On 12/16/2017 04:19 PM, Wang Bin wrote: > 2017-12-16 15:33 GMT+08:00 Xiaolei Yu <dreifachst...@gmail.com>: >> On 12/16/2017 02:07 PM, Wang Bin wrote: >>> 2017-12-16 2:52 GMT+08:00 wm4 <nfx...@googlemail.com>: >>>> On Fri, 15 Dec 2017 15:02:44 +0800 >>>> wbse...@gmail.com wrote: >>>> >>>>> From: wang-bin <wbse...@gmail.com> >>>>> >>>>> 1. a cvpixelbuffer backed by iosurface can always be converted to an >>>>> opengl texture, using CGLTexImageIOSurface2D for macOS, and undocumented >>>>> api texImageIOSurface(which is internally used by public api >>>>> CVOpenGLESTextureCacheCreateTextureFromImage) for iOS4.0+. >>>>> 2. enabling the attribute can slow down decoding speed a lot. I tested >>>>> many video clips on my macbook air. for example: ffmpeg -ss 00:00:00 -t >>>>> 00:03:00 -hwaccel videotoolbox -an -i big_buck_bunny_1080p_h264.mov -f >>>>> null ->/dev/null, result with the attribute >>>>> enabled: frame= 2082 fps= 85 q=-0.0 Lsize=N/A time=00:03:00.00 >>>>> bitrate=N/A speed=7.34x >>>>> disabled: frame= 2031 fps=104 q=-0.0 Lsize=N/A time=00:03:00.00 >>>>> bitrate=N/A speed=9.22x >>>>> --- >>>>> libavcodec/videotoolbox.c | 5 ----- >>>>> 1 file changed, 5 deletions(-) >>>>> >>>>> diff --git a/libavcodec/videotoolbox.c b/libavcodec/videotoolbox.c >>>>> index 9d2f0afa20..24631684d7 100644 >>>>> --- a/libavcodec/videotoolbox.c >>>>> +++ b/libavcodec/videotoolbox.c >>>>> @@ -664,11 +664,6 @@ static CFDictionaryRef >>>>> videotoolbox_buffer_attributes_create(int width, >>>>> CFDictionarySetValue(buffer_attributes, >>>>> kCVPixelBufferIOSurfacePropertiesKey, io_surface_properties); >>>>> CFDictionarySetValue(buffer_attributes, kCVPixelBufferWidthKey, w); >>>>> CFDictionarySetValue(buffer_attributes, kCVPixelBufferHeightKey, h); >>>>> -#if TARGET_OS_IPHONE >>>>> - CFDictionarySetValue(buffer_attributes, >>>>> kCVPixelBufferOpenGLESCompatibilityKey, kCFBooleanTrue); >>>>> -#else >>>>> - CFDictionarySetValue(buffer_attributes, >>>>> kCVPixelBufferIOSurfaceOpenGLTextureCompatibilityKey, kCFBooleanTrue); >>>>> -#endif >>>>> >>>>> CFRelease(io_surface_properties); >>>>> CFRelease(cv_pix_fmt); >>>> >>>> Does this have a negative effect on compatibility or performance? (In >>>> both cases I'm asking about the case when actually using GL rendering.) >>> >>> Disabling the attribute improves performance in my tests. I can not >>> find any document about these keys. What i know is the decoded >>> cvpixelbuffer is backed by iosurface, and the api to create texture >>> from iosurface is available since macOS10.6 >> >> Maybe you can add a flag to make them optional? >> They are documented at: >> https://developer.apple.com/documentation/corevideo/kcvpixelbufferopenglescompatibilitykey >> https://developer.apple.com/documentation/corevideo/kcvpixelbufferiosurfaceopengltexturecompatibilitykey >> >> Things may still work without them but I would like to follow the >> documentation whenever possible. And I think iOS DOES require the flag for >> those buffers to be consumed through GLES. >> > > Your links explain nothing. iOS does not need it as mentioned in the > patch. I tested on iphone4s+iOS9 and some new devices.
Will find time to test this week. VTDecompressionOutputCallback actually returns a CVImageBuffer and blindly casting it to a CVPixelBuffer is dangerous. I will test if the type ids of the output are affected with different key combinations. > >> Pure speculation here. GPU texture units usually require special memory >> layouts that may be suboptimal for the decoder. When these constraints are >> not met either the driver has to perform the conversion or you pay the >> penalty at access time. > > Not sure about memory layout. The fact is on mac the performance is > much better without it. No difference on ios. > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
