[FFmpeg-devel] [PATCH 2/2] MxPEG decoder

Michael Niedermayer michaelni
Sat Nov 13 02:24:04 CET 2010

On Thu, Nov 11, 2010 at 02:16:27AM +0300, Anatoly Nenashev wrote:
> On 10.11.2010 18:28, Michael Niedermayer wrote:
>> On Wed, Nov 10, 2010 at 06:08:47PM +0300, Anatoly Nenashev wrote:
>>> [...]
>>> If to read more than 16 byte at once then it is required additional
>>> operations of memcpy and memmove.
>>> For example. If I read buffer of 256 bytes in which audio packet
>>> available in position 10 and size 100 then I need
>>> to copy data of size 100-10=90 in new audio packet and move data of size
>>> 256-100=156 in internal buffer. I think this may reduce the performance.
>> you dont need to move it.
>> and the overhead of all your code executed once every 16 bytes will reduce
>> performance more than an occasional memcpy(). That said it can be done
>> without memcpy by accessing the internal buffer but iam not suggesting this
>> to be done.

There are many ways to implement this, one simple one is
you have a internal buffer
you read into it
you return AVPackets that point into this buffer and have destruct=NULL

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Breaking DRM is a little like attempting to break through a door even
though the window is wide open and the only thing in the house is a bunch
of things you dont want and which you would get tomorrow for free anyway
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