Realtime (frame dropping)

This option affects playback and controls two things:

  1. when ON: drop some video frames to try to keep the audio continuous and keep the video running near real-time
    This can make the video to appear choppy or slower frame rate than expected when it is on. Even when this is on it is possible that video processing is so intense that audio becomes choppy as well because Shotcut will not drop video frames indefinitely. In fact, currently it will only drop 5 consecutively (subject to change). Turn this off if you want to see every video frame regardless of how slow it goes or choppy the audio becomes.

  2. when OFF: use multiple threads for image processing (filters, transitions, and track blending/compositing) - except on 32-bit versions. Turn this setting off if you want to see if multiple threads can reduce some choppy playback or lag.

    • When this is option is off it turns on the same thing as Export > Advanced > Video > Parallel processing.
    • Shotcut will use up to 4 background threads to render 4 video frames at the same time.
    • Sometimes, this is the cause of a malformed image, which should be reported so it can be debugged.
    • Multiple frame threads does not apply to 32-bit versions because they can only access 3 GB RAM, which is already tight, and multiple image process threads consume much more memory. You can still use this to disable the frame-dropping on 32-bit.
    • This is in addition to image slice-threaded processing used in some effects. The number of these threads is typically the same as the number of CPU threads. These threads do not consume nearly as much memory.
    • The rule for the number of frame threads:
# CPU threads # Shotcut threads
> 4 4
4 3
3 2
2 1
1 1