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Topic: downsampling lossless before converting to MP3 (Read 4196 times) previous topic - next topic
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downsampling lossless before converting to MP3

hell everyone,
I know that bit depth reduction is pretty much useless to do before converting from lossless to MP3; what about downsampling? for example, if I want a 88.2kHz MP3, and I have a 96kHz source, will LAME downsample, or do everything (including low pass filtering) in the frequency space? Will it introduce artefacts, than could be avoided with another program? (eg sox)

Thanks for the answers!

downsampling lossless before converting to MP3

Reply #1 –
Quote from: karalel on
if I want a 88.2kHz MP3

MP3 does not support that sample rate.  For the sake of discussion, I'll pretend you said one of the supported rates (8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, or 48kHz).

Quote from: karalel on
will LAME downsample, or do everything (including low pass filtering) in the frequency space?

The last time I checked, LAME has a separate sample rate converter and lowpass, although there was interest in combining the two. As far as I know, the encoding portion that operates after the SRC and lowpass takes its input in the time domain, not the frequency domain.

Quote from: karalel on
Will it introduce artefacts, than could be avoided with another program? (eg sox)

I suspect the MP3 compression will introduce more artifacts than the SRC/lowpass used by LAME. However, you could use an external program to perform those steps if you want to compare.

downsampling lossless before converting to MP3

Reply #2 –
Quote from: Octocontrabass on
Quote from: karalel on
if I want a 88.2kHz MP3

MP3 does not support that sample rate.  For the sake of discussion, I'll pretend you said one of the supported rates (8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, or 48kHz).


thank you for your answer

EDIT: removed some useless comment 

downsampling lossless before converting to MP3

Reply #3 –
So what? Max. supported samplerate for MP3 is 48 kHz  (which can contain frequencies up to 24 kHz).

downsampling lossless before converting to MP3

Reply #4 –
Quote from: lvqcl on
So what? Max. supported samplerate for MP3 is 48 kHz  (which can contain frequencies up to 24 kHz).


  I'm tired/hungry, and read that answer too fast...sorry for the confusion