Unfortunately one way to define variable bit rate is its compressed CBR.
Rather than defining at the protocol level "insert comfort noise here" at the compression level you get bitstream level "I donno what this stream is at a higher level, but replace the next 1000 bits with zeros".
That's if you do simple sampling. I donno about weird higher level vocoders. I think you could create a constant bit rate vocoder that really is constant. But it'll likely be uncompressible if its a good one because a vocoder basically is a compressor that's specifically very smart about human speech input. If your vocoder output is compressible its not a good one.
I think if you replaced your compression step with run it thru a constant rate vocoder you'd get what you're looking for. Probably.
No, he's saying you compress CBR, then encrypt. Not compress CBR -> gzip -> encrypt or something silly like that.
CBR audio codec, then encrypt gives you a constant-bitrate stream indistinguishable from randomness. That's pretty much the gold standard.
(Of course, that still only encrypts content, not metadata. You can encrypt a phone call in such a way that a watcher gets mathematically zero information about what's being said, but the watcher still sees who is calling whom, when, and for how long. Hiding that is much harder.)
Rather than defining at the protocol level "insert comfort noise here" at the compression level you get bitstream level "I donno what this stream is at a higher level, but replace the next 1000 bits with zeros".
That's if you do simple sampling. I donno about weird higher level vocoders. I think you could create a constant bit rate vocoder that really is constant. But it'll likely be uncompressible if its a good one because a vocoder basically is a compressor that's specifically very smart about human speech input. If your vocoder output is compressible its not a good one.
I think if you replaced your compression step with run it thru a constant rate vocoder you'd get what you're looking for. Probably.