First of all thank for all the replies.
Date: Fri, 08 Dec 2000 09:48:25 +0100
From: Per Bolmstedt <[EMAIL PROTECTED]> Subject: Re: [MP3 ENCODER] MP3
reencoding of other compressed formats
(...)
>Is there really a fundamental difference between this and other audio
>sources? Much audio you would hear is probably encoded in some way
>already. I know several radio stations that play MP2 and MP3 files,
>and when you record that music and encode it with LAME, that's the same
>sort of re-encoding I do when I convert Real Audio RM files to MP3.
this is a very interesting remark although in my experience I found out
it's very easy to tell if you're reencoding an mp3 file, since VBR will
produce a file that is 99% CBR at the original bitrate the file was
encoded (assuming that the original file wasn't VBR to begin with). Of
course if the compression format was different it's impossible to infere
anything.
>It would be interesting if you could compare your captured Real Audio
>stream against your ~1.5 times larger LAME MP3 stream in terms of added
>artefacts, added noise etc.
I've downloaded the RealEncoder program and I've been
encoding the same WAV (a Pink Floyd song ripped with EAC) with different
codecs (and bitrates), decode them and reencode with LAME. The encoder
is RealProducer Basic 8.5, to decode I played the songs with RealPlayer
8 and saved the stream to WAV using Total Recorder 3.0b.
First results:
- RealAudio sucks. Even their 96kbps (the high end for streaming media
-especially live radio) cuts off everything above ~15.5KHz while
attenuating noticeably all frequencies above ~12KHz. The 64Kbps codec is
not much worse. Moreover the dynamic range is reduced at all frequencies.
- LAME 3.87MMX with settings -v -V 1 -m j -h -q 1 -b 64 works well for
the file encoded with the 64Kbps codec. the result is indistinguishable
from the RA file. The only difference is that the steep cutoff at 16KHz
is smoother (therefore there may be some artifacts introduced there).
This effect is more noticeable when encoding RA96 with -b 64.
- using -b 96 seems to preserve the original file completely although
the smoother transition at ~16KHz is still present.
- file sizes: original WAV 1:27, 14.27MB. RA 64: 708KB, RA 96: 1.03MB.
RA 64->mp3 -b 64 1.43MB, RA 64->mp3 -b 96: 1.51MB. RA 96->mp3 -b 64:
1.44MB, RA 96->mp3 -b 96: 1.52MB.
I'd say that -v -V 1 -m j -h -q 1 -b 96 is a safe way to reencode
preserving as much of the -little- quality of the RA stream, although I
haven't tried using ABR yet.
A final comment on the programs that were suggested.
Streambox Ripper I think is bogus, I don't think it does anything but
decoding and reencoding on the fly (with the nice addition of allowing
to reequalize the output).
ASFrecorder is a wonderful piece of software. It allows recording of all
ASF media files which is great for videos.
Voquette allows recording of the direct stream but is difficult to
schedule and the resulting file is impossible to modify. Great for not
live streams to be saved in their entirety.
X-Fileget and Streambox VCR (same thing): the only versions around are
old betas before a lawsuit from Real blocked the development. They seem
to work well, but not under Win2000 where all connections time out. I
can't try it since I'm only running 2000/redhat 6.1 .
Thanks again for the feedback and for making LAME a success!
Ciao,
GD
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