[Libav-user] GIF API access
Carl Eugen Hoyos
ceffmpeg at gmail.com
Mon Mar 6 10:58:03 EET 2017
2017-03-06 5:56 GMT+01:00 Gustav González <xtingray at gmail.com>:
> 2017-03-05 20:46 GMT-05:00 Carl Eugen Hoyos <ceffmpeg at gmail.com>:
>> 2017-03-06 1:44 GMT+01:00 Gustav González <xtingray at gmail.com>:
>> > So, my next challenge is to low the size of the frames to finish my
>> > implementation. Any hint?
>> Yes, please see my last two emails in this thread.
To repeat and evaluate:
Current FFmpeg does not support RGB24 in gif.
I don't know if you are using other software or an
old version of FFmpeg, in both cases, you cannot
get support here.
This is the first issue you have to solve: Either update
to current FFmpeg or get support somewhere else.
And yes, you have guessed correctly that PAL8
ensures a smaller file size.
> Getting back to the libswscale approach, I was trying to transform the
> QImage sequence into AVFrame variables:
> QImage image(path_to_image);
> AVPicture picture;
> avpicture_alloc(&picture, PIX_FMT_RGB32, w, h);
> memcpy(picture.data, image.bits(), w*h*4);
Unrelated: I suggest you try to avoid the memcpy().
> QVector<int> strides(image.height(), image.bytesPerLine());
> struct SwsContext *sws_context = sws_getContext(w, h, PIX_FMT_RGB32,
> w, h, AV_PIX_FMT_RGB8, SWS_BICUBIC, NULL, NULL, NULL);
It is not so easy to get palettised data. It is a two-step process
involving the paletteget and paletteuse filter, see for example:
Please try with ffmpeg (the application) first to find out if
this is really worth the effort (and if you need to program
something instead of calling the application).
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