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Old 25th April 2015, 01:13   #40  |  Link
Motenai Yoda
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Join Date: Jan 2010
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Quote:
Originally Posted by hello_hello View Post
For LAME MP3 the -q option effects encoding speed a fair bit. The range is 0 to 5, with zero being the best. It uses a much slower algorithm than the default -q3, hence the slower encoding but you should in theory get better quality for a specific bitrate. Most encoder GUI's seem to stick to -q2 for LAME by default. Higher quality encoding is very slow. Lame's VBR presets set their own quality too, but maybe you can over-ride that. I suspect QAAC's quality option may work in a similar fashion. Could some encoding speed tests be in order?
indeed lame 3.98+ has a relatively new slighty different -q switch levels than older ones.
Quote:
=======================================================================
algorithm quality selection
=======================================================================
-q n

Bitrate is of course the main influence on quality. The higher the bitrate,
the higher the quality. But for a given bitrate, we have a choice of algorithms
to determine the best scalefactors and Huffman coding (noise shaping).

For CBR, ABR and --vbr-old modes, the following table applies

-q 0 Use the best algorithms (Best Huffman coding search, full outer
loop, and the highest precision of several parameters).
-q 1 to -q 4 Similar to -q 0 without the full outer loop and decreasing
precision of parameters the further fromm q0. -q 3 is the default
-q 5 and -q 6 Same as -q 7, but enables noise shaping and increases subblock
gain
-q 7 to -q 9 Same as -f. Very fast, OK quality. Psychoacoustics are used for
pre-echo and mid/side stereo, but no noise-shaping is done.

For the default VBR mode since LAME 3.98, the following table applies

-q 0 to -q 4 include all features of the other modes and additionally use
the best search when applying Huffman coding.
-q 5 and -q 6 include all features of -q7, calculate and consider actual
quantisation noise, and additionally enable subblock gain.
-q 7 to -q 9 This level uses a psymodel but does not calculate quantisation
noise when encoding: it takes a quick guess.
ie vbr encodes -q0 give bit identical files than -q4, the same for vbr/cbr/abr/vbr-old 5~6 and 7~9
but isn't true for bitrate-based/vbr-old ones 0~4.

ps -q2 for lame was the same as the recommended and now dismissed -h switch
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Last edited by Motenai Yoda; 25th April 2015 at 01:54.
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