On 23.03.2018 18:42, Dan Dennedy wrote:
Do not forget to check libavutil version when adding more pixfmts.
One more question since I am not very familiar with the avformat / alpha
pipeline.
The AV_PIX_FMT_YUVA444P10LE uses 10bits for each chanel. So I cannot
easily create the alpha buffer like done for the other YUVA formats in
https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.c#L1391
Should I convert the 10bit alpha buffer to an 8 bit buffer ? Or convert
the whole frame to an 8 bit yuva format ? If yes, where should that be
done ? Not sure how to do this properly so some guidance would help.
Thanks in advance
jb
On Fri, Mar 23, 2018 at 6:31 AM Brian Matherly <[email protected]
<mailto:[email protected]>> wrote:
On 3/23/2018 2:47 AM, Jean-Baptiste Mardelle wrote:
> Hi all,
>
> In order to optimize performance, in the qtblend transition (in
the qt
> module), I try to detect if the top frame in the transition has
> transparency, and if it doesn't, instead of performing the
transition I
> just return the top frame.
>
> However currently, to check if a frame has transparency I use the
> following:
>
> if ( *format == mlt_image_rgb24a || mlt_frame_get_alpha( b_frame ) )
> {
> // The frame has an alpha channel
> }
>
> However, some YUV formats with alpha, like AV_PIX_FMT_YUVA444P10LE,
> don't obey these rules since the alpha buffer is not created.
I predict the problme is not in the qtblend transition. The problem is
probably that the avformat_producer is not creating the alpha channel.
Maybe the problem is that AV_PIX_FMT_YUVA444P10LE is not handled here:
https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.c#L1391
And/Or maybe it needs to be added here:
https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.c#L1184
> Shouldn't the alpha buffer be created by default for this
codecs, or is
> there any other way to detect that the frame has alpha?
>
> Thanks for your advice.
>
> You can find sample video files in this bug report:
> https://bugs.kde.org/show_bug.cgi?id=391963
>
> Regards
>
> Jean-Baptiste
~Brian
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