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#1 2020-07-17 15:52

Improve YT audio in old Iwara uploads

(0. Google and Bing until you find the same video at NicoNico. Download it at 02-06 AM Japan time, in order to obtain the best audio and resolution. Examine the download with SPEK. Doesn't the NicoNico download have better audio than YouTube? And don't forget to check for downloads at PiaPro.)

1. Check the old folder in your PC. Was mp4 and/or Webm downloaded from YouTube? If Mp4 only, too bad. Check the Mp4 with SPEK: If 128 kbit/s AAC, too bad really. (If 192 kbit/s AAC, skip everything here, your audio is already good).

2. Browse to find the video to be downloaded, with Mozilla Firefox.

3. Click a Firefox plugin named: "Youtube Audio and Video Downloader (Dev Edt.)". Click "Download Panel" and peek at the video streams content info. It probably says:
* WEBM audio-only - OPUS 160K
* MP4 audio-only - MP4A 128K
If so, too bad, Iibopus Opus 160 kbit/s is clearly better than the AAC 128 kbit/s you used.

4. Click a Firefox plugin named: "Video DownloadHelper". Download a stream named: ADP - {best size digits} - WEBM.

5. Move the download from the dwhelper folder to the correct folder in your PC.

6. Examine the sound quality of everything with SPEK: http://spek.cc/ . Examine the video resolution and frame rate of everything, for example with VLCplayer/tools/codec info. The old bad sound Mp4 file has the best video resolution? The new best sound Webm file has a watermark? Just extract the best soundtrack and dub it onto the best video.

(7. Open the Webm file with MKVToolNix. Untick "VP9" and all "1 entry", so only "Opus" remains ticked. Chose a destination file with the extension ".opus". Click "Start Multiplexing" to save the Opus soundtrack without any video. NO SKIP THIS STEP.)

(8A. Go to https://www.online-convert.com/ . Select convert to Wav and drag in your Opus file. NO, SKIP THIS STEP.)

8B. Go to https://www.online-convert.com/ . Select convert to AAC 320 kbit/s and drag in your Webm file. (Each old sample will be sampled exactly twice if you convert Opus 160K to AAC 320K)

9. Open the best resolution video file, your old bad audio mp4 file probably, with Avidemux. Click Audio/Select Track and untick the soundtrack. Save the mute file. Close Avidemux.

10. Play and listen to the file, to really confirm that it is mute.

11. Open the mute mp4 video with Avidemux.

12. In Avidemux, click Audio/Select Track, and then click the "Track 0 from video (...etc...)" bar, and finally select ".... Add audio track", in order to add the Wav/AAC/other soundtrack you desire.

(13 A. Still in Avidemux, add the Wav file from step 8A. Click the "Audio Output" bar. Oh, is the Wav option missing, unsupported? Does Wav need to be convertert to AAC in Avidemux before saving? THEN SKIP THIS STEP.)

13 B. Still in Avidemux, add the AAC file from step 8B. Let the "Audio Output" bar remain on "Copy". Save your new best resolution mp4 file, with the 320K AAC soundtrack converted from the best available 160K Opus soundtrack.

14. Go to your old Iwara upload, click the yellow edit button, remove your old bad audio mp4 file and upload your new good audio mp4 file. Your views/likes/comments will not be affected by a mp4 replacement at Iwara.

15. Append your video title with: "2020 ver: 160 kbit/s", to make your viewers aware of the improvement? (Use the current year, if you are reading this after 2020).

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Disclaimer:
There are cases when the uploader actually has uploaded a Mp4 file with 128 kbit/s AAC soundtrack to YouTube. In such cases will the Mp4 and Webm files sound the same, and their spectra will look the same with the same cut-off frequency. To learn how to interpret the cut-off frequencies in a SPEK spectrum, please click this tutorial: https://www.iwara.tv/images/use-spek-better-dls