[FFmpeg-devel] [PATCH 0/4] User controllable padding

James Darnley james.darnley at gmail.com
Wed Jan 1 19:24:00 CET 2014

On 2014-01-01 13:46, Michael Niedermayer wrote:
> On Wed, Jan 01, 2014 at 01:01:24PM +0100, James Darnley wrote:
>> On 2013-12-30 20:16, James Almer wrote:
>>> -1 for default value, 0 for no padding. Muxers can and should clip the value if needed.
>>> Ideally look up the corresponding limit for both flac and id3v2.
>>> You need to keep the default of 8192 if there's no user provided value.
>>> Same with the value in the id3v2 patch.
>> Why should there be a "default value" value?  Why would different
>> formats have different defaults for a feature intended to do the same
>> thing on them all?
> different formats have different requirements. different
> recommanditions, differnt constraints due to compatibility with
> various software.
> Having per format defaults is the easy solution.
> If you want to change the default padding used by some format then
> theres the question if that breaks any software or hardware that reads
> that format. This would have to be tested ...
> but its a bit worse then that, even if for the current formats
> theres a common default that would work for all, a format added
> in the future might have different requirements, like the padding
> being a multiple of 12345
> also it might make sense to instead use private options for each
> muxer that supports this, as that way it would be clear which
> muxers support it and what is the valid range of padding for each
> format, as well as the default, its not clear if this or a common
> field in AVFormatContext is better

I'm not going to be adding something that prints out half a dozen more
lines (at present) in the help.  The option is supposed represent the
same thing for many formats.  We don't have separate -metadata options
for each muxer to tell the user what is possible and what is not.

> for AVFormatContext fields you need accessors though (for ABI compat),

I have no idea what you mean with this.  Searching shows that
MAKE_ACCESSORS() gives get and set functions but this is only used for a
few fields.  What did you want?

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