On Wed, Nov 14, 2018 at 7:00 AM Song, Ruiling <ruiling.s...@intel.com> wrote:
> > > > -----Original Message----- > > From: ffmpeg-devel [mailto:ffmpeg-devel-boun...@ffmpeg.org] On Behalf Of > > Mark Thompson > > Sent: Sunday, November 11, 2018 9:55 PM > > To: ffmpeg-devel@ffmpeg.org > > Subject: Re: [FFmpeg-devel] [PATCH 2/4] lavfi/opencl: Handle overlay > input > > formats correctly. > > > > On 29/10/18 05:56, Ruiling Song wrote: > > > The main input may have alpha channel, we just ignore it. > > > > This doesn't ignore it - it leaves it uninitialised in the output, so a > YUVA or GBRAP > > output will never write to the A plane. I don't think that's what > you're intending. > What I wanted to say is ignoring main input alpha channel. > The question is what the user would expect the result alpha channel > contains? > I don't have a clear answer to it, so I just keep it uninitialized. The s/w overlay filter does this to produce the output alpha: main_alpha += (1-main_alpha) * overlay_alpha Better to keep it consistent, IMHO. Gyan _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
