Uploading blocked audio recordings to VKontakte

I am a reader of Habr for a long time, but I have not written a single article yet. This post prompted me to write this article: Vkontakte Audio Blocking. Restoring the playlist .

I liked the methods used by the author to bypass the VKontakte filter, but as a person who has been involved in sound processing and writing music for a long time, I can say that this is not the best solution that can be taken in this situation, and here's why:
1. The quality goes bad audio recordings, with repeated conversion and intentional deterioration.
2. Cutting a piece of the work changes the music.

I suggest a slightly different approach to solving this problem. Who is interested in the topic - I ask for a cat. I’ll talk in more detail about several methods that can bypass the filter, including a method that allows you to download locked music without changing its content (i.e., completely preserving the sound).

All tests were performed in the Audacity program. For analysis, a song was chosen, performed by rapper Pitbull and singer Marc Anthony, the name is Rain Over Me. This song is suitable for the test for several reasons: it is “banned” by VKontakte, its spectrum contains all frequencies to the full extent, it has both “quiet” and “loud” parts, which will allow you to experiment with dynamics. To begin with, make sure that listening to an audio recording is impossible, because It was deleted at the request of the copyright holder:
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As you can see, it’s true that the original audio recording was removed, and when we try to download the same one, we will receive a warning about copyright infringement:
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Downloading the same audio recording, but under a different name, was also unsuccessful. Tags in both entries (original and version with a changed name) were absent.

Now let's try to download the same audio recording, slightly changing it in some way.

Filter Bypass Methods


1. Change the tonal balance of the entire work, or part of it, that is, processing by the equalizer:

In my opinion, this is the easiest method. Consider several cases of using EQ:

Here I immediately give the result of what I came to, in fact, I unreasonably started trying to “feed” VKontakte an audio recording with a slightly changed tonal balance, so that it was almost impossible to hear the difference (for example, I used the low-pass filter and HPF with very soft settings - the difference in sound was negligible). VKontakte rejected entries with such changes, but, interestingly, accepted it, processed like this:
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This means that recognition occurs only in the mid-frequency range, high and low are not affected. The first option is the equalization of the entire track: you need to cut out a small area of ​​the mid-frequency range. I tried to apply EQ only on a small section of the track - it failed to load.

2. Adding noise

In comments to the article, the user Gorthauer87 suggested “a little mix up some noise imperceptible to the ear”. The correct thought, in fact, it was the very first to me that occurred to me. In the recording industry, dithering has long been used , which is nothing more than adding noise, though now noise is going through the stage of noise shaping - i.e. the frequencies most audible to the human ear are removed from it.

Adding enough white noise in order to clearly hear it did not help to download the audio recording. This method is not suitable for us, because if the noise can be heard, then we can assume that the audio recording is corrupted and cannot be listened = (

3. Work with track dynamics

After processing the entire track with a compressor with fairly “soft” settings, the audio recording was successfully downloaded. I give a screenshot of the compressor settings: It is
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quite problematic to hear the difference with the original to an unprepared listener, and if you listen with headphones or with not very high-quality acoustics, it is impossible.

Crown way

But this method surprised me with its simplicity, while it turned out to be the highest quality of all considered earlier. You just need to add a small piece of an arbitrary signal to the end of the track (after the music has finished). As a result, the useful signal does not change in any way, but the VKontakte website does not try to block such tracks. Specifically, in this example, I added a sine wave of 440 hertz to the end of the work, the duration of the noise is about 1 minute.

If this article will be of interest to readers, then I can take a closer look at each of the ways to download music (I guess that the “crown” method will be “covered” soon), depending on the material (classical, rock, pop, electronics). Each of the options will work better on one material and worse on another, that is, somewhere more noticeable to a person, and somewhere practically without changing the source.

The article was not as complete as we would like, for the reason that my DAW refused to work and began to throw an error (so I spent all the work in Audacity). I suppose that there are several more ways that will work:

1. Working with a stereo base (expanding / narrowing it)
2. Processing the entire track with a multi-band exciter
3. Multiband compression of the mid-frequency range, to a much lesser extent than discussed in the article.
4. Adding a very weak reverb signal indistinguishable by the human ear.
5. Expansion , both single and multiband.
If there is an opportunity to work on a powerful DAW, then I can consider these cases.

Conclusion


I am not a supporter of copyright infringement, since I am involved in the creation of music, but I believe that the situation with copyright has now passed all the permissible limits. Bans and restrictions are only temporary solutions that will not eliminate piracy, it is necessary to solve the problem completely, stimulating alternative means music distribution. In fact, who among those people who suffered from the deletion of VKontakte audio recordings will go to the store and buy a CD? Or buy music over the Internet?

* The sample audio was taken from youtube.com, where it is freely available by the copyright holder. Audio was used exclusively for research purposes.

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