fix(video): track latency timestamps by encoded frame

[qiin2333]

改了啥呀，杂鱼

• 新增一个固定 256 槽的 frame timestamp ring，用提交帧号保存 capture timestamp。
• AVCodec 按返回 packet 的 PTS 回查 timestamp。
• NVENC/AMF 按编码器实际返回的 encoded_frame.frame_index 回查 timestamp。
• AMF pipeline lag / 分片输出时，不再把“当前提交帧”的 timestamp 误绑到“上一帧输出”上。

为啥这样改

之前 host processing latency 的 packet timestamp 直接来自当前 encode 调用的 frame_timestamp。当编码器输出落后于提交帧时，尤其 AMF 每帧分片/流水线输出场景，会低估完整帧从 capture 到 packet 出队的时间。

这个实现只做 O(1) 数组读写，没有 map、堆分配、新计时点或额外日志，默认路径上的性能开销保持很低。

验证

• git diff --check -- src/video.cpp
• 本机 ninja -C build CMakeFiles/sunshine.dir/src/video.cpp.obj 被 MSYS GCC 前端崩溃阻塞：cc1plus.exe --version 直接退出 -1073741511，最小 C++ 文件编译也同样静默失败，无法作为该 diff 的编译诊断。

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• src/video.cpp

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src/**/*.{cpp,c,h}

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src/**/*.{cpp,c,h}: Sunshine 核心 C++ 源码，自托管游戏串流服务器。审查要点：内存安全、 线程安全、RAII 资源管理、安全漏洞。注意预处理宏控制的平台相关代码。

Files:

• src/video.cpp

🔇 Additional comments (7)

src/video.cpp (7)

7-13: LGTM!

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Summary by CodeRabbit

Bug Fixes

• 修复视频编码过程中的时间戳错配问题，确保编码器输出的视频帧时间戳准确性和同步一致性。

Walkthrough

采用固定大小环形缓冲区（256 槽）存储帧号与采集时间戳的映射，在 AVCodec、NVENC、AMF 三种编码器会话中集成该缓冲，于帧提交时记录时间戳、输出时根据编码器返回的帧索引回查对应时间戳，替代之前的直接时间戳传递或基于 pts 匹配的逻辑。

Changes

编码器时间戳追踪与环形缓冲集成

Layer / File(s)	Summary
Ring buffer data structure and dependencies src/video.cpp	定义 frame_timestamp_ring_t 结构，以 256 槽数组存储帧号与可选时间戳，并提供 store() 和 lookup() 方法处理模运算包裹。新增相关 C++ 标准库依赖头文件。
AVCodec session timestamp tracking and lookup src/video.cpp	在 avcodec_encode_session_t 中新增 frame_timestamps 成员，encode_avcodec() 在帧提交时记录时间戳，输出包生成时按 pts 回查对应时间戳。同时处理移动赋值时的缓冲转移。
NVENC session with track and resolve methods src/video.cpp	在 nvenc_encode_session_t 中新增 track_frame_timestamp() 和 resolve_frame_timestamp() 包装方法及 frame_timestamps 成员，encode_nvenc() 帧提交时调用 track_frame_timestamp()，输出时按编码器返回的帧号回查时间戳。
AMF session with track and resolve methods src/video.cpp	在 amf_encode_session_t 中新增与 NVENC 同构的 track_frame_timestamp() 和 resolve_frame_timestamp() 方法及 frame_timestamps 成员，encode_amf() 帧提交时记录，输出时按帧索引回查。

🎯 4 (Complex) | ⏱️ ~45 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 7.69% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	PR标题"fix(video): track latency timestamps by encoded frame"清晰、准确地概括了主要改动——通过编码帧跟踪延迟时间戳，与文件改动内容高度相关。
Description check	✅ Passed	PR描述详细说明了改动内容（256槽frame timestamp ring、AVCodec/NVENC/AMF回查逻辑）、改动原因（解决编码器输出滞后导致的时间戳错配）及性能考量，与变更集紧密相关。
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/accurate-host-latency

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 Infer (1.2.0)

src/video.cpp

src/video.cpp:16:10: fatal error: 'boost/pointer_cast.hpp' file not found
16 | #include <boost/pointer_cast.hpp>
| ^~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
src/video.cpp:100:7-14: ERROR translating statement 'ReturnStmt'
Aborting translation of method 'video::anonymous_namespace_src_video.cpp::allow_encoder_probing' in file 'src/video.cpp': "Assert_failure src/clang/cAst_utils.ml:249:53"
Uncaught Internal Error: "Assert_failure src/clang/cAst_utils.ml:249:53"
Error backtrace:
Raised at ClangFrontend__CAst_utils.get_decl_from_typ_ptr in file "src/clang/cAst_utils.ml", line 249, characters 53-65
Called from ClangFrontend__CTrans.CTrans_funct.get_destructor_decl_ref in file "src/clang/cTrans.ml", line 658, characters 12-59
Called from ClangFrontend__CTrans.CTrans_funct.destructor_calls.(fun) in file "src/clang/cTrans.ml", line 2048, characters 12-69
Called from Base__List.rev_filter_map.loop in file "src/list.ml", line 944, characters 13-17
Called from Base__List.filt

... [truncated 2200 characters] ...

clang/cTrans.ml", line 4784, characters 10-1023
Called from ClangFrontend__CTrans.CTrans_funct.instruction in file "src/clang/cTrans.ml" (inlined), line 4765, characters 38-71
Called from ClangFrontend__CTrans.CTrans_funct.exec_with_node_creation in file "src/clang/cTrans.ml" (inlined), line 104, characters 20-38
Called from ClangFrontend__CTrans.CTrans_funct.get_clang_stmt_trans in file "src/clang/cTrans.ml" (inlined), line 5395, characters 4-69
Called from ClangFrontend__CTrans.CTrans_funct.get_custom_stmt_trans in file "src/clang/cTrans.ml", line 5401, characters 8-55
Called from ClangFrontend__CTrans.CTrans_funct.exec_trans_instrs.exec_trans_instrs_rev in file "src/clang/cTrans.ml" (inlined), line 5365, characters 28-54
Called from ClangFrontend__CTrans.CTrans_funct.exec_trans_instrs i

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