[FFmpeg-devel] Animated GIF support

Paul B Mahol onemda at gmail.com
Thu Dec 20 01:55:31 CET 2012

On 12/20/12, Don Moir <donmoir at comcast.net> wrote:
> ----- Original Message -----
> From: "Paul B Mahol" <onemda at gmail.com>
> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> Sent: Wednesday, December 19, 2012 7:41 PM
> Subject: Re: [FFmpeg-devel] Animated GIF support
>> 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.
> Since I do not use ffmpeg for most image types and probably never well,
> consider this a public service that I at least spent some
> time testing it more completely. I don't wish to spend any more time on it,
> but if fixes are made I will test it. If someone wants
> to file bug reports then have at it. I think to often patches are made
> without complete testing.

So you are saying that gif animation support should be removed?

People are not perfect so expecting perfect code is pointless.

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