I want to take a live HD-SDI signal being captured by a capture card and encode it in real time to X.264.

What happens when the input resolution suddenly changes? eg, from HD SDI 1080/50i to HD SDI 720/59p, etc.

Does the encoder handle that gracefully? Or would there be some artifacts/disturbance in the output? (or worse?)

  • Haven't come across that scenario but you could apply a scale, deinterlace and fps filter so that libx264 is processing frames with the same properties.
    – Gyan
    Feb 9, 2016 at 5:20
  • Thanks for the comment. I don't think that will work well. The encoded content written to disk must later be played back out an HD-SDI card at the original resolution and frame rate (of course at a lower quality). Modifying the frame rate on encode will introduce some unacceptable artifacts.
    – Danny
    Feb 9, 2016 at 9:40

1 Answer 1


FFmpeg will automatically insert scale filter to rescale to first resolution when it encounters input resolution changes. Obviously this only applies when encoding.

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