[Mp4-tech] [Audio] Erroneous bit streams...

[Umang Garg]

Hello Guha, 
In broadcast environment you may encounter packet loss and stream corruption
as two primary errors. 
For HEAAC:
Stream corruption may be checked via CRC. ADTS format has a CRC check along
with a separate CRC check for SBR decoding.
Similarly, packet loss may also have to be handled gracefully within the
decoder. In case of a loss of frame(s) the simplest technique is insertion
of a silence frame (to maintain synchronization) but a more appropriate
technique would be gradual muting.  As far as I know, the HEAAC standard
does not say much about packet loss in general or the muting technique in
particular. You may have to make your own decisions on that.
Regards,
Umang  
  _____  
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of guhapriya ganapathy
Sent: Thursday, May 18, 2024 5:19 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] [Audio] Erroneous bit streams...
Dear all,
Suppose you have an audio codec which is a part of a broadcast system (any
system for that matter). What are the possible errors that might creep in
the bitstream when it reaches the decoder? (There will be CRC check for each
packet in the network layer, but I am concerned about the bitstream when it
reaches the decoder.. what are the chances that the bit stream is
corrupted?) 
Taking AAC HE as an example, Coding Technologies provides erroneous
bitstreams for SBR (although SBR has CRC check) as a part of its
certification package (wherein for example one bit in every third frame is
corrupted - a random corruption!), whereas ISO does not(?) provide erroneous
bitstreams. Of what value are erroneous bitstreams to the decoder? Is there
a value add in generating erroneous bitstreams for decoders? If so, what is
the approach so that it matches what happens in the real time?
Regards,
Guha Priya.
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