I’ve used Shotcut for one project 5 years ago and now I wanted to assemble a few recordings to a complete video and edit it a bit. So I installed the latest version and just started with it.
I dropped my smartphone video recordings into the playlist panel and was immediately asked to convert the files to a format more suitable for editing. I did, now I have duplicate files of everything, in the playlist and on disk.
But why did I do this? What’s the purpose? And which of the files in my playlist panel should I use now, the original or the converted files? I’m clueless. I totally don’t understand the point of that behaviour. A web search hasn’t brought up any explanation. Am I the first user to see this feature?
PS: The German translation is unusable. Where the dialog title in English is “dropped files” (which makes sense after dragging and dropping the files), the German version translates back as “lost files”. That was very suspicious, why would the application lose files right at the start? Switching to English clarified things. I’ll stay with English because I expect more of these confusing errors.
The Convert dialog window tells you why. The tool is giving you advice and trying to help you avoid a bad result. You have the option to ignore it and click Cancel. Common sense is that if you were given the advice, you accepted it and converted, you should use the use the converted files.
Okay. My source files are regular smartphone recordings in MP4 1080p30, nothing special. Guess I don’t need that. It was confusing at first because the dialog suggested me to do it even though I now understand that I absolutely don’t need to. The dialog could be smarter here and only offer it when problematic files are added.
It is smart and only appears on potentially problematic files. Smart phones record with variable frame rate. However, variable can be anywhere from very little variability to very much. That it does not know, annd I don’t even know what it is an unsafe threshold.
It turns out that “MP4” doesn’t actually say very much about how the video is encoded. MP4 is only a “container,” in which various elements of a video (sound, image sequence, subtitles, metadata) can be collected … and if I recall correctly, only the metadata format is dictacted by the container. The others can be any number of different encoding formats (mpeg, h.264, wav, FLAC, mp3 …) - and within any given encoding format, there are additional sublevels of encoding (bit depth, bit rate, pixels encoded as RGB, YUV, color encoded as 4:4:4 or 4:2:2 or so on …). Honestly, the complexity that goes into compressing video down to a size that can be more easily and rapidly stored and transmitted is astonishing, and it is all hidden behind that innocuous “.mp4”!
Even more astonishing, Shotcut and other NLV editors handle all of this complexity seamlessly and in real-time, even mixing together videos which (regardless of the container) may each have very different combinations of the various options noted above. The one thing that makes it extremely difficult to apply effects and merge videos in a real-time process is if any of the videos use variable bit rate. Note that different bit rates for each video is okay, but when a single video may be running at 2k bits at one moment and 20k bits the next, it is … a bear. It is one thing to decode this in real-time to play the video, but mixing it in with other videos and effects and more … just too much.
Fortunately, Shotcut makes it easy: when it detects a video that is encoded in a way that will make it difficult to process in real-time and with the effects one expects, it alerts you to the need to convert them into a fixed-bit-rate form that will assure a good result when editing.