I'm working with many stripes of uncompressed WAV sounds. Now I want to make them be just one MP3 stripe.

My problem is: There is other files to render in the same situation. So in the end, there will be files rendered as MP3 in need to be rendered again as MP3 to obtain the final cut.

I would like to know what Blender does in this situation: Does the quality goes down even more?

  • $\begingroup$ Detailed version of this question in Blenderartists: link $\endgroup$
    – chicOrtiz
    Commented Jun 17, 2016 at 23:26
  • 3
    $\begingroup$ Every time you compress a file you loose quality. If you take a compressed file and re-compress it again you loose even more... $\endgroup$
    – user1853
    Commented Jun 17, 2016 at 23:28
  • 1
    $\begingroup$ if only blender allowed passing custom arguments to ffmpeg... $\endgroup$
    – user2816
    Commented Jun 17, 2016 at 23:40
  • 1
    $\begingroup$ In order to make this question useful to other users, we do not put (SOLVED) in the title. On Stack Exchange networks, accepting an answer is enough to show that the answer solved your problem. $\endgroup$ Commented Jun 18, 2016 at 21:41

1 Answer 1


It boils down to if you are increasing the compression or not, and has nothing to do with Blender.

The reason for this is that any given level of compression will "shape" the encoded values into the compressed shape required. Subsequent compression at the same degree using the same compression technique seeks the exact same shape. Given that the algorithm is seeking the shape the data is already in, very little further degradation will occur typically.

You can test this by trying to encode a JPEG image twice at the same compression level. What you should observe is very little encoded data value shift, and even possibly a growth in file size.

As a general rule, this is a poor option for a pipeline, and it would be much more prudent to keep your interchange data in a lossless and uncompressed format, and encode once and only once. Even expanding an MP3 to a WAV can help you here in theory.

  • $\begingroup$ Hi Troy! Thanks a lot for your answer. I needed to hear that from someone else :) (Now I understand that I was searching excuses to be lazy). It passed trough my mind do the same comparison that you did with pictures. But since I'm really starting with sound, I was beliving that it would be wrong. Thank you so much for the clarification! $\endgroup$
    – chicOrtiz
    Commented Jun 18, 2016 at 21:35
  • $\begingroup$ Bear in mind the answer is just a loose approximation, and there are many variables at work. $\endgroup$
    – troy_s
    Commented Jun 18, 2016 at 21:57

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