[FFmpeg-user] Create slideshow with ffmpeg from still images

Paul B Mahol onemda at gmail.com
Mon Jul 29 19:08:12 CEST 2013

On 7/29/13, thljcl <jiachielee at live.com> wrote:
> Yes, I'm aware of the fact that ffmpeg can be used to concatenate videos
> Physical concatenation protocol.
> Allow to read and seek from many resource in sequence as if they were a
> unique resource.
> A URL accepted by this protocol has the syntax:
>  	concat:URL1|URL2|...|URLN
> where URL1, URL2, ..., URLN are the urls of the resource to be concatenated,
> each one possibly specifying a distinct protocol.
> For example to read a sequence of files `split1.mpeg', `split2.mpeg',
> `split3.mpeg' with ffplay use the command:
>  	ffplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg
> Note that you may need to escape the character "|" which is special for many
> shells.
> But I can make my own choice to use the tools I prefer, can I not?

Yes, but not telling rest of world your sub-optimal solution.

Also there are better ways to concatenate videos, but it appears you are
aware of only this one.

> With regards to reporting bugs to ffmpeg developers, I do not in this case
> discover a bug, so to speak. If it sounds like a bug to you; suite yourself
> to report it. I'm sure that you can test it to find the bugs yourself.
> Bear in mind, frame rate conversion from one constant frame rate to another
> always involves adding or dropping frames. As users, we might not know the
> algorithms behind the video filter "fps"; that's why I specifically perform
> a number of tests to find out how it decides which frames it adds or drops.
> I would consider the frame rate conversion is "flawed" if such a condition
> is true: the conversion process is not reversible. Well, allows me to
> elaborate further.
> If the original source is of the frame rate of lower frame rate, when its
> frame rate is to be converted to higher frame rate, it would involve the
> duplication of frames; of course the question of which frames would be
> duplicated depends on the algorithms designed by the developers. When the
> video of higher frame rate with duplicated frames undergoes frame rate
> conversion so that the output would have the original frame rates, only
> duplicated frames would be dropped. Even though the length of the videos
> would change due to frame rate conversion, repeated conversion from one to
> another and vice versa would not change the video length for a specific
> frame rate. Of course, if the source of higher frame rate with no duplicated
> frames undergoes frame rate conversion to achieve lower frame rate, such a
> process is irreversible, as expected.
> Based on my own tests, ffmpeg passes my expectation of how frame rate
> conversion should be handled. That's why I do not discover a bug. However,
> if you find bugs from my experience, feel free to report it and publish it.
> I have to say that the basic idea behind the duplication of frames to create
> a slideshow involves a feature in ffmpeg which is frame rate conversion. In
> effect, we use frame rate conversion algorithms to cause ffmpeg to duplicate
> frames for us, instead of manually copying frames to create a slideshow.
> I'm not absolutely sure that my way of creating a slideshow is particularly
> good or superior, that's why I did not attempt to edit the ffmpeg wiki.
> No, it's not meant for propagating my views of world. In fact, similar
> questions have been asked before at http://bit.ly/13rjKL3 and
> http://bit.ly/1cgluyH. But while I believe that my experience may be helpful
> to somebody, it does not directly answer their questions. Speaking of
> questions the users may ask, it's indeed a question. It is a question I
> would ask myself as well as other possibly much more skillful users of
> ffmpeg. I gave my "workaround". But in no way I suggested that somehow I
> gave a perfect answer. If I sound like such, I apologize in advance.
> Presumably, somebody else may have better answers for what I saw or what I
> want to achieve. Possibly, my understanding of how ffmpeg works is
> misguided.
> That's why I specifically try to extract all the original non-duplicated
> frames from the created slideshow, which is successful, I have to say.

Have you read documentation of fps filter?
Did you tried changing its parameters?

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