On 2018-01-07 00:48, Gyan Doshi wrote:
On 1/7/2018 12:38 PM, Jim DeLaHunt wrote:
Those examples lack a `-f image2` option. I would expect that option
to be there; after all, isn't the image2 format exactly what this
section is trying to explain?
FFmpeg probes the input to determine its format. Adding the `-f`
option for an input forces the use of that demuxer e.g.
with a MKV renamed to MP4, running
ffmpeg -i in.mp4
will still result in FFmpeg recognizing it as a Matroska file.
but
ffmpeg -f mp4 -i in.mp4
will force the MP4 demuxer, and FFmpeg will throw an error.
Fair enough for FFmpeg in general.
And the term "demuxer" may be complicating things. The documentation for
`image2` describes it as a "demuxer"[1]. But elsewhere, I think the
FFmpeg documentation describes the operation of extracting multiple
still frames from a video as "demuxing"[2][4], and the complementary
operation of merging multiple still frames files into a video as
"muxing"[3]. I'm not sure what to make of that.
Maybe `image2` should actually be described as a "muxer"?
But my question is about the examples from section 20.9.1 Examples[1],
documenting the `-f image2` option. The input format is not something like:
ffmpeg -i in.mp4
It is a template for filenames of still images:
ffmpeg -i 'img-%03d.jpeg' out.mkv
So, for the case when we use ffmpeg to merge still image files into a
video file, should the `-f image2` option be required? And /in this
section/, which examples illustrating the use of the `-f image2` option,
is it really correct that the examples do not include `-f image2`?
[1] http://ffmpeg.org/ffmpeg-all.html#image2-1
[2] http://ffmpeg.org/ffmpeg-all.html#Detailed-description
[3] http://ffmpeg.org/ffmpeg-all.html#Demuxers
[4] http://ffmpeg.org/ffmpeg-all.html#Muxers
[5] http://ffmpeg.org/ffmpeg-all.html#Examples-6
Thanks,
—Jim DeLaHunt, Vancouver, Canada
--
--Jim DeLaHunt, [email protected] http://blog.jdlh.com/ (http://jdlh.com/)
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