ナレッジハブ・技術ガイド
WebAssembly動画変換・形式コンバーター（FFmpeg）
WebAssembly動画変換・形式コンバーター（FFmpeg）
本ツールは100%クライアントサイド（ブラウザ内）で動作します。写真、動画、音声、PDFファイルが外部サーバーにアップロードされることは一切なく、お使いの端末のメモリ内で安全に処理されます。
コアアーキテクチャ & 計算式
Transcode = Demux(Container) ➔ Decode(Video/Audio) ➔ Encode(New Codec) ➔ Mux(New Container)
A video file is just a container (like a box). Inside the box is a video stream and an audio stream. Conversion requires opening the box, translating the streams mathematically, and putting them into a new box.
ベストプラクティスとガイドライン
- Mind the GIF Size: Converting a 1080p video directly into a GIF will create a massive, unusable file. Always reduce the frame rate (e.g., to 15 FPS) and scale the resolution down (e.g., 480px width) before encoding to GIF.
- Extract Audio for Podcasts: If you recorded a video interview but only need the audio, do not re encode the video. Simply use this tool to demux the MP4 and extract the pristine, untouched AAC or MP3 audio track instantly.
- Understand Codec Licensing: Certain highly efficient codecs (like HEVC/H.265) require expensive hardware licensing and cannot be natively encoded by open source web tools. Stick to universally supported formats like H.264 or VP9.
よくある質問 (FAQ)
Why is the conversion process slow?
Video encoding requires massive mathematical computation. While FFmpeg.wasm is incredibly powerful, running it inside a browser sandbox is naturally slower than running a native desktop application.
Will converting a video improve its quality?
No. Conversion is almost always a 'lossy' process. You can convert a low quality 480p video into a 4K file, but the visual data will not magically improve; the file will just get pointlessly large.
Does this tool support massive 4K files?
WebAssembly has strict memory limitations (usually 2GB to 4GB of RAM per tab). Attempting to transcode a massive 10GB 4K movie file will likely crash your browser. Use this tool for short clips.