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Topic: Deviation from MPEG-4 14496-3 bitstream syntax (Read 3134 times) previous topic - next topic
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Deviation from MPEG-4 14496-3 bitstream syntax

Hai,

        Recently I saw a deviation from  MPEG-4 14496-3 bitstream
syntax in reference codes like ISO and FAAD2.
According to the specification in individual_channel_stream() function,
if tns_data_present, then tns_data() is called irrespective of the
object type.  But in the reference codes, for Error Resilient
stream(object_type >= 17) this is not the case. They first check 
tns_data_present bit and then without reading tns_data() (if
tns_data_present is 1) they check the next flag bit, which is
gain_control_data_present. Then they check for
aacSpectralDataResilienceFlag, do reordered_spectral_data() and only
after then read tns_data.

When I encoded my bitstream according to the spec, its not getting
decoded. But now when I changed it in the order in which bits are read
as I mentioned above, its correctly decoding.

Why is it so?? Such bitstream syntax is not mentioned in specification.
Please clarify my doubt.

Regards
Pratheek