[FFmpeg-devel] [PATCH 2/3] decklink: new option 'format' to set video format by fourCC

Marton Balint cus at passwd.hu
Thu Mar 16 22:54:39 EET 2017

On Thu, 16 Mar 2017, Nicolas George wrote:

> Le sextidi 26 ventôse, an CCXXV, Matthias Hunstock a écrit :
>> I did not find a comparable option for another device in libavdevice,
>> "format" was the initial suggestion of Marton. This is at least
>> consistent with the existing "list_formats" option.
> I do not know what the option does, and therefore can not propose a
> better name.

It selects video standard, field order and frame rate, these fourcc-s are 
defined in the BlackMagic SDK. Example: 'Hp50'  - HD 1080p50 format.

> All I know is that we decided not to build an inconvenient
> infrastructure to avoid the collision between global, format, codecs
> options, at the cost of having to be careful when adding said options.
> This is exactly one of these cases: "format" can be added as a global
> option, as a ffmpeg.c option or anything else, because it is very
> generic.

Then the next guy should worry about this who wants to add a "format" 
option :)

The argument you made is true for a lot of other generic strings, such as 
"video_format" or "standard", so if I really want to make sure I don't use 
generic option names, I guess I will end up with a prefixed option name, 
such as bm_format. Only a few codecs/demuxers/devices do that.

So overall, I am not sure it's worth losing the consistency (using a 
prefixed option name, where almost all other option names are 
non-prefixed), but I don't really mind either way if we use bm_format 


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