On Fri, 28 Sep 2012 17:05:42 +0200
Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
> > > Work done from the spec, not tested with any reference encoder.
> >
> > Does a reference mSBC encoder exist somewhere? Or any ideas how to test
> > the new code with something other than bluez just to be sure that it's
> > correct?
>
> I looked at the Bluetooth SIG website and couldn't find a reference
> encoder or sample files. The old SBC reference encoder and decoder don't
> seem to support other block sizes.
>
> SBC Encoder LIB Version 1.5
> Copyright (c) 2002 Philips Consumer Electronics, ASA Labs
>
> Usage:
> sbc_encoder [-jsv] [-lblk_len] [-nsubbands] [-p] [-rrate] [-ooutputfile] inputfile
> [-s] use the stereo mode for stereo signals
> [-v] verbose mode
> [-j] allow the use of joint coding for stereo signals
> [-lblk_len] blk_len specifies the APCM block length, out of [4,8,12,16]
> [-nsubbands] subbands specifies the number of subbands, out of [4,8]
> [-p] a simple psycho acoustic model is used
> [-rrate] specifies the bit rate in bps
> [-ooutputfile] specifies the name of the bitstream output file
> inputfile specifies the audio input file, the major audio formats are supported
>
>
> SBC Decoder LIB Version 1.5
> Copyright (c) 2002 Philips Consumer Electronics, ASA Labs
>
> Usage:
> sbc_decoder [-v] [-ooutputfile] [-pstartpos] inputfile
> [-v] verbose mode
> [-pstartpos] startpos specifies the byte offset to start with decoding
> [-ooutputfile] specifies the name of the audio output file
> inputfile specifies the name of the bitstream input file
>
> And the sample files are all from 2001. We might have to create our own
> ones and our own naive and stupid reference encoder/decoder.
Hi Marcel,
As the first step, some sort of automated testing ("make check") for
verifying sbc encoding/decoding correctness might be useful.
So far I have been using the following quickly hacked script. It just
takes a directory with *.au files, encodes them using different
settings and provides a log with md5 hashes which can be compared with
the reference log:
#!/usr/bin/env ruby
testfiles = []
Dir.new("testsamples").each {|file|
next if not file =~ /\.au$/
testfiles.push("testsamples/" + file)
}
if File.exists?("sbc-test.ok") then
fh = File.open("sbc-test.ok", "r")
okdata = fh.read()
fh.close()
end
outstring = ""
testfiles.sort!
testfiles.each {|file|
["-b32", "-b64", "-b128", "-b255"].each {|br|
["-s4", "-s8"].each {|sb|
["-S", ""].each {|snr|
["-j", ""].each {|j|
["-d", ""].each {|d|
["-B4", "-B8", "-B12", "-B16"].each {|blk|
outstring += sprintf("%s #{file} (#{br} #{sb} #{snr} #{j} #{d} #{blk})\n",
`./sbcenc #{br} #{sb} #{snr} #{j} #{d} #{blk} #{file} 2>/dev/null | md5sum`.strip).gsub(/[ ]+/, " ")
}
}
}
}
}
}
}
if not okdata then
printf("no reference ok data\n")
end
if outstring != okdata then
printf("test failed!\n")
else
printf("test ok\n")
end
fh = File.open("sbc-test.results", "w")
fh.write(outstring)
fh.close()
############################
Though I see this scripts as a dead end, because my media files are a
bit too large for adding to a git repository and these files are
all copyrighted. Some of them have a permissive license (big buck
bunny soundtrack), some of them do not.
Anyway, based on the fact that we use a fixed point encoder for sbc and
its output is deterministic, we can just encode some pseudo random noise
data and compare the checksums/hashes of the encoded results with some
reference values.
--
Best regards,
Siarhei Siamashka
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