+ H_1080P = 1080,
+ H_4K = 2160
+}
+
+/**
+ * Bitrate targets for different resolutions, at VideoTranscodingFPS.AVERAGE.
+ *
+ * Sources for individual quality levels:
+ * Google Live Encoder: https://support.google.com/youtube/answer/2853702?hl=en
+ * YouTube Video Info: youtube-dl --list-formats, with sample videos
+ */
+function getBaseBitrate (resolution: VideoResolution) {
+ switch (resolution) {
+ case VideoResolution.H_NOVIDEO:
+ // audio-only
+ return 64 * 1000
+
+ case VideoResolution.H_240P:
+ // quality according to Google Live Encoder: 300 - 700 Kbps
+ // Quality according to YouTube Video Info: 285 Kbps
+ return 320 * 1000
+
+ case VideoResolution.H_360P:
+ // quality according to Google Live Encoder: 400 - 1,000 Kbps
+ // Quality according to YouTube Video Info: 700 Kbps
+ return 780 * 1000
+
+ case VideoResolution.H_480P:
+ // quality according to Google Live Encoder: 500 - 2,000 Kbps
+ // Quality according to YouTube Video Info: 1300 Kbps
+ return 1500 * 1000
+
+ case VideoResolution.H_720P:
+ // quality according to Google Live Encoder: 1,500 - 4,000 Kbps
+ // Quality according to YouTube Video Info: 2680 Kbps
+ return 2800 * 1000
+
+ case VideoResolution.H_1080P:
+ // quality according to Google Live Encoder: 3000 - 6000 Kbps
+ // Quality according to YouTube Video Info: 5081 Kbps
+ return 5200 * 1000
+
+ case VideoResolution.H_4K: // fallthrough
+ default:
+ // quality according to Google Live Encoder: 13000 - 34000 Kbps
+ return 22000 * 1000
+ }
+}
+
+/**
+ * Calculate the target bitrate based on video resolution and FPS.
+ *
+ * The calculation is based on two values:
+ * Bitrate at VideoTranscodingFPS.AVERAGE is always the same as
+ * getBaseBitrate(). Bitrate at VideoTranscodingFPS.MAX is always
+ * getBaseBitrate() * 1.4. All other values are calculated linearly
+ * between these two points.
+ */
+export function getTargetBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
+ const baseBitrate = getBaseBitrate(resolution)
+ // The maximum bitrate, used when fps === VideoTranscodingFPS.MAX
+ // Based on numbers from Youtube, 60 fps bitrate divided by 30 fps bitrate:
+ // 720p: 2600 / 1750 = 1.49
+ // 1080p: 4400 / 3300 = 1.33
+ const maxBitrate = baseBitrate * 1.4
+ const maxBitrateDifference = maxBitrate - baseBitrate
+ const maxFpsDifference = fpsTranscodingConstants.MAX - fpsTranscodingConstants.AVERAGE
+ // For 1080p video with default settings, this results in the following formula:
+ // 3300 + (x - 30) * (1320/30)
+ // Example outputs:
+ // 1080p10: 2420 kbps, 1080p30: 3300 kbps, 1080p60: 4620 kbps
+ // 720p10: 1283 kbps, 720p30: 1750 kbps, 720p60: 2450 kbps
+ return baseBitrate + (fps - fpsTranscodingConstants.AVERAGE) * (maxBitrateDifference / maxFpsDifference)
+}
+
+/**
+ * The maximum bitrate we expect to see on a transcoded video in bytes per second.
+ */
+export function getMaxBitrate (resolution: VideoResolution, fps: number, fpsTranscodingConstants: VideoTranscodingFPS) {
+ return getTargetBitrate(resolution, fps, fpsTranscodingConstants) * 2