[Mp4-tech] [Audio] SBR bitstreams which require down sampling

[Andreas Schneider]

Dattaguru,
Meanwhile there are new conformance bitstreams (well, actually the 
bitstreams are the same, they only have new names), where you can conclude 
whether downsampled SBR is signaled or not from the filename even easier. 
Basically your understanding is correct, except that there is one more 
bitstream, which signals downsampled SBR (new name: 
al_sbr_sig_24_2_fsaac24_sig1.mp4).
You should only be aware of the fact that such a decoder is not MPEG-4 
conformant, since the standard requires that downsampled SBR has to be 
used if this is explicitely signaled.
Best regards,
Andreas
mp4-tech-bounces lists.mpegif.org wrote on 2023-12-16 06:56:57:
> Hi Experts,
> 
> I want to know which among the SBR bit streams require
> down-sampling? 
> I have sbr_sr_*.mp4 bit streams which are provided for
> testing different sample rates.  In case, I dont want
> to support down-sampling, then which of the bit
> streams are to be omitted (i.e., not to be
> considered)?
> To my understanding, Bit streams which require down
> sampling are
> sbr_sig_3.mp4 
> sbr_sr_03_03.mp4, sbr_sr_04_04.mp4, sbr_sr_05_05.mp4,
> sbr_sr_06_06.mp4, sbr_sr_07_07.mp4 and
> sbr_sr_08_08.mp4
> Hence these bit streams are not to be tested if my
> decoder doesnot support down sampling?
> 
> Thanks in advance for your valuable support and the
> answers.
> Thanks and regards,
> Dattaguru
> 
> 
> 
> 
> 
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Andreas Schneider, Research Engineer
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