FFmpeg 7.1 + cuframes input demuxer

Snapshot FFmpeg n7.1 (release tag) с применённым patch'ем для cuframes
input format. Используется как FFMPEG_REPO_OVERRIDE в NickM-27/FFmpeg-Builds
fork для статической сборки patched binary под Frigate (Debian 12 / glibc 2.36).

Apply changes:
  + libavformat/cuframesdec.c (новый — реализация демуксера)
  M libavformat/Makefile (CONFIG_CUFRAMES_DEMUXER target)
  M libavformat/allformats.c (extern declaration)
  M configure (--enable-libcuframes option + dep check)

Patch source: https://git.goldix.org/gx/cuframes (filter/ffmpeg-7.1-cuframes-demuxer.patch)

History сброшена (snapshot вместо fork) потому что upstream shallow clone
не позволял push в gitea. Полная история FFmpeg — на github.com/FFmpeg/FFmpeg n7.1.

libavcodec/parser.h

@@ -0,0 +1,58 @@
+/*
+ * AVCodecParser prototypes and definitions
+ * Copyright (c) 2003 Fabrice Bellard
+ * Copyright (c) 2003 Michael Niedermayer
+ *
+ * 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_PARSER_H
+#define AVCODEC_PARSER_H
+
+#include "avcodec.h"
+
+typedef struct ParseContext{
+    uint8_t *buffer;
+    int index;
+    int last_index;
+    unsigned int buffer_size;
+    uint32_t state;             ///< contains the last few bytes in MSB order
+    int frame_start_found;
+    int overread;               ///< the number of bytes which where irreversibly read from the next frame
+    int overread_index;         ///< the index into ParseContext.buffer of the overread bytes
+    uint64_t state64;           ///< contains the last 8 bytes in MSB order
+} ParseContext;
+
+#define END_NOT_FOUND (-100)
+
+/**
+ * Combine the (truncated) bitstream to a complete frame.
+ * @return -1 if no complete frame could be created,
+ *         AVERROR(ENOMEM) if there was a memory allocation error
+ */
+int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size);
+void ff_parse_close(AVCodecParserContext *s);
+
+/**
+ * Fetch timestamps for a specific byte within the current access unit.
+ * @param off byte position within the access unit
+ * @param remove Found timestamps will be removed if set to 1, kept if set to 0.
+ * @param fuzzy Only use found value if it is more informative than what we already have
+ */
+void ff_fetch_timestamp(AVCodecParserContext *s, int off, int remove, int fuzzy);
+
+#endif /* AVCODEC_PARSER_H */