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lavc/videotoolboxenc: better compat_keys docs

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Added more specific docs about when to use compat_keys, and how to
add new constants.

Signed-off-by: Rick Kern <kernrj@gmail.com>
This commit is contained in:
Rick Kern 2023-05-20 11:35:51 -04:00
parent efdc6e8200
commit 902c949d30
1 changed files with 13 additions and 3 deletions
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16
libavcodec/videotoolboxenc.c
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@ -64,9 +64,19 @@ typedef OSStatus (*getParameterSetAtIndex)(CMFormatDescriptionRef videoDesc,
int *NALUnitHeaderLengthOut);
/*
* Keys that are not present in all versions of VideoToolbox need to be
* accessed from compat_keys, or it will cause compiler errors when compiling
* for older OS versions.
* Symbols that aren't available in MacOS 10.8 and iOS 8.0 need to be accessed
* from compat_keys, or it will cause compiler errors when compiling for older
* OS versions.
*
* For example, kVTCompressionPropertyKey_H264EntropyMode was added in
* MacOS 10.9. If this constant were used directly, a compiler would generate
* an error when it has access to the MacOS 10.8 headers, but does not have
* 10.9 headers.
*
* Runtime errors will still occur when unknown keys are set. A warning is
* logged and encoding continues where possible.
*
* When adding new symbols, they should be loaded/set in loadVTEncSymbols().
*/
static struct{
CFStringRef kCVImageBufferColorPrimaries_ITU_R_2020;