Improve target bitrate calculation

1 files changed, 86 insertions, 0 deletions

diff --git a/shared/core-utils/videos/bitrate.ts b/shared/core-utils/videos/bitrate.ts
new file mode 100644
index 000000000..3d4e47906
--- /dev/null
+++ b/shared/core-utils/videos/bitrate.ts
@@ -0,0 +1,86 @@
+import { VideoResolution } from "@shared/models"
+
+type BitPerPixel = { [ id in VideoResolution ]: number }
+
+// https://bitmovin.com/video-bitrate-streaming-hls-dash/
+
+const averageBitPerPixel: BitPerPixel = {
+  [VideoResolution.H_NOVIDEO]: 0,
+  [VideoResolution.H_240P]: 0.17,
+  [VideoResolution.H_360P]: 0.15,
+  [VideoResolution.H_480P]: 0.12,
+  [VideoResolution.H_720P]: 0.11,
+  [VideoResolution.H_1080P]: 0.10,
+  [VideoResolution.H_1440P]: 0.09,
+  [VideoResolution.H_4K]: 0.08
+}
+
+const maxBitPerPixel: BitPerPixel = {
+  [VideoResolution.H_NOVIDEO]: 0,
+  [VideoResolution.H_240P]: 0.29,
+  [VideoResolution.H_360P]: 0.26,
+  [VideoResolution.H_480P]: 0.22,
+  [VideoResolution.H_720P]: 0.19,
+  [VideoResolution.H_1080P]: 0.17,
+  [VideoResolution.H_1440P]: 0.16,
+  [VideoResolution.H_4K]: 0.14
+}
+
+function getAverageBitrate (options: {
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const targetBitrate = calculateBitrate({ ...options, bitPerPixel: averageBitPerPixel })
+  if (!targetBitrate) return 192 * 1000
+
+  return targetBitrate
+}
+
+function getMaxBitrate (options: {
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const targetBitrate = calculateBitrate({ ...options, bitPerPixel: maxBitPerPixel })
+  if (!targetBitrate) return 256 * 1000
+
+  return targetBitrate
+}
+
+// ---------------------------------------------------------------------------
+
+export {
+  getAverageBitrate,
+  getMaxBitrate
+}
+
+// ---------------------------------------------------------------------------
+
+function calculateBitrate (options: {
+  bitPerPixel: BitPerPixel
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const { bitPerPixel, resolution, ratio, fps } = options
+
+  const resolutionsOrder = [
+    VideoResolution.H_4K,
+    VideoResolution.H_1440P,
+    VideoResolution.H_1080P,
+    VideoResolution.H_720P,
+    VideoResolution.H_480P,
+    VideoResolution.H_360P,
+    VideoResolution.H_240P,
+    VideoResolution.H_NOVIDEO
+  ]
+
+  for (const toTestResolution of resolutionsOrder) {
+    if (toTestResolution <= resolution) {
+      return resolution * resolution * ratio * fps * bitPerPixel[toTestResolution]
+    }
+  }
+
+  throw new Error('Unknown resolution ' + resolution)
+}