Insert Edit and VBR File Re-wrapping

Whether it is regarding Cinedeck recorders or cineXinsert, there are a lot of questions about the inner workings of Cinedeck’s true, file-based insert editing. In particular, the reasons for re-wrapping VBR codecs like Apple ProRes in order to allow inserts into a flat, final file.

Cinedeck’s insert edit uses some interesting techniques to locate and replace content in your files. Part of that science is knowing that each frame is the same size. So a CBR DNx file presents no issues, while a VBR ProRes recording does present some limitations. So, we re-wrap the ProRes essence; which is essentially a file-copy process of pouring the ProRes out of one container into another while simultaneously adding some amount of Zeros to each frame to make them all the same size. Once the frames are uniform, the Cinedeck application can more easily access and rewrite specific frames. When finished, the file can again be re-wrapped back to VBR by pouring the essence into a new wrapper while simultaneously removing the unneeded Zeros from each frame.

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That is really all there is to it… Put in some filler to create equal-sized space for each frame and allow insert editing and then optionally, remove the filler to shrink the file back down a bit. The difference in ProRes file size between VBR and CBR is on average 10% to 30% but that can vary greatly between files and the difference can be minimal for complex content.

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