[FFmpeg-user] current ffmpeg creates shortened audio stream when filter amix

S Andreason sandreas41 at gmail.com
Wed Oct 2 01:11:09 EEST 2019

Moritz Barsnick wrote:
> Hi Stewart,
> On Mon, Sep 30, 2019 at 12:48:31 -0700, S Andreason wrote:
>> Moritz Barsnick wrote:
>>> On Sun, Sep 29, 2019 at 10:38:33 +0200, Paul B Mahol wrote:
>>> Stewart, it helps if you leave away the parts of the video filter which
>>> aren't relevant to the issue (assuming you tried leaving them away on
>>> your side first), to make the command line easier to read.
>>> Also, it helps to explictly mark inputs and outputs in the
>>> filter_complex chains, to make sure they do what you intend them to do.
>>> (Implicit is for heros. I'm not one of them. ;-))
>> Yes I removed parts one or two at a time and tried only one or the other
>> of the audio filters to narrow it down.
>> I left out 90-95% of all the other inputs and drawtext, but left one in
>> so the crop-size flow was unchanged.
>> I didn't realize I left in a font reference until Paul asked for the
>> input files, then I had to choose whether to rewrite the reported
>> command line, or just provide the files.
>> Thank you very much for showing the right way to mark all inputs and
>> outputs. Somehow all my googling and reading of manuals failed to cover
>> that bit, or I didn't make the leap to understanding it. I didn't
>> realize [0:a] was the solution to [0:1] for example.
> Nice. Does this mean it solved your issue though? I wasn't sure that
> would be the case.

Yes the audio question is solved. I've learned how to use [0:a] instead 
of [0:1] or leaving it blank.

> Feel free to answer to the list instead of myself, in case you want
> more remarks or corrections (may not have been the case here). ;-)
Oh no. None of my replies went to the list...
I just hit reply and forgot to check that field.
That was not my intention.

When Paul said it shouldn't work, I replied:
When I started with one filter-complex, I could not guess how to get it 
working, and splitting the audio out to be separate actually solved it, 
and it worked, on the older version of ffmpeg.

This month long video project has finally finished getting rendered and 
uploaded to youtube.


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