Audio Deterioration?

  • 1
  • Question
  • Updated 1 month ago

Hi! Quick question about audio. Let's say a produce a video as an mp4. Then I use that mp4 in another video. Will the audio degrade, since I technically produced the wav files more than once? I want to say it does, but I haven't tested this extensively. I am using Camtasia 8 right now, if that makes a difference. Thanks!
Photo of alicia.whitney

alicia.whitney

  • 4 Posts
  • 1 Reply Like

Posted 1 month ago

  • 1
Photo of rg

rg

  • 129 Posts
  • 82 Reply Likes
I use Camtasia v8.6, and have experienced some quality loss whenever re-editing prior outputs.  Here is why:
When you produce an MP4, you are transcoding the audio to MP3 format, which is degraded from WAV format.  If you produce an MP4 from that MP4, you will be taking the MP3 and transcoding it again as you produce the new MP4.  I don't think Camtasia (or any other editor) does this without re-encoding the audio.
Here is a workaround that may preserve the quality of the audio as much as possible:
1.  Output the MP4 video and ALSO output a WAV file of the timeline.  (Bear in mind that when you re-output that MP4, the video is now going to lose some quality as well. -- so if you also want to preserve your video quality for the later edit, you might want to try high quality settings for that initial MP4 output.)
2.  When re-editing the video, completely ditch the MP4's audio and use the WAV output as your audio track.

(Edited)
Photo of Ed Covney

Ed Covney

  • 121 Posts
  • 57 Reply Likes
The programs that do the actually compression (fast fourier transforms), will only degrade audio once. Say you convert a wav file to mp3, 128kb. Now you can re-compress  that mp3, 128kb file to another mp3, 128kb file without further degrading the audio. You can then recompress the re-compressed file and sill not affect audio quality. That's why 'digital' is so great. Now if you re-record via speakers and mics (analog devices), then you will get degraded audio.
(Edited)
Photo of rg

rg

  • 129 Posts
  • 82 Reply Likes
If you alter an audio file, you are altering the information inside it.  If you are within Camtasia, even if you stay within an mpeg format, the program is decoding the stream, and then -- upon output -- encoding it all over again.  The process of decoding and re-encoding will result in artifacts (regardless of whether you're editing audio or video).  In audio, the least likely to result in data loss would be an uncompressed format such as WAV.  MP3 continues to live in the podcast world primarily because it is very deeply entrenched -- that is, it is almost universally used & can be played on almost any player -- and because it has been around for such a long time that compatibility issues are rarely encountered.
(Edited)
Photo of Ed Covney

Ed Covney

  • 121 Posts
  • 57 Reply Likes
rg - Apparently you don't understand analog vs digital signals, whether video or audio.  I guess a good question for the TechSmith developers is whether they keep digital content separately layered throughout multiple processes. If they convert digital to analog anywhere and in any process, that would be counter productive. Like playing mp3 files on your home stereo system and recording them through the speakers and mics. Does the text in a callout change? That's a digital layer.
Photo of rg

rg

  • 129 Posts
  • 82 Reply Likes
I checked with a friend who has spent 35+ years as a video editor and consultant in digital media, and who has co-authored texts on video encoding.  I trust his judgment more than mine or yours.
Regarding video text callouts -- they are generated fresh when you insert them.  The video they are keyed over is another story; if you run the video through an editor and re-encode it, you will find that artifacts appear from the process.  This is easy to demonstrate and various editing software programs do this to different degrees.  FCP or Resolve provide cleaner results than many other programs, and a great deal depends on the quality of the source and the encoding of the output.
For audio, it's not as bad as playing digital sound through a speaker and re-recording it with a mic -- that's an absurd extreme example -- but depending on the decoding/re-encoding there is a difference in audio that is measurable and often detectable.  If you stay with WAV, you are using an uncompressed format and it's lossless; if you think 128kbps MP3 re-processed a few times doesn't affect anything, more power to you.
Photo of alicia.whitney

alicia.whitney

  • 4 Posts
  • 1 Reply Like
Thanks for your initial answer rg! I didn't realize my question was going to get such a detailed answer about how compression works (I am a novice myself, but I tried to follow along as best as I could. I also didn't know that there can be differences between analog and digital... that is my lack of knowledge showing...) 

Better yet, there is a workaround! That I do understand, so that was very VERY helpful. I thought I was imagining the deterioration. I will do what was suggested so my videos don't sound as dodgy.

Thanks again!
Photo of Joe Morgan

Joe Morgan

  • 5878 Posts
  • 3065 Reply Likes
Look at it this way Ed,

Digital music is no different than Video. Video is digital as well, and when you compress it again.It loses quality.
That's compression in a nut shell and its as simple as that. If your still skeptical. Perhaps Adobe can convince you.
Here is a mp3 file in Adobe Audition. Its a 128kb file as you can see in Blue Text in the media bin encompassed in red dots.
I'm attempting to export it as a mp3 128kb file. The warning in the window to the right that pop ups says.....

The file 'Attitude Adjustment_OLmp3' is being saved to a compressed (lossy) format You may want to keep a backup of the original file to preserve full audio fidelity. Do you want to continue?



When you export to .wav. You get no such warning or popup ups. It just exports the audio when you hit OK. I didn't see much point in posting a image of that.

Regards,Joe