[FFmpeg-devel] [PATCH 11/15] lavc/videotoolbox: call VTRegisterSupplementalVideoDecoderIfAvailable

[Ridley Combs]

> On Nov 14, 2021, at 02:41, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> 
> On Sun, Nov 14, 2021 at 3:40 AM Ridley Combs <rcombs at rcombs.me <mailto:rcombs at rcombs.me>> wrote:
>> 
>> 
>> 
>>> On Nov 13, 2021, at 18:38, Marvin Scholz <epirat07 at gmail.com> wrote:
>>> 
>>> On 13 Nov 2021, at 22:09, rcombs wrote:
>>> 
>>>> This is required for VP9 to work.
>>>> ---
>>>> libavcodec/videotoolbox.c | 7 +++++++
>>>> 1 file changed, 7 insertions(+)
>>>> 
>>>> diff --git a/libavcodec/videotoolbox.c b/libavcodec/videotoolbox.c
>>>> index 18cc589d2a..0666446dbd 100644
>>>> --- a/libavcodec/videotoolbox.c
>>>> +++ b/libavcodec/videotoolbox.c
>>>> @@ -32,6 +32,7 @@
>>>> #include "h264dec.h"
>>>> #include "hevcdec.h"
>>>> #include "mpegvideo.h"
>>>> +#include <Availability.h>
>>>> #include <TargetConditionals.h>
>>>> 
>>>> #ifndef kVTVideoDecoderSpecification_RequireHardwareAcceleratedVideoDecoder
>>>> @@ -864,6 +865,12 @@ static int videotoolbox_start(AVCodecContext *avctx)
>>>>        break;
>>>>    }
>>>> 
>>>> +#ifdef __MAC_10_11
>>>> +    if (__builtin_available(macOS 10.11, *)) {
>>>> +        VTRegisterSupplementalVideoDecoderIfAvailable(videotoolbox->cm_codec_type);
>>>> +    }
>>>> +#endif
>>>> +
>>> 
>>> The VTRegisterSupplementalVideoDecoderIfAvailable is available since macOS 11 according to the
>>> header annotations:
>>> 
>>> VT_EXPORT void VTRegisterSupplementalVideoDecoderIfAvailable( CMVideoCodecType codecType ) API_AVAILABLE(macosx(11.0)) API_UNAVAILABLE(ios, watchos, tvos);
>>> 
>>> I guess you meant to check for macOS 11 here but accidentally used 10.11?
>> 
>> Ah, good catch! Fixed.
>> 
>>> 
>>> Additionally a more reliable/correct way for the SDK preprocessor check would be:
>>> 
>>> #if (!TARGET_OS_IPHONE && MAC_OS_X_VERSION_MAX_ALLOWED >= 110000)
>> 
>> How's this, using AvailabilityMacros.h?
>> 
>> #if defined(MAC_OS_VERSION_11_0) && !TARGET_OS_IPHONE && (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0)
>> 
> 
> MAX_ALLOWED seems like the wrong variable to use for me. Shouldn't
> this be MAC_OS_X_VERSION_MIN_REQUIRED (or, both), so that I can still
> target 10.15 or whatever with -mmacosx-version-min=10.15 without
> linking in unavailable functions?

The calls are behind __builtin_available, so they'll be weak-linked and only execute on macOS versions that include the relevant functions. MAX_ALLOWED is meant to indicate the latest version you want to even weakly link functions from (it doesn't actually mean the maximum supported version).

> 
> - Hendrik
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