On Mon, Mar 14, 2016 at 03:38:52PM +0100, Thilo Borgmann wrote: > Am 14.03.16 um 13:56 schrieb Clément Bœsch: > > On Mon, Mar 14, 2016 at 01:46:52PM +0100, Thilo Borgmann wrote: > >> Am 14.03.16 um 11:22 schrieb Clément Bœsch: > >>> [...] > >>>> +./ffmpeg -f lavfi -i > >>>> nullsrc=s=100x100,coreimage=filter=CIQRCodeGenerator@@inputMessage=https\\\\\://FFmpeg.org/@@inputCorrectionLevel=H > >>>> -frames:v 1 QRCode.png > >>> > >>> remove ./ > >>> > >>> also, it's probably better to have 2 filters: one for usage as a source, > >>> and another one for filtering (coreimagesrc vs coreimage). > >> > >> I want to extend it later to allow the user to define an output size > >> avoiding > >> the need to have it defined by input iamge size. Then it could be used as > >> an > >> image source, too. However, I'll have to think about many more cases for > >> that to > >> work good. Thus I really want to do it as further work. > >> > >> Also, if we split out the generator category into coreimagesrc, the > >> following > >> would not work anymore without GPU-HOST transfer: > >> > >> coreimage=filter=boxblur@default#qrcode@whatever@somewhere > >> > >> Instead the user would have to use a complex filter: > >> > >> coreimagesrc=filter=qrcode@whatever [qr], > >> [v:0] coreimage=filter=boxblur@default [blur], > >> [blur][qr]overlay=somewhere [output] > >> > >> To do it without transfer then would require to allow coreimage to do > >> generators > >> like coreimagesrc - which would void the argument for a seperated src > >> because > >> complete feature duplication, don't you think? > >> > > > > If you can hold the picture into a CVPixelBuffer, you could use > > AV_PIX_FMT_VIDEOTOOLBOX, which make it possible to create one single > > apple filter per coreimage instance in the filtergraph. > > > > It's probably a cleaner design. You'll probably need a > > AV_PIX_FMT_VIDEOTOOLBOX to AV_PIX_FMT_RGBA (or whatever) convert filter > > (transparently in vf scale, or maybe simply a coreimage=torgba) > > Spec says: "A Core Video pixel buffer is an image buffer that holds pixels in > main memory." A more valid choice could be CVImageBuffer. >
You'll need a new pixel format then probably, but this makes me wonder why
we are casting CVImageBufferRef into CVPixelBufferRef in
lavc/videotoolbox...
> Anyway, the object itself should be retainable across filter instances, also
> as
> a CIImage object. The filter would also have to know about the complete filter
> chain to know if the image should be kept as CIImage object (probably in VRAM)
> for further processing or if it has to be transferred to the host... and where
> in the chain is the current instance? Did it correctly retain an image for
> this
> instance? What if an error occurs in between? Do we know that?
>
> There is just missing some work for making a nullsrc in before avoidable. The
> alternative might bring object conversion (PIX_FMT & toRGB filters?), much
> more
> complex code and filter graph parsing together with a distinct modularization
> with almost the same code. I see this much more error prone and way harder to
> debug and maintain. Once the user can specify an output size the existing code
> would already perfectly serve as an image source.
>
The filter negotiation is already present in lavfi which should already be
capable of inserting a scaling (convert) filter automatically where it
matters.
An AV_PIX_FMT_VIDEOTOOLBOX is simply a frame with data[3]=CVPixelBufferRef
so you can transmit them between filter instances. They are refcounted so
properly wrapped in AVFrame (see ff_videotoolbox_buffer_create())
> Sorry, I don't think it would be the better choice.
>
>
> >>>> +#define SafeCFRelease(ptr) { \
> >>>> + if (ptr) { \
> >>>> + CFRelease(ptr); \
> >>>> + ptr = NULL; \
> >>>> + } \
> >>>> +}
> >>>
> >>> please use do while(0) form
> >>
> >> I don't understand how do while(0) form could be applied here, please
> >> explain.
> >>
> >
> > #define SafeCFRelease(ptr) do { \
> > if (ptr) { \
> > CFRelease(ptr); \
> > ptr = NULL; \
> > } \
> > } while (0)
>
> I don't know why this is beneficial but I'll change it locally.
>
So
if (x)
SafeCFRelease(a);
else
SafeCFRelease(b);
can work.
--
Clément B.
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