[Mp4-tech] [Audio] SBR Conformance Streams

[Andreas Schneider]

Hello Garima,
the MPEG-4 SBR conformance bitstreams can be obtained from the following 
website: 
http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_IEC%2014496-4_2004_Amd_8_2005_Bitstreams/
Kind regards,
Andreas
mp4-tech-bounces lists.mpegif.org wrote on 06.01.2024 10:40:43:
> Dear Andreas,
> 
> Thanks for your reply.
> 
> Are there any streams available that have only SBR support not PS 
> support for conformance testing ?
> 
> Regards,
> 
> 
> Andreas Schneider <Andreas.Schneider codingtechnologies.com> wrote:
> Hello Garima,
> 
> Garima Singh wrote on 04.01.2024 10:11:58:
> 
> > Hi All,
> > 
> > I have some questions regarding SBR decoding.
> > 
> > In AAC-LC each channel data of one frame is of 1024 samples , but in
> > HE-AAC decoder, 1024 samples output of AAC-LC produces 2048 samples 
> > output from QMF synthesis bank. Could you please explain how are 
> > these mapped to channels? 
> 
> Not sure I understand you. These 2048 samples belong to the same channel 

> as the 1024 samples from the AAC decoder. I.e. they have twice the 
> sampling rate.
> 
> > Also in the SBR decoder, if core AAC decoder works on X sampling 
> > rate then SBR decoder works on 2X sampling rate.My question here is 
> > what will be the sampling rate of input signal (X or 2X) ?
> 
> If the input signal you are refering to is the original wave-file before 

> encoding, then the answer is that this will have the sampling rate 2X.
> The encoder - decoder chain looks like this (this example assumes a 
> sampling rate of 48 kHz of the original file):
> 
> => SBR encoder (fs=48kHz) => SBR bitstream
> PCM-file (fs=48 kHz) < > 
> bitstream
> => 2:1 downsampler => AAC encoder (fs=24 kHz)
> 
> 
> bitstream => AAC decoder (fs=24 kHz) => SBR decoder => output file 
(fs=48 
> kHz)
> 
> The upsampling in the SBR decoder is achieved by using a 32 band 
analysis 
> filterbank and a 64 band synthesis filterbank.
> 
> I hope this helps.
> Kind regards,
> 
> Andreas
> 
> > 
> > Thanks,
> > 
> > 
> 
> > Regards,
> > Garima Singh 
> > 
> > TIVR Communications - Delivering Efficient Solutions for Mobile 
> Multimedia 
> > www.tivr.co.in
> --
> Andreas Schneider
> Senior Research Engineer
> mailto:snd CodingTechnologies.com
> 
> +49 911 92891 -26 (phone)
> +49 911 92891 -99 (fax)
> 
> Coding Technologies GmbH
> Deutschherrnstr. 15-19
> D-90429 Nuernberg, Germany
> http://www.codingtechnologies.com
> 
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> 

> Regards,
> Garima Singh 
> 
> TIVR Communications - Delivering Efficient Solutions for Mobile 
Multimedia 
> www.tivr.co.in_______________________________________________
> NOTE: Please use clear subject lines for your posts. Include [audio,
> [video], [systems], [general] or another apppropriate identifier to 
> indicate the type of question you have.
> 
> Note: Conduct on the mailing list is subject to the Antitrust 
> guidelines found at http://www.mpegif.org/public/documents/vault/mp-
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--
Andreas Schneider
Senior Research Engineer
mailto:snd CodingTechnologies.com
+49 911 92891 -26 (phone)
+49 911 92891 -99 (fax)
Coding Technologies GmbH
Deutschherrnstr. 15-19
D-90429 Nuernberg, Germany
http://www.codingtechnologies.com