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Topic: fair vbr for an mp3 sourced cd (Read 5234 times) previous topic - next topic
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fair vbr for an mp3 sourced cd

Not the kind of thing you people would probably want to see in someones first post.. but

I got a burnt cd from a friend.. and I'm pretty sure it's been mp3 sourced. Spectral view in EAC's process wave thing shows a band at about 15khz, below the line is mainly bright orange/red.. above the line is just dotted with blue. That's the basis for my assumption.

I ususally use alt-preset-standard to encode, but that would be redundant for something like this. I'm looking for a setting for it, I just don't know the names of anything below alt-preset-medium.

So does a 15khz cutoff rougly equate to a particular bitrate, so I can base an encoder setting upon it? I'm not too fussed that it's done badly, and I definitely won't pass it on to anyone else. I just want to put it on my computer without encoding a ton of redundancy into it.

fair vbr for an mp3 sourced cd

Reply #1 –
well redundant it may be -- but re-encoding from original to wav to mp3 to cd-r to wav to mp3 is redundant as well -- face it! The easy and n00b way out of this (although not always 100% easy to tell) is to --alt-preset standard either a few tracks or the whole album, EncSpot scan it , find out what the avg bitrate seems to be for most tracks, and just re-rip the cd in that CBR bitrate. again, no matter what you do the whole scenario is redundant. I hate re-encoding, but sometimes it must be done  good luck

fair vbr for an mp3 sourced cd

Reply #2 –
Quote
I'm looking for a setting for it, I just don't know the names of anything below alt-preset-medium.
[a href="index.php?act=findpost&pid=291737"][{POST_SNAPBACK}][/a]

It's very simple:
--preset extreme = -V0
--preset standard = -V2
--preset medium = -V4

If you want something inferior to medium preset or -V4, use -V5, -V6, -V7....
If the signal doesn't go beyond 15 KHz, it might be interesting to resample the files by using the --resample 32000 command.
Wavpack Hybrid: one encoder for all scenarios
WavPack -c4.5hx6 (44100Hz & 48000Hz) ≈ 390 kbps + correction file
WavPack -c4hx6 (96000Hz) ≈ 768 kbps + correction file
WavPack -h (SACD & DSD) ≈ 2400 kbps at 2.8224 MHz

fair vbr for an mp3 sourced cd

Reply #3 –
Most are ~160 kbps, except for one which is 202kpbs...

so.. vbr with a cap of 160 or 192 and maybe -v5
does that seem sufficient given the circumstances?

fair vbr for an mp3 sourced cd

Reply #4 –
Yeah sure  go for it . . . but trust me , you will feel icky for attempting to do a re-encode . . . it comes back to bite you in the ass . . . one day you will purchase the original and feel catharsis whilst listening to your high-compression musik

fair vbr for an mp3 sourced cd

Reply #5 –
ok, cheers to both of you.

fair vbr for an mp3 sourced cd

Reply #6 –
Quote
... and I'm pretty sure it's been mp3 sourced. Spectral view in EAC's process wave thing shows a band at about 15khz, below the line is mainly bright orange/red.. above the line is just dotted with blue.


Do you mean a more or less constant line around 15 to 16 kHz? This would look more like electromagnetic radiation of a video monitor captured by the recording equipment.

Nowadays many sound engineers seem to be too lazy/stupid to avoid that.

fair vbr for an mp3 sourced cd

Reply #7 –
nah, the line is a distinct cutoff like this:



this is not my file/pic, I found it elsewhere on the forum (thanks to BadReligionPR), but it's very similar.
The only differenec is where its black in this image, I still get some sparse blue bits.

fair vbr for an mp3 sourced cd

Reply #8 –
Where is your cutoff frequency ? Is it 14kHz as in these pictures ?

fair vbr for an mp3 sourced cd

Reply #9 –
Quote
so.. vbr with a cap of 160 or 192 and maybe -v5
does that seem sufficient given the circumstances?


Capping is not a good idea, let the encoder decide how many bits it needs.
Just follow guruboolez's advice - he really knows what he is talking about 

Can you hear anything that sounds like encoder artifacts from your CD?

fair vbr for an mp3 sourced cd

Reply #10 –
Quote
I got a burnt cd from a friend.. and I'm pretty sure it's been mp3 sourced.

