[Ffmpeg-devel] libavcodec h264 decoder

Måns Rullgård mru
Sat Dec 16 12:12:24 CET 2006

"michael benzon chua" <chibiakaii at gmail.com> writes:

> On 12/15/06, Loren Merritt <lorenm at u.washington.edu> wrote:
>> On Fri, 15 Dec 2006, michael benzon chua wrote:
>> > On 12/15/06, Stefan Gehrer <stefan.gehrer at gmx.de> wrote:
>> >
>> >> Interesting concept, but as soon as you use some real
>> >> cryptography instead of just toggling the sign I think the
>> >> bitstream size will increase as some seemingly random
>> >> coefficients will be harder to compress than what the encoder
>> >> outputs. Or am I missing something?
>> >
>> > I think this is the case as well. The size of the output .264 file
>> > increased when I changed the dct values. I'm hoping the effect
>> > isn't too significant, and that the encryption is still
>> > reversible.
>> The size of the .264 shouldn't change if you just toggle the
>> coefficient's sign, because sign isn't compressed.  Why do you want
>> to mess with the guts of the codec, rather than encrypting the whole
>> stream?
> Trying to figure out which is more efficient. The only alternative
> I've heard of to encrypting everything is encrypting the dct
> coefficients.

That doesn't answer the question why you don't want to encrypt the
entire stream.

M?ns Rullg?rd
mru at inprovide.com

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