Init commit

server/core/helpers/ffmpeg/framerate.ts

@@ -0,0 +1,93 @@
+import { VideoResolution } from '@peertube/peertube-models'
+import { CONFIG } from '@server/initializers/config.js'
+import { logger } from '../logger.js'
+
+export function computeOutputFPS (options: {
+  inputFPS: number
+  isOriginResolution: boolean
+  resolution: number
+  type: 'vod' | 'live'
+}) {
+  const { resolution, isOriginResolution, type } = options
+
+  if (resolution === VideoResolution.H_NOVIDEO) return 0
+
+  const settings = type === 'vod'
+    ? buildTranscodingFPSOptions(CONFIG.TRANSCODING.FPS.MAX)
+    : buildTranscodingFPSOptions(CONFIG.LIVE.TRANSCODING.FPS.MAX)
+
+  let fps = options.inputFPS
+
+  if (
+    // On small/medium transcoded resolutions, limit FPS
+    !isOriginResolution &&
+    resolution !== undefined &&
+    resolution < settings.KEEP_ORIGIN_FPS_RESOLUTION_MIN &&
+    fps > settings.AVERAGE
+  ) {
+    // Get closest standard framerate by modulo: downsampling has to be done to a divisor of the nominal fps value
+    fps = getClosestFramerate({ fps, settings, type: 'STANDARD' })
+  }
+
+  if (fps < settings.HARD_MIN) {
+    throw new Error(`Cannot compute FPS because ${fps} is lower than our minimum value ${settings.HARD_MIN}`)
+  }
+
+  // Cap min FPS
+  fps = Math.max(fps, settings.TRANSCODED_MIN)
+
+  // Cap max FPS for non-origin video file
+  if (!isOriginResolution && fps > settings.TRANSCODED_MAX) {
+    fps = getClosestFramerate({ fps, settings, type: 'HD_STANDARD' })
+  }
+
+  logger.debug(`Computed output FPS ${fps} for resolution ${resolution}p`, { options, settings })
+
+  return fps
+}
+
+// ---------------------------------------------------------------------------
+// Private
+// ---------------------------------------------------------------------------
+
+function buildTranscodingFPSOptions (maxFPS: number) {
+  const STANDARD = [ 24, 25, 30 ].filter(v => v <= maxFPS)
+  if (STANDARD.length === 0) STANDARD.push(maxFPS)
+
+  const HD_STANDARD = [ 50, 60, maxFPS ].filter(v => v <= maxFPS)
+
+  return {
+    HARD_MIN: 0.1,
+
+    TRANSCODED_MIN: 1,
+
+    TRANSCODED_MAX: maxFPS,
+
+    STANDARD,
+    HD_STANDARD,
+
+    AVERAGE: Math.min(30, maxFPS),
+
+    KEEP_ORIGIN_FPS_RESOLUTION_MIN: 720 // We keep the original FPS on high resolutions (720 minimum)
+  }
+}
+
+function getClosestFramerate (options: {
+  fps: number
+  settings: ReturnType<typeof buildTranscodingFPSOptions>
+  type: Extract<keyof ReturnType<typeof buildTranscodingFPSOptions>, 'HD_STANDARD' | 'STANDARD'>
+}) {
+  const { fps, settings, type } = options
+
+  const copy = [ ...settings[type] ]
+
+  // Biggest FPS first
+  const descSorted = copy.sort((a, b) => b - a)
+  // Find biggest FPS that can be divided by input FPS
+  const found = descSorted.find(e => fps % e === 0)
+
+  if (found) return found
+
+  // Approximation to the best result
+  return copy.sort((a, b) => fps % a - fps % b)[0]
+}