hevc: split bitstream unescaping to a separate file

It will be useful in the QSV HEVC encoder.

1 files changed, 129 insertions, 0 deletions

diff --git a/libavcodec/hevc_parse.c b/libavcodec/hevc_parse.c
new file mode 100644
index 0000000..32a440b
--- /dev/null
+++ b/libavcodec/hevc_parse.c
@@ -0,0 +1,129 @@
+/*
+ * HEVC common code
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <string.h>
+
+#include "config.h"
+
+#include "libavutil/intreadwrite.h"
+#include "libavutil/mem.h"
+
+#include "hevc.h"
+
+/* FIXME: This is adapted from ff_h264_decode_nal, avoiding duplication
+ * between these functions would be nice. */
+int ff_hevc_extract_rbsp(const uint8_t *src, int length,
+                         HEVCNAL *nal)
+{
+    int i, si, di;
+    uint8_t *dst;
+
+#define STARTCODE_TEST                                                  \
+        if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) {     \
+            if (src[i + 2] != 3) {                                      \
+                /* startcode, so we must be past the end */             \
+                length = i;                                             \
+            }                                                           \
+            break;                                                      \
+        }
+#if HAVE_FAST_UNALIGNED
+#define FIND_FIRST_ZERO                                                 \
+        if (i > 0 && !src[i])                                           \
+            i--;                                                        \
+        while (src[i])                                                  \
+            i++
+#if HAVE_FAST_64BIT
+    for (i = 0; i + 1 < length; i += 9) {
+        if (!((~AV_RN64A(src + i) &
+               (AV_RN64A(src + i) - 0x0100010001000101ULL)) &
+              0x8000800080008080ULL))
+            continue;
+        FIND_FIRST_ZERO;
+        STARTCODE_TEST;
+        i -= 7;
+    }
+#else
+    for (i = 0; i + 1 < length; i += 5) {
+        if (!((~AV_RN32A(src + i) &
+               (AV_RN32A(src + i) - 0x01000101U)) &
+              0x80008080U))
+            continue;
+        FIND_FIRST_ZERO;
+        STARTCODE_TEST;
+        i -= 3;
+    }
+#endif /* HAVE_FAST_64BIT */
+#else
+    for (i = 0; i + 1 < length; i += 2) {
+        if (src[i])
+            continue;
+        if (i > 0 && src[i - 1] == 0)
+            i--;
+        STARTCODE_TEST;
+    }
+#endif /* HAVE_FAST_UNALIGNED */
+
+    if (i >= length - 1) { // no escaped 0
+        nal->data     =
+        nal->raw_data = src;
+        nal->size     =
+        nal->raw_size = length;
+        return length;
+    }
+
+    av_fast_malloc(&nal->rbsp_buffer, &nal->rbsp_buffer_size,
+                   length + FF_INPUT_BUFFER_PADDING_SIZE);
+    if (!nal->rbsp_buffer)
+        return AVERROR(ENOMEM);
+
+    dst = nal->rbsp_buffer;
+
+    memcpy(dst, src, i);
+    si = di = i;
+    while (si + 2 < length) {
+        // remove escapes (very rare 1:2^22)
+        if (src[si + 2] > 3) {
+            dst[di++] = src[si++];
+            dst[di++] = src[si++];
+        } else if (src[si] == 0 && src[si + 1] == 0) {
+            if (src[si + 2] == 3) { // escape
+                dst[di++] = 0;
+                dst[di++] = 0;
+                si       += 3;
+
+                continue;
+            } else // next start code
+                goto nsc;
+        }
+
+        dst[di++] = src[si++];
+    }
+    while (si < length)
+        dst[di++] = src[si++];
+
+nsc:
+    memset(dst + di, 0, FF_INPUT_BUFFER_PADDING_SIZE);
+
+    nal->data = dst;
+    nal->size = di;
+    nal->raw_data = src;
+    nal->raw_size = si;
+    return si;
+}