As PysTEL AAC 2.0 supports PNS I tried to encode some songs with -br 64 -production -pns. But the result is quite horrible. This leads me to the conclusion that I am either missing some switches for the PNS mode or the Winamp plugin (FAADPLUG.ZIP) doesn't support PNS yet. What I am doing wrong? :-)

Also I didn't found any more information about the -profile setting. Which one is recommended? Does mode 2 result in better quality? Or is it just some different stream format?

I also tried more codecs at very low bitrates, WMA, MP3Pro, LAME, FHG (in Nero), MPC and OGG RC3. Strange enough LAME sounded much better to me at 80 kbit ABR than FHG (I read all over this forum that LAME cannot handle low bit rates well. I used FHG with VBR lowest setting, CBR and MP3Pro). WMA and MP3Pro did terrible distort the songs (the hihats sounded like some alien coughing, heh), MPC is clearly not optimized for low bitrates at all (I used the -thumb preset). But I was very impressed by OGG RC3 -q1 or -q2. Got clearly the best quality for that bitrate.


bye, Skeeve

PNS is not handled well with current public versions of FAAD. Menno and I have just talked about the issue, and this will be fixed soon.

Anyway, PNS needs "tweaking", for example I use following switch for 64 kbps, 44100 mode:

aacenc -br 64 -c 11500 -pns -psf 7000 -if somefile.wav

Some switches control PNS:

-ptt , PNS switch threshold (for some test samples it needs to be at least 0.6, default is 0.5)

-psf, PNS start frequency, default is 4 kHz - under this frequency PNS might seriously degrade signal

PNS will need more tweaking, of course.

Note - PNS is not a magic wand, or a bandwidth extension (like SBR used in MP3Pro or PlusV) - so the results at 64 kbps can't be spectacular. MPEG commitee is working on incorporation of bandwidth extension tool (probably SBR) so we all are looking forward to see new MPEG-4 profile with SBR.

Please use -profile 0 with PNS... I recommend Profile 0 always

AACEnc also has VBR profiles for low bitrates (-tape and -radio)

I have uploaded latest version of FAAD (Jan 04 CVS Sweep), but I don't know if it supports PNS yet (Had no time to test it).

Regards;

Roberto.

Yes, it supports PNS. It already did, but was not working well. I have now used the PNS code from the new decoder I'm writing, and this works perfectly on the aac conformance streams.

Menno