RCompr把 Canon Cinema RAW Light 縮小，
輸出仍然是 CRM。
Shrink Canon Cinema RAW Light.
It stays CRM.
RCompr 在 .CRM 檔案內的小波係數層級重新量化，容器、metadata、時間碼與音訊原樣保留。輸出檔在 Canon Cinema RAW Development 與 DaVinci Resolve 裡和原檔一樣打開、一樣調色。
RCompr re-quantizes at the wavelet-coefficient level inside .CRM files and leaves the container, metadata, timecode and audio untouched. The output opens and grades like the original in Canon Cinema RAW Development and DaVinci Resolve.
為什麼需要
Why
EOS R6 V 的 6K Cinema RAW Light，每一幀平均 13.56 MB。
6K Cinema RAW Light from the EOS R6 V averages 13.56 MB per frame.
6984 × 4656 編碼尺寸下的原生碼率（4 支實測片段都是 3.335）
native rate at the 6984 × 4656 coding size (3.335 on all 4 measured clips)
一支 1059 幀的片段。以 24 fps 計，每分鐘約 19.5 GB
for one 1059-frame clip. At 24 fps that is about 19.5 GB per minute
不解成影像再重編，直接改係數；Lossless 時輸出與原檔逐位元組相同
No decode-and-re-encode; the coefficients are changed in place. At Lossless the output is byte-identical to the source
轉成 XF-AVC 或 ProRes 會把白平衡、ISO 與曝光烤進去，RAW 的調色餘裕就沒了。RCompr 變小之後仍是 CRM：Canon 自己的軟體與 Resolve 都把它當一般的 Cinema RAW Light 片段處理，metadata、時間碼與音訊都在。
Converting to XF-AVC or ProRes bakes in white balance, ISO and exposure, and the RAW latitude is gone. After RCompr the file is still CRM: Canon's own software and Resolve treat it as an ordinary Cinema RAW Light clip, with metadata, timecode and audio intact.
怎麼壓、壓多少
How it compresses, and how much
CRM 的影像是 CRX 小波編碼。RCompr 自己解出係數、調整每個子頻帶的量化步階、再用與相機相同的熵編碼寫回去。熵編碼是確定性的：係數不變時，重寫的位元組與原檔完全相同，這是我們能確認「只動了該動的地方」的依據。
CRM images are CRX wavelet-coded. RCompr decodes the coefficients itself, adjusts the quantization step of each sub-band and writes them back with the same entropy coder the camera uses. That coder is deterministic: with unchanged coefficients the rewritten bytes match the original exactly, which is how we know only the intended parts change.
| 檔位 | Preset | bpp | 影像資料大小 | Image data size | 實測（R6 V，24 幀） | Measured (R6 V, 24 frames) |
|---|---|---|---|---|---|---|
| Lossless | = 原檔source | 0% | 係數不變；R6 V 的檔沒有填充可省，大小不變，輸出逐位元組相同 | Coefficients unchanged; R6 V files have no padding to drop, so size is unchanged and the output is byte-identical | ||
| Light | × 0.75 | ≈ −25% | 每幀 −25.3% 到 −26.0%；誤差 0.51 到 0.57σ | −25.3% to −26.0% per frame; error 0.51 to 0.57σ | ||
| Medium | × 0.55 | ≈ −45% | 每幀 −45.2% 到 −45.3%；誤差 0.70 到 0.73σ | −45.2% to −45.3% per frame; error 0.70 to 0.73σ | ||
| Strong | × 0.35 | ≈ −65% | 每幀 −65.0% 到 −65.1%；誤差 0.93 到 1.00σ | −65.0% to −65.1% per frame; error 0.93 to 1.00σ |
σ＝壓縮造成的誤差是該幀本身雜訊的幾倍，在 14-bit Bayer 資料上計算。1σ 以下表示誤差淹沒在雜訊裡。
σ = the compression error as a multiple of the frame's own noise, computed on the 14-bit Bayer data. Below 1σ the error is buried in the noise.
播放器與預覽
Player and preview
內建播放器直接解 CRM 低頻顯示（灰世界白平衡的估計顯影，給看構圖、對焦與動態用，不是 Canon 的色彩）；壓縮前後可並排比對。
The built-in player decodes the CRM directly (an estimated development with grey-world white balance, for framing, focus and motion, not Canon's colour); compare before and after side by side.
也能轉 H.265
H.265 too
需要代理檔時可輸出 10-bit HEVC（.mp4），6K 或 4K。
For proxies, export 10-bit HEVC (.mp4) at 6K or 4K.
驗證過的機身
Verified cameras
EOS R6 V（Cinema RAW Light，CRM 0002）。其他機身的 CRM 歡迎用測試版試，並用 app 內的意見回饋告訴我們結果。
EOS R6 V (Cinema RAW Light, CRM 0002). Try CRM from other bodies with the beta and tell us the result through the in-app feedback.
怎麼用
How to use it
全部在你的 Mac 上完成，檔案不會上傳到任何地方。
Everything runs on your Mac; nothing is uploaded anywhere.
安裝
Install
下載 RCompr.dmg，打開後把 RCompr 拖進「應用程式」。已經過 Apple 公證，直接雙擊就能開。
Download RCompr.dmg, open it and drag RCompr into Applications. It is notarized by Apple, so it opens with a double-click.
加入片段
Add clips
把 .CRM 檔（或整個資料夾）拖進視窗。清單會列出尺寸、幀數、大小與原生 bpp。
Drag .CRM files (or whole folders) into the window. The list shows size, frame count, file size and native bpp.
選檔位，看預覽
Pick a preset, check the preview
RAW 模式選 Lossless／Light／Medium／Strong 或拉滑桿；點縮圖進預覽比對。
In RAW mode choose Lossless / Light / Medium / Strong or drag the slider; click a thumbnail to compare in the preview.
選輸出位置
Choose where output goes
子資料夾、原檔旁（可自訂檔名格式）或指定資料夾。可勾選「完成後把原檔移到垃圾桶」。
A subfolder, beside the original (with a custom name format) or a fixed folder. Optionally move originals to the Trash when done.
開始
Start
按「開始壓縮」。進度、fps 與剩餘時間即時顯示；完成後清單顯示省了多少。
Press Start. Progress, fps and time remaining update live; when done the list shows how much you saved.
監看資料夾（選用）
Watch folders (optional)
指定幾個資料夾，新片段寫入穩定後自動壓縮，可登入時自動啟動、在選單列顯示狀態。
Point it at folders; new clips are compressed automatically once they stop changing. It can launch at login and shows status in the menu bar.
測試版的規則：每台 Mac 從第一次按「開始」起 30 天；到期後 app 還能打開看片段，但不能壓縮、轉檔與監看，到同一個網址拿新版再按一次開始就好。只處理拍攝時間在現在以前的片段。有想法請用「輔助說明」選單的「意見回饋…」告訴我們。
Beta rules: each Mac gets 30 days from the first time you press Start; after that the app still opens and shows clips but will not compress, convert or watch until you download the new version from the same address and press Start again. Only clips recorded before now are processed. Send ideas through Help → Send Feedback.