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Topic: Mp3Pro with Lame (Read 3211 times) previous topic - next topic
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Mp3Pro with Lame

Just wanted to share an idea:

*Take a wav file
*encode in mp3pro with whatever you want
*encode your wav with lame, adjusting the encoder delay to match the FhG delay. To do this, you could simply add null samples at the beginning of the wav.
*extract ancillary data from the FhG mp3pro (this is the sbr part)
*mux the sbr part into the Lame ancillary data. To do this you could use plusV tools which already includes such a multiplexer


Here it is, you now have your LamePro file.

Mp3Pro with Lame

Reply #1 –
Well, unless a lowpass is set or the LAME file is encoded at a lower bitrate, wouldn't the SBR portion overlap with the high frequencies in the original LAME encode? Which frequencies does SBR typically encode anyway?
The idea is great though. Where better to use SBR data than with the best encoded mp3s?
 

Mp3Pro with Lame

Reply #2 –
Wanted to try, but with not much luck.
First, the "deinterleave" program, didn't want to separate the mp3pro (still did separate a mv3 correctly).
Next, the lamepv would require a modification so that you could add custom lame switches, because I've found "ABR" modes to be quite bad quality at low bitrates.

So far, this is the best I could get out of LAME at a target of 56kbps (thinking on giving space for the ancillary data. PlusV uses abr 60):

lame -mj -q2 -b56 --athtype 4 --nspsytune --lowpass 10000

Edit: I did this test with lame 3.90.2, which doesn't support --alt-presets cbr  lower than 80. With lame 3.94, It is fully recommended to use that instead, even though I have tested that it gives lower quality than this preset, but this preset sound really bad in 3.94!!! I am going to open a new thread about that.

Note: I am not an expert on LAME, I just followed some knowledge from here, and hearing. You should get these switches as a starting point, not as the best.
The lowpass is set at 10Khz, because the default is 8Khz, (which is good for 22khz wav, but planning to use it for SBR/PlusV, would leave a hole of 3Khz!)

P.s. I did the tests with a wav already resampled to 22Khz with ssrc.


Edit:

@sld : mp3PRO works dividing the spectral frequencies of the file in two blocs, sending the first half to the mp3 encoder, and the second half, to the SBR encoder. This makes so that a 44Khz wave file, would be encoded at 22Khz with mp3, and the SBR decoder would add its part to "complete" up to 44Khz (sampling rate).

What I want to say with this is that there is no overlap area. It's a hard division by half. Probably the best bitrate for mp3Pro might be 80 or 96Kbps and a sampling rate of 48Khz (Quite enough data for the MP3 part, and pumping the SBR part up, to have less artifacts).

And.. another thing.. what do you mean with this?
> Where better to use SBR data than with the best encoded mp3s?

You should be aware that SBR is still more lossy than MP3, so I would not recommend it at all (More after some tests I did myself)