Audio clipping in MP4 and MP3

[Giampy]

Hi all.

I downloaded a video by YTD, I got a MP4 file, and then I opened it by Audacity. The sound was almost all clipped. Almost all the spectrum was cutted/flattened at its edges.

Then, using YTD again, I converted the file in MP3 lowering the volume. Then I was going to open the MP3 by Audacity again.
It was only an extreme try, a curiosity, no hope to see a different result. In fact it's impossible that a clipped sound can magically turn into a regular sound, right?

Well, when I opened the MP3 by Audacity, I realized that the sound was no longer clipped. It was fine, it was whole.

How may it be explained?

[TaoPhoenix]

Guessing - maybe in the export settings of YTD, there is on the audio "allow clipping". Because that is there on the audacity side when you are exceeding some sound thresholds.

[Curt]

or maybe the converter in your Audacity's default setting is "Normalize Gain":

[Joe Hone]

Almost all the spectrum was cutted/flattened at its edges.

-Giampy (May 30, 2015, 01:48 AM)

The cutted/flattened edges you mention are the visual waveforms that have been hardwall/brickwall limited. The "normalize" function Curt mentions is a preset limiter. When music is produced at that fine line just below clipping, any number of variables with your system might boost the signal just enough to exceed that line and cause audible clipping. As for your fix re the clipping, I produce for radio and have to leave about -5db headroom on the radio shows or else some stations run into problems with their download/playback/upload or broadcast systems boosting the signal and causing clipping. The -5db leaves plenty of room to compensate for that. You did the same by lowering the audio on the YTD audio - got it far enough away from clipping that Audacity could then manipulate the sound to your satisfaction. I think you'll only have clipping where the audio is been mastered at those extreme levels.

[Giampy]

Curt, where is that window? I can't find it.

[tomos]

The cutted/flattened edges you mention are the visual waveforms that have been hardwall/brickwall limited. The "normalize" function Curt mentions is a preset limiter. When music is produced at that fine line just below clipping, any number of variables with your system might boost the signal just enough to exceed that line and cause audible clipping. As for your fix re the clipping, I produce for radio and have to leave about -5db headroom on the radio shows or else some stations run into problems with their download/playback/upload or broadcast systems boosting the signal and causing clipping. The -5db leaves plenty of room to compensate for that. You did the same by lowering the audio on the YTD audio - got it far enough away from clipping that Audacity could then manipulate the sound to your satisfaction. I think you'll only have clipping where the audio is been mastered at those extreme levels.

-Joe Hone (May 31, 2015, 09:55 PM)

that was interesting