Date: Thu, 6 Aug 2009 03:05:07 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: "b. f." <bf1783@googlemail.com> Cc: freebsd-multimedia@FreeBSD.org Subject: Re: mp3 VBR histogram? Message-ID: <20090805235234.H19821@sola.nimnet.asn.au> In-Reply-To: <d873d5be0908050251u1562609dh595b54e1e47f0137@mail.gmail.com> References: <d873d5be0908050251u1562609dh595b54e1e47f0137@mail.gmail.com>
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On Wed, 5 Aug 2009, b. f. wrote:
> >does anyone know anything that can produce the sort of ASCII histogram
> >that lame produces while encoding in VBR, from an existing .mp3 file?
> >
> >I'm interested in analysing the bitrate distribution of frames of a VBR
> >live stream, though I don't mind saving it to a disk file if necessary.
>
> Any application that can sweep through an mp3 and read the frame
> headers should have code that you can adapt for this purpose, and
> there are many such pieces of software in Ports (every mp3 decoder,
> and many utilities). If you want something ready-made, and efficiency
> isn't of paramount importance, you could use, for example,
> audio/mp3plot or audio/mp3stat on files.
>
> I've dumped frame bitrates of mp3 files before from the command-line
> using audio/mp3_check and something like:
>
> mp3_check -avv sample.mp3 | awk '/BitRate/ { print $2 }' -
192
160
160
320
96
160
112
160
128
160
128
160
160
224
That works well for extracting the raw frame bitrates, might try
scripting up a simple histogram from that, the next rainy day.
> audio/py-mad, a python interface to audio/libmad, has some example
> code for reading mp3 streams, and could also be used for this purpose.
Thanks for the good clues. Speed's not an issue; more about occasional
sampling than realtime monitoring. mp3plot looks good on spec, still
building; compiling boost very nearly ran this old laptop out of swap!
cheers, Ian
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