska-specification/blob/master/codec/av1.md
+*/
+static inline block_t * AV1_Unpack_Sample(block_t *p_block)
+{
+    /* Restore last size field if missing */
+    p_block = AV1_Unpack_Sample_ExpandSize(p_block);
+    /* Reinsert removed TU: See av1-isobmff 2.4 */
+    if(p_block &&
+       (p_block->p_buffer[0] & 0x81) == 0 && /* reserved flags */
+       (p_block->p_buffer[0] & 0x7A) != 0x12) /* no TEMPORAL_DELIMITER */
+    {
+        p_block = block_Realloc(p_block, 2, p_block->i_buffer);
+        if(p_block)
+        {
+            p_block->p_buffer[0] = 0x12;
+            p_block->p_buffer[1] = 0x00;
+        }
+    }
+    return p_block;
+}
+
+#endif