[FFmpeg-devel] Animated GIF support

[Paul B Mahol]

On 12/19/12, Don Moir <donmoir at comcast.net> wrote:
> ----- Original Message -----
> From: "Vitaliy Sugrobov" <vsugrob at hotmail.com>
> To: <ffmpeg-devel at ffmpeg.org>
> Sent: Sunday, August 12, 2012 9:15 PM
> Subject: [FFmpeg-devel] Animated GIF support
>
>> Hi. I would like to participate in development of animated gif decoding
>> support.
>> Actually i've already implemented this feature by adding gif demuxer and
>> slightly changing
>> existing gif decoder, but it is not complete yet. There is a problem with
>> variable delay between
>> frames in gif: i cannot make it work. I tried to set time base via
>> avpriv_set_pts_info (1 for numerator, 25 for denominator) in my demuxer's
>> gif_read_header(),
>> at the same time in gif_read_packet() i set proper pts, dts and duration
>> for each succesive packet.
>> But it doesn't work: conversion from gif to any kind of video gives me
>> output with
>> 25 frames per second rate and constant delay between frames. Please point
>> me in the right direction.
>
> I don't use ffmpeg for gif's but did a comparison of latest gif patches and
> found some problems with ffmpeg animtated gif support.
>
> Several had no transparency which should have been transparent and hears a
> couple samples of that:
>
> http://sms.pangolin.com/temp/chompy.gif  - shows gray background
>
> http://sms.pangolin.com/temp/cool.gif  - shows black background
>
> This one gets transparency right but seems to have the wrong delay. The
> delay value I get is 15 which is 150ms. With ffmpeg its way
> to fast.
>
> http://sms.pangolin.com/temp/crazy.gif  - 2 frames and animates too fast
>
> This one caused me to crash in avcodec_decode_video2:
>
> http://sms.pangolin.com/temp/heart.gif
>
> I have many more gifs that may cause problems and if you decide to fix the
> above I will test it some more. All of the above
> displayed normally outside of ffmpeg.

Please open bug report for such problems. At least I can not keep
track of all mailing list threads.