[FFmpeg-devel] [PATCH] AVFoundation: Add -pixel_format option

[Thilo Borgmann]

Am 11.05.14 19:34, schrieb Carl Eugen Hoyos:
> sfan5 <sfan5 <at> live.de> writes:
> 
>>>> +    { AV_PIX_FMT_BGRA, kCVPixelFormatType_32BGRA },
>>> This should be AV_PIX_FMT_BGR0: The camera cannot
>>> record an alpha channel, the fourth channel is (or at
>>> least can be) 0, so it should be ignored.
>>> Same for the other 32 bit rgb formats.
>>
>> Isn't AVFoundation a generic API for video sources? 
>> (not only cameras)
>> There might be other devices that can record RGBA.
> 
> I can't really answer this but since AVFoundation 
> provides transparent images for 32 bit RGB it has 
> to be mapped to RGB0 to work at all.
> (If a user ever protests that his alpha channel 
> disappears, we will have to find a solution.)
> 
>>> Right now, if I specify a pixel format that does not
>>> work (like gray) FFmpeg prints many error messages
>>> but does not quit. Can you reproduce this?
>>> The expected behaviour imo is to quit if a pixel
>>> format that does not work is requested.
>>
>> I can reproduce this, but I am not sure which approach 
>> one would to take to fix this.
> 
> I cannot really test (I only borrowed a Mac for the quick 
> test before) but I would expect that some function call 
> returns an error if a pixel format that is not supported 
> is requested.

_Maybe_ the device can be queried for available/valid pixel formats.

-Thilo