Audio restoration: How do you repair the old noisy audio of VHS footage?

[Mitra]

There are many articles and filters about video restoration in the forum,
but I couldn't find a method or filter for audio restoration.

[Emulgator]

A source sample would be helpful.

[johnmeyer]

"Audio restoration" is a phrase with absolutely no meaning. You need to provide a sample clip, as Emulgator already suggested, and you also need to describe what you think is wrong with the clip. Sometimes other people don't see or, in this case, hear what it is you find objectionable.

Some audio restoration can have wonderful results. You can reduce hiss (a.k.a. single-ended noise reduction); remove unwanted noises; eliminate pops and ticks; adjust bad levels; and even, in some cases, reduce distortion, such as what happens if the audio gain was set too high during recording, resulting in clipping.

However, it is difficult to impossible (AFAIK) to increase the fidelity of a VHS linear track, especially if recorded in the 6-hour mode. This is often what people dealing with old VHS tapes want to do because the early units only recorded linear audio, and the bandwidth was often less than AM radio.

I keep hoping that AI algorithms can be applied to this last problem, and the missing upper frequencies can be guessed at using some sort of training model. Perhaps that already exists, but I haven't encountered it yet. I'd pay good money for something that works. By "good money" I mean the kind of money I had to spend to buy iZotope RX.

[Frank62]

I keep hoping that AI algorithms can be applied to this last problem, and the missing upper frequencies can be guessed at using some sort of training model. Perhaps that already exists, but I haven't encountered it yet. I'd pay good money for something that works. By "good money" I mean the kind of money I had to spend to buy iZotope RX.

RX 10 and 11 have an A.I. feature called "Spectral Recovery" which tries exactly this. It is sometimes astonishing, but always (in my tests) also producing artefacts and hissing in high frequencies. I tried it so far only with very bad sources, so maybe there is something usable - or will be in near future.

[AVIL]

IMHO avisynth is not the best tool to enhance audio. I usually demux audio and process it with Audacity, my preferred tool to process audio. About the subject of "Sprectral Recovery" there are an interesting thread in hydrogenaud.io https://hydrogenaud.io/index.php/topic,126345.0.html

[johnmeyer]

RX 10 and 11 have an A.I. feature called "Spectral Recovery" which tries exactly this. It is sometimes astonishing, but always (in my tests) also producing artefacts and hissing in high frequencies. I tried it so far only with very bad sources, so maybe there is something usable - or will be in near future.Thanks for telling me that. I haven't upgraded RX for many years. It is probably time to pull out the wallet ...

[edit]Also, thanks for the link to fat_llama. I tried to find a before/after demo, but haven't found it yet. I'd like to hear the results.

Also, AVIL's recommendation of Audacity is a good one. AVISynth doesn't do much for audio, and Audacity has quite a few pretty good tools and is either free, or really cheap.

[Mitra]

Thank you all!,

Unfortunately, I'm not allowed to share the audio source , but I downloaded an old, distorted, and corrupted sample that is similar to mine from this website (https://freesound.org/people/AlienXXX/sounds/253409/).

Please tell me how to repair this file (https://media4dco.com/downloads/253409__alienxxx__radio_cairo_voice_noises_02.zip) (677 KB)

(it is an extremely distorted speech recorded from an AM radio)

[Frank62]

If someone is able to repair THIS, would be some holy grale.
I also have a German dub of an U. S. Western series since years, which someone recorded on a tape in 1969 with a microphone standing on the tv... Sounds similar. The last relict of the German dub that was destroyed later.

[Mitra]

If someone is able to repair THIS, would be some holy grale.
I also have a German dub of an U. S. Western series since years, which someone recorded on a tape in 1969 with a microphone standing on the tv... Sounds similar. The last relict of the German dub that was destroyed later.


Do you think that even using AI cannot be effective?

[Frank62]

I really have no idea. But I just tried to get something out of your source with the mentioned RX-AI-Spectral-Recovery... Result: Some more high frequencies that extend the bad things. Tried then several equalizing before A. I., a. s. o., without any success.
But when I look at the A. I. possibilities you have with video since a few years, I would say: This will work (or does already?) in quite near future...
But I am really no expert in A. I. and Audio.

[johnmeyer]

I didn't even attempt to repair it with Izotope RX. I have various guesses about how it could have gotten so distorted, but it sure sounds like an old tube amp with a failing tube, or a bad capacitor that reduced the voltage across the tube. Either way, it sounds like distortion from a very non-linear amplifier, and I'm not sure whether that can be fixed, even with AI training.

[Mitra]

I tried the last trial version of Izotope RX, but without success.

[johnmeyer]

I tried to tell you that RX would be a waste of time. You cannot improve this audio.

[Mitra]

I tried to tell you that RX would be a waste of time. You cannot improve this audio.

I understood your intention, but I just wanted to try it myself and confirm your statement. :)

Thank you very much.

[Mitra]

Do you think the claims made by the following website are possible?

https://tmtv.net/video/video_restoration/

[Frank62]

Which claim do you mean?
The one with "baking" the tape I can confirm: This worked several times for us in the past. The tape can be played ONCE - then it is destroyed. But better than nothing...
I can read nothing about your sound problem there?