From 4b5967b1fde15f0d7d677274f1ae353915e6854b Mon Sep 17 00:00:00 2001
From: Dennis Fink
Date: Fri, 8 May 2026 22:16:51 +0200
Subject: feat(core): expose frame-rate variables to presets

Add input_frame_rate, input_fps, and output_gop_size to the set of
variables available to preset files at source time.

input_frame_rate is the raw ffprobe fraction (e.g. 30000/1001).
input_fps rounds that fraction to the nearest integer via awk.
output_gop_size is derived as roughly five seconds of video (input_fps *
5), capped at 300 frames.

The ffprobe invocation is extended to request r_frame_rate alongside the
existing codec_name and pix_fmt entries; a missing frame rate is now
treated as a hard error. Dry-run and verbose output are updated to
display the new values. Documentation (header comment, --help text, man
page, README) is updated accordingly.
---
 README.md | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'README.md')

diff --git a/README.md b/README.md
index bc9945d..95ffb9b 100644
--- a/README.md
+++ b/README.md
@@ -85,6 +85,9 @@ The following variables are available to presets at source time:
 | `input_codec` | Video codec of the input file (e.g. `h264`, `hevc`) |
 | `input_pixel_format` | Pixel format of the input after `yuvj*` normalisation (e.g. `yuv420p`) |
 | `output_pixel_format` | Recommended output pixel format, derived from the input to preserve chroma subsampling and bit depth |
+| `input_frame_rate` | Raw frame rate fraction of the input file as reported by `ffprobe` (e.g. `30000/1001`, `25/1`) |
+| `input_fps` | `input_frame_rate` rounded to the nearest integer (e.g. `30`, `25`, `60`) |
+| `output_gop_size` | Recommended GOP size derived from `input_fps` (≈ 5 s of video, capped at 300 frames) |
 
 Before the preset's `ffargs` are appended, the script always passes
 these base arguments to `ffmpeg`:
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