Try TauAnalyzer or auCDtect to analyze its source.
Quote
So does a 15khz cutoff rougly equate to a particular bitrate, so I can base an encoder setting upon it?
[a href="index.php?act=findpost&pid=291737"][{POST_SNAPBACK}][/a]

For VBR, -V 7 has a lowpass transition band at 14581 Hz - 14968 Hz
For ABR, average bitrates from 88 to 103 have a lowpass transition band at 15115 Hz - 15648 Hz
For CBR, 96kbps has a lowpass transition band at 15115 Hz - 15648 Hz

fair vbr for an mp3 sourced cd

Reply #11 –
Integrating:

auCDtect gives them a 95% chance of being mpegs.

Sunhillow: Wouldn't a non-capped encode be equivalent to transcoding from a lower to higher bitrate? Or is there some possibility of audio that can be "salvaged" by not having a cap?

If not, in the case that it's 96kbps CBR (lowpass at ~15khz), wouldn't 192 still be a generous cap at V5?

fair vbr for an mp3 sourced cd

Reply #12 –
You can also try encoding it in MPC since it's bitrate is somewhat dependant on lowpass filtering and stuff… If -q5 gives you a good result, then just rename it to *.mp3.mpc and that's all.
Infrasonic Quartet + Sennheiser HD650 + Microlab Solo 2 mk3. 

fair vbr for an mp3 sourced cd

Reply #13 –
Quote
Integrating:
auCDtect gives them a 95% chance of being mpegs.
[{POST_SNAPBACK}][/a]

I wouldn't rely too much on auCDtect...

Quote
I've just encountered something pretty strange. I used the command line tool and the result using -m0 was 90% probability that it's source was lossless. Anyway, I encoded that file using LAME 3.96.1 -V2 and decoded it back to wav. Now, all of a sudden that file got a probability of 95%!
[a href="index.php?act=findpost&pid=286779"][{POST_SNAPBACK}][/a]



and check this out: [a href="http://www.hydrogenaudio.org/forums/index.php?showtopic=32828&view=findpost&p=286836]http://www.hydrogenaudio.org/forums/index....ndpost&p=286836[/url]
--alt-presets are there for a reason! These other switches DO NOT work better than it, trust me on this.
LAME + Joint Stereo doesn't destroy 'Stereo'

fair vbr for an mp3 sourced cd

Reply #14 –
I've got an interesting information.

I had an mp3 (3.90.3 APS ripped) allowing freq. up to 19.5 KHz
It was 207kbps

Then I applied LPF of 16KHz and burnt a AudioCD using that MP3. (Just like the case of original poster)

Then I ripped it again using 3.90.3 APS only. And what I got was VBR mp3 (of cource), with 16KHz cut-off (but obviously). And bitrates were 135kbps.

So I think APS algorithm decided to encode this signal at lower kbps.

Hence, There is no problem using APS. It correctly identifies the need and encodes like-wise.

FYKI:
Song: "Rock The Party" by Bombay Rockers

and

Quote
TRANSCODING IS ALWAYS BAD! BUT JUST IN CASE... IF YOU MUST USE IT...


Regards,

M

fair vbr for an mp3 sourced cd

Reply #15 –
I'm no expert by any means, but wouldn't alt-preset standard give you the best quality in every scenario? Doesn't re-encoding lower the bitrate each successive time, therefore there's no need in setting some lowpass since APS gives you the best sound possible?

fair vbr for an mp3 sourced cd

Reply #16 –
Re-encoding can actually raise the bitrate due to added quantization noise during the first encode.
"You can fight without ever winning, but never win without a fight."  Neil Peart  'Resist'

fair vbr for an mp3 sourced cd

Reply #17 –
Quote
I'm no expert by any means, but wouldn't alt-preset standard give you the best quality in every scenario? Doesn't re-encoding lower the bitrate each successive time, therefore there's no need in setting some lowpass since APS gives you the best sound possible?
[a href="index.php?act=findpost&pid=310509"][{POST_SNAPBACK}][/a]


As I explained, I was experimenting! I do not need to set low-pass. I was EXPERIMENTING! I've even concluded that APS selects the best range.
 

fair vbr for an mp3 sourced cd

Reply #18 –
Quote
Re-encoding can actually raise the bitrate due to added quantization noise during the first encode.
[a href="index.php?act=findpost&pid=310514"][{POST_SNAPBACK}][/a]


I Think you'd like to check this out. 
If you would  please download Dirom's Modified Compile (just because it's easy drag and drop. it works same as original one). and drop any APS encoded mp3. let us say test.mp3. the output file will be smaller and with smaller kbps. Do that again and that would be smaller again

original wav - 4.9MB (29 seconds)
test.mp3 206kbps 736KB
test.mp3.mp3 201kbps 722KB
test.mp3.mp3.mp3 199kbps 710KB
test.mp3.mp3.mp3.mp3test.mp3.mp3.mp3.mp3.mp3 193kbps 698KB