From e7d8e2b245491c0a8e008fb570037506d729ff04 Mon Sep 17 00:00:00 2001
From: Chocobozzz <me@florianbigard.com>
Date: Fri, 5 May 2023 10:53:04 +0200
Subject: Fix audio transcoding copy

---
 .../ffmpeg/ffmpeg-default-transcoding-profile.ts   | 61 ++++++++++++++++++++--
 1 file changed, 57 insertions(+), 4 deletions(-)

(limited to 'shared/ffmpeg')

diff --git a/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts b/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts
index f7fc49465..8a3f32011 100644
--- a/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts
+++ b/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts
@@ -1,5 +1,15 @@
-import { getAverageBitrate, getMinLimitBitrate } from '@shared/core-utils'
-import { buildStreamSuffix, ffprobePromise, getAudioStream, getMaxAudioBitrate } from '@shared/ffmpeg'
+import { FfprobeData } from 'fluent-ffmpeg'
+import { getAverageTheoreticalBitrate, getMaxTheoreticalBitrate, getMinTheoreticalBitrate } from '@shared/core-utils'
+import {
+  buildStreamSuffix,
+  ffprobePromise,
+  getAudioStream,
+  getMaxAudioBitrate,
+  getVideoStream,
+  getVideoStreamBitrate,
+  getVideoStreamDimensionsInfo,
+  getVideoStreamFPS
+} from '@shared/ffmpeg'
 import { EncoderOptionsBuilder, EncoderOptionsBuilderParams, VideoResolution } from '@shared/models'
 
 const defaultX264VODOptionsBuilder: EncoderOptionsBuilder = (options: EncoderOptionsBuilderParams) => {
@@ -34,6 +44,10 @@ const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = (options: EncoderOp
 const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum, canCopyAudio }) => {
   const probe = await ffprobePromise(input)
 
+  if (canCopyAudio && await canDoQuickAudioTranscode(input, probe)) {
+    return { copy: true, outputOptions: [ ] }
+  }
+
   const parsedAudio = await getAudioStream(input, probe)
 
   // We try to reduce the ceiling bitrate by making rough matches of bitrates
@@ -95,6 +109,45 @@ export function getDefaultEncodersToTry () {
   }
 }
 
+export async function canDoQuickAudioTranscode (path: string, probe?: FfprobeData): Promise<boolean> {
+  const parsedAudio = await getAudioStream(path, probe)
+
+  if (!parsedAudio.audioStream) return true
+
+  if (parsedAudio.audioStream['codec_name'] !== 'aac') return false
+
+  const audioBitrate = parsedAudio.bitrate
+  if (!audioBitrate) return false
+
+  const maxAudioBitrate = getMaxAudioBitrate('aac', audioBitrate)
+  if (maxAudioBitrate !== -1 && audioBitrate > maxAudioBitrate) return false
+
+  const channelLayout = parsedAudio.audioStream['channel_layout']
+  // Causes playback issues with Chrome
+  if (!channelLayout || channelLayout === 'unknown' || channelLayout === 'quad') return false
+
+  return true
+}
+
+export async function canDoQuickVideoTranscode (path: string, probe?: FfprobeData): Promise<boolean> {
+  const videoStream = await getVideoStream(path, probe)
+  const fps = await getVideoStreamFPS(path, probe)
+  const bitRate = await getVideoStreamBitrate(path, probe)
+  const resolutionData = await getVideoStreamDimensionsInfo(path, probe)
+
+  // If ffprobe did not manage to guess the bitrate
+  if (!bitRate) return false
+
+  // check video params
+  if (!videoStream) return false
+  if (videoStream['codec_name'] !== 'h264') return false
+  if (videoStream['pix_fmt'] !== 'yuv420p') return false
+  if (fps < 2 || fps > 65) return false
+  if (bitRate > getMaxTheoreticalBitrate({ ...resolutionData, fps })) return false
+
+  return true
+}
+
 // ---------------------------------------------------------------------------
 
 function getTargetBitrate (options: {
@@ -105,8 +158,8 @@ function getTargetBitrate (options: {
 }) {
   const { inputBitrate, resolution, ratio, fps } = options
 
-  const capped = capBitrate(inputBitrate, getAverageBitrate({ resolution, fps, ratio }))
-  const limit = getMinLimitBitrate({ resolution, fps, ratio })
+  const capped = capBitrate(inputBitrate, getAverageTheoreticalBitrate({ resolution, fps, ratio }))
+  const limit = getMinTheoreticalBitrate({ resolution, fps, ratio })
 
   return Math.max(limit, capped)
 }
-- 
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