I am compressing wave files that are currently 44.1 kHz, using:
# lame --resample 44.1 --abr 64 -h foo.wav
These are voice files (hence 64 kbps). I have to force 44.1 using "resample", because with bit rate 64, Lame defaults to 24 kHz.
My question is: Does Lame notice that no change in sample rate is required, and hence not resample, or does it actually resample and thus introduce unnecessary degradation?
Thanks.
there is no need to use 44.1khz for voice files, especially when using 64kbps...
There is no resampling to do, if you are already at the said sample rate. However, maybe you should try lower settings of resample, since the lowpass is probably below 16000 Hz and 32 kHz is probably enough of a sample rate.
there is no need to use 44.1khz for voice files, especially when using 64kbps...
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I understand that. I posted a question on sampling rates last year, and people here helped me. However, I am forced to do it as I am working with someone else who needs it (has a setup that assumes 44.1).
Shade wrote:
> There is no resampling to do, if you are already at the said sample rate.
If I just do
# lame --abr 64 -h foo.wav
then Lame will resample to a different rate, of its own volition. In order to force Lame to keep the original 44.1 kHz you need to use --resample.
Regardless of what should be happening in an ideal world, if anyone can tell me whether Lame will re-calculate the sampling when I nominally "resample" at the original rate, I would be grateful.
What I meant, was : there is no resampling to do, as the -resample 44 switch will simply prevent resampling to another sample rate. (whew! that's a lot of samples!)
I don't see (mathematically) how you could resample a 44kHz signal to another 44kHz signal... unless it's very poorly implemented (eg. multiply, round, divide), it should always give the same thing.
My question is: Does Lame notice that no change in sample rate is required, and hence not resample, or does it actually resample and thus introduce unnecessary degradation?
answering first part: yes
answering second part: no
My question is: Does Lame notice that no change in sample rate is required, and hence not resample, or does it actually resample and thus introduce unnecessary degradation?
answering first part: yes
answering second part: no
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Got it.
Thanks to all for your help.
I think this topic is suitable for my question. Does --resample 44.1 option affect the quality of output file at lower kbps settings? If so, does it improve or degrade that by forcing the original sample rate of the input file (44100Hz) instead of default 24000Hz at 40kbps?
Wouldn't you think that the default sample rate would give you the best overall quality, otherwise why make it the default?
lame --abr 40 resamples to 16000 Hz. And yes, it is better than keeping 44100 Hz.
lame --abr 40 resamples to 16000 Hz. And yes, it is better than keeping 44100 Hz.
I would say, it is
generally better, unless you have a very special sample.
edit: grammar
Wouldn't you think that the default sample rate would give you the best overall quality, otherwise why make it the default?
Good argument. I hear no difference between 40kbps default 24000Hz and 40kbps forced 44100Hz on PC.
I work with 16bit PCM 44100Hz stereo .wav files (classical, latin, folk music, rock, metal) and convert them to mp3 ringtones for a low-class mobil phone. This phone has 2 technical limitations. Ringtone must have mp3 format and file size can't be over 150Kbyte. This means that 30 second long ringtones can have max. 40.00 kbps average bitrate. I try encode input files with mono 40kbps CBR settings:
lame -a -q0 -b40 -mm (-resample 44.1)
Output files with 44100Hz sample rate seem to sound clearer on the phone. Stereo and joint stereo settings have no sense in this case.
Should I encode input files into ABR or VBR to achieve best quality? What about using --lowpass or --highpass filters? I'm unfamiliar with mp3. This format is unfashionable in the age of lossless compressions, low-cost high-capacity storages, and broadband internet connections. It is used only because of mobile devices and webpages.
Don't worry about highpass. It won't gain you anything.
I would definitely try abr.