Transcode

Transcode, an option under the Settings pulldown right next to the Proxy settings option, is a type of full resolution 1:1 Proxy . The process of transcoding works directly from the resource; it is independent of the timeline. All of the loaded asset media will be converted, that is, rendered in the selected format and loaded onto the timeline. Menu choices besides the usual File Format and File Type include: Tag suffix (to add to media filename), Remove originals from project, Into Nested Proxy directory (an option to have the file saved here instead of the location of the original media), and Beep on done volume.

The settings of the project have an effect on the outcome, for example the dimensions are taken into account. The resulting files are also larger than if they were created directly with ffmpeg. Transcode works for videos with or without audio and even single frame files, like png's. If you have a video file that also contains audio, and you convert only the video, the original audio will stay on the timeline if do not check Remove originals from project. Or vice versa if audio converted and not video. Multiple stream media will only transcode the first stream (this would be like the TV channel recordings in the United States). You will get an error message if you already have a transcoded file in the selected format with the same suffix name and try to transcode it again with a different selection made – you will have to delete that file first. An example would be an already converted file that has both video and audio and now you request video only.

The BIGGEST gain from using this is if you have media that is not seekable , that is, you can play it from the beginning but can not move to another spot and have the audio or video play correctly. A video file with no keyframes makes seeking next to impossible, but then a Transcode generally adds these keyframes. This is particularly useful for the mkv container, which often has seek problems. For more details on mkv container see A.2.1.3

Another important function of Transcode is being able to convert the project's media into a high-quality mezzanine codec (sometimes also called intermediate codec ), which makes timeline work lighter and more efficient. In fact such codecs (ffv1, ProRes, DNxHD, OpenEXR, huffyuv, etc) are generally little or not at all compressed; the type of compression is intraframe –more suitable for editing, and the image quality (4:2:2 up; 10-bit color up; floating point; etc) is suitable for Color Correction, Chroma Key and Rotoscoping. The use of mezzanine codecs leads to very large files, so you need to make sure you have enough storage space.

NOTE:

CINELERRA-GG cannot do remuxing without transcoding. For remuxing only, use ffmpeg as shown in the following script. First move to the folder containing the files to be remuxed; the script takes all video files of a certain extension (in the following example avi) from the folder and its subfolders and makes a remux in a new container (in this example mkv) inside the new folder remux. The internal codec will remain the original one. Here is an example script:

	for f in $(find . -name '*.avi'); do ffmpeg -i "$f" -c:v copy -c:a copy "remux/{f%.*}.mkv "; done