[FFmpeg-devel] [PATCH] metadata conversion API

Baptiste Coudurier baptiste.coudurier
Tue Mar 3 23:20:47 CET 2009

On 3/3/2009 2:05 PM, Michael Niedermayer wrote:
> On Tue, Mar 03, 2009 at 09:35:09PM +0000, Robert Swain wrote:
>> 2009/3/3 Michael Niedermayer <michaelni at gmx.at>:
>>> On Mon, Mar 02, 2009 at 06:25:30PM -0800, Baptiste Coudurier wrote:
>>>> I however volunteer to add key/value as char* options to AVFormatContext
>>>> and AVCodecContext and use them.
>>> You said that already but there is no relation between that and such validity
>>> checks, its not going to solve this problem.
>> OK, so maybe this is off topic for this thread.
>>> Things added to svn have to be justified and their advantages and
>>> disadavatanges weighted against each other. Also once a technical discussion
>>> happened its the decission of the maintainer(s). Or in exceptional
>>> circumstances a vote (or consensus for thouse prefering the terminology)
>>> overriding the maintainer.
>>> The arguments brought forth so far in favor of it, where that you want to
>>> export ".mov/width" with a value that could be scaling or croping. And that
>>> some advanced users may be able to make more sense out of it then we. And
>>> that you prefer not to export the croping information in the existing
>>> fields for this puprose.
>>> And you want to export a field (whichs name you have not revealed yet)
>>> that only has 2, 4 and 8 as valid values.
>>> Have i missed some? I remember alot of flaming and trolling and some
>>> unsuccessfull attempts at provocating me but little actual discussion
>>> about it.
>>> The arguments against, being a roughly 10x increase in memory consumtion,
>>> similar or worse increase in cpu consumtion for access and the loss of a
>>> common set of parameters for codecs. Each could have their own flag to
>>> enable b frames ...
>> The CPU loss should be minimal and it's only a set up cost. How many
>> cycles are really spent on option parsing?
> we directly access fields from AVCodecContext currently just try
> grep avctx libavcodec/*.c | grep -v av_log
> there are over 5000 matches
> i do not want to replace 5000 single instruction reads with 5000 function
> calls doing a search through a table of strings.
> Especially considering that i dont see what we would gain by this

I don't see how this relates to using char */char * as options, you can
set AVCodecContext fields if you want.

Although almost every codec has its own context anyway, point is to
factorize when it's actually needed and not by principle.

>> Also, we can still enforce
>> some sort of option naming consistency.
> I cant even enforce some decission about where to store the croping
> information now. And i am listed as maintainer of mov

Well you share maintainership, and please stop saying this, it is not
true, if you want to store croping into something actually used, I
already said you were free to do so.

Please don't focus on this "width" thing, this might apply to any
information people find useful.


Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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FFmpeg maintainer                                  http://www.ffmpeg.org

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