___Best quality on YouTube for your audio uploads____

 

1. If you already have a ready video which is not just a one frame (e.g. a cover all over the video), download MKVToolnix and replace audio track with lossless one instead of rendered lossy track. You will avoid recompression or reencoding, unlike it is during rendering normal video.
2. If you can, upscale the video to at least 1440p or greater. It will avoid deferred transitioning of your AAC (16kHz) audio stream to Opus (20kHz) when your video gets popular, or it's old enough (for current YT audio format, check statistics for nerds). QHD/+ makes your video play in better Opus codec from the beginning, and it will sound better than after deferred transition from AAC to Opus on FHD clip (Opus audio streams checksums differs in FHD and QHD videos despite the same video source file and most likely something is broken on YT side during the process, though both Opus files are 20kHz, so the file in FHD is not recompressed from AAC, perhaps from other audio file created during YT rendering, but not from the source video).
3. Alternative - if you have just one image to make a video of it (e.g. cover), make sure it’s at least 1440p or greater. If not, simply upscale it (e.g. XnView has some basic upscaling filters). Then place the image nearby this batch FFmpeg script with your lossless audio files. It will render videos with the same audio streams like original files, but muxed into your output MKV files (you can check in Foobar2000 for Audio MD5 comparison or by using AudioMD5Checker, if MD5 checksum is not embedded when looking in F2K file properties) so it won’t be recompressed on your end while making a video for upload on YT (yes, YT supports MKV!). It’s faster than MKVToolnix and you can convert multiple files with the same image at the same time (it's very fast, incomparable to normal video rendering, and output is only 1 FPS, so it will buffer in YT also very fast).
4. You don’t have to wait till YT stops processing your HD version for Opus to appear. It happens at a point when FHD resolution appears before QHD when processing is still in progress. So check it out from time to time before you hit the publish button.
5. Because Opus is 16 bit, and your input audio file in Matroska container might have higher bit depth, it’s good to compress your input file to Opus VBR 128kbps for testing purposes to check how it will sound on YT (of course don’t use it later for MKV file). Downsampling performed by the encoder can occasionally introduce some unwanted changes to the sound. It’s the most noticeable when audio input is 64 bit, but smaller can be still good enough.
6. YouTube videos from early 2010 on archive.org have 192kbps AAC for 1080p (example) (thx theamogusguy)
7. If you deal with some harshness on your YT audio uploads with original 44kHz sample rate audio in the uploaded video file, consider upsampling them manually to 48kHz before upload. It will bypass the built-in Opus resampler. You can do that using e.g. Izotope RX (smooth). Although it can sound smoother just because of forced upsampling on file import to 32-bit in RX Editor and downsampling during export, esp. without dithering.
   Alternatively, you can use dBpoweramp/SSRC (F2K plugin) or SoX in the newest Foobar2000 x64 and save the output as lossless format.
   Currently the best resampler on the Hydrogenaudio SRC chart is:
   https://github.com/rorgoroth/mingw-cmake-env/releases/tag/latest
   Usage:

ffmpeg -i "C:\input96or48.wav" -af asf2sf=dblp,ardftsrc=44100:quality=61656210:bandwidth=0.9941249 -c:a pcm_f32le C:\output44.wav

If you don’t deal with clipping, delete -c:a pcm_f32le to use just 16-bit output (other formats).

24GB RAM recommended. It doesn’t track progress. It can take more than 10 minutes in an insufficient RAM scenario (and normally less than 5 for 5-minute audio).

PS. E.g. 96>44kHz resampling on 4:20 file requires 40.5GB of memory. With 16GB of physical memory, it will require 25GB of SWAP (by default, it will be used from C:\), and if you run out of disk space, it will briefly show "Cannot allocate memory" during executing the command. Make sure that you didn’t limit the SWAP manually. Consider turning on SWAP on two SSDs to accelerate the process.

1. Since now MVSEP supports batch API conversions, you can use Case Changing in Ant Renamer to reestablish uppercase letters to song titles for your YouTube uploads.

So if you want to batch upload on YouTube the name will not appear as "song artist song title" but "Song Artist Song Title" (since YT removes dashes and commas etc.)

1. It seems like 720p is now enough to get Opus after upload (thx dca100fb8; points 9 and 8)
2. Safari browser probably still don’t support Opus, so it rather always uses AAC 128 kbit/s 44kHz audio stream on YT for all videos instead (should be available to check in PPM on played video>Stats for nerds)

 

Note: Google can block your account if you use AdBlocks on YouTube. Use some spare one you won't regret losing for it.