MediaOnDeck
浏览器内的音视频工具集。所有处理都在你的设备上完成 —— 文件不离开本机，不上传、不留存。
MediaOnDeck
A collection of media tools that run entirely in your browser. Everything is processed on your device — nothing is uploaded, nothing is stored.
Available tools
MP4 Analyzer
逐帧拆解 MP4 码流：盒子结构树、宏块 / CU 级 QP 热力图、运动矢量箭头、原始比特流十六进制跳转。
打开 →Unpack MP4 bitstreams frame by frame: box tree, macroblock/CU-level QP heatmap, motion vector arrows, and hex jump into the raw bitstream.
Open →Speech to Text
soon浏览器内语音识别，音频不出本机。
In-browser speech recognition — audio never leaves your device.
Text to Speech
soon本地合成语音，可导出音频。
Local speech synthesis with audio export.
Audio Analysis
soon频谱、响度、波形分析。
Spectrum, loudness and waveform analysis.
Why in-browser
Your video and audio files are processed on your device from start to finish.
No backend server means no queueing and no upload wait.
Every tool is free to use, with no account required.
Documentation
From opening a file to reading the QP heatmap: UI layout, shortcuts and common analysis workflows.
How it worksHow the pipeline works: ISOBMFF box parsing, NAL unit splitting, slice header decoding, QP and motion vector extraction.
Engineering notesReal problems hit while building this, and how each fix was proven: keyframe detection, 16-bit pixel shifts, GB-scale files in a 2 GB wasm heap, motion-vector ground truth.
FAQSupported codecs and containers, why some frames have no QP data, and the limits for 8K or very large files.
PrivacyExactly what stays local, what is never uploaded, plus notes on local storage and advertising cookies.
About MP4 Analyzer
MP4 Analyzer 是一个运行在浏览器里的 MP4 码流分析工具。它不做转码，也不做播放器， 而是把编码器写进文件里的东西逐层拆开给你看 —— 从最外层的 ISOBMFF 容器结构，一路下到单个编码块的量化参数与运动矢量。
它解决什么问题
调码率、查画质问题时，光看播放画面往往找不到原因。同样码率下画面忽好忽坏， 通常是因为编码器的码率分配策略在特定画面上失衡 —— 某个区域分到了过高的 QP（量化步长偏大， 细节被压掉），或者运动矢量异常。这些信息不会显示在播放器里，只会存在于码流本身。 MP4 Analyzer 把这些数据画出来，让"哪里画质被牺牲了"一眼可见。
能做什么
- 盒子树：递归解析
ftyp/moov/trak/stbl等完整层级，定位每个 sample 的字节偏移； - 帧列表：逐帧列出 size、PTS、DTS、偏移与 I / P / B 类型判定；
- CU / 宏块级 QP 热力图：按编码块着色显示量化参数分布，看出码率分配是否均衡；
- 运动矢量叠加：把 MV 画在帧图像上，观察运动估计的预测方向与幅度；
- 原始比特流：十六进制视图，可从任意字段跳转到对应的字节位置。
支持的格式
容器支持 MP4 / MOV / M4V 等 ISOBMFF 家族格式；视频编码支持 H.264 (AVC) 与 H.265 (HEVC)，HEVC 路径可提取真实的叶子 CU 尺寸与 QP。音频轨道会一并列出基本信息。 详细的编码支持边界见常见问题。
为什么不用装软件
传统码流分析工具（如 Elecard、CodecVisa）需要安装桌面软件，且多数要授权费。 这些工具的核心计算并不依赖特殊硬件，现代浏览器已经足够胜任 —— 于是有了这个不需要安装、不需要上传、不需要账号的版本。 你的文件从头到尾只在你自己的设备上被读取，断开网络也能继续用。
MP4 Analyzer is a bitstream inspection tool that runs in your browser. It is not a transcoder and not a player — instead it takes what the encoder wrote into the file and opens it up layer by layer, from the outermost ISOBMFF container structure all the way down to the quantization parameter and motion vectors of an individual coding block.
What problem it solves
When tuning bitrate or investigating quality complaints, watching the playback rarely tells you why. The same bitrate producing intermittent quality usually means the encoder's bitrate allocation is unbalanced on particular frames — some region received an unusually high QP (a coarser quantization step, flattening detail), or its motion vectors are abnormal. None of that appears in a player; it only exists in the bitstream. MP4 Analyzer draws that data out so it is immediately visible where quality was traded away.
What it does
- Box tree: recursively parses the full hierarchy of
ftyp/moov/trak/stbl, locating the byte offset of every sample; - Frame list: per-frame size, PTS, DTS, offset and I / P / B classification;
- CU / macroblock-level QP heatmap: colors each coding block by its quantization parameter so you can see whether bitrate allocation is balanced;
- Motion vector overlay: draws MVs over the frame image to inspect prediction direction and magnitude;
- Raw bitstream: a hex view you can jump into from any decoded field.
Supported formats
Containers cover the ISOBMFF family such as MP4 / MOV / M4V. Video codecs include H.264 (AVC) and H.265 (HEVC); the HEVC path can extract real leaf CU sizes and QP. Audio tracks are listed with their basic parameters. For the exact boundaries of codec support, see the FAQ.
Why nothing to install
Traditional bitstream analyzers such as Elecard or CodecVisa require installing desktop software, and most charge a license fee. Their core computation needs no special hardware, and a modern browser is more than sufficient — which is how a version that needs no installation, no upload and no account came about. Your file is read only on your own device, start to finish, and everything keeps working with the network disconnected.
需要较新版本的 Chrome、Edge 或 Safari。帧预览依赖浏览器内置的硬件解码器。
Please use a recent version of Chrome, Edge or Safari. Frame preview uses the browser's built-in hardware decoder.