[FFmpeg-user] Mix a video with an audio file

[Paul B Mahol]

On 1/19/20, Michael Koch <astroelectronic at t-online.de> wrote:
> Am 19.01.2020 um 21:56 schrieb Paul B Mahol:
>> On 1/19/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>> Am 19.01.2020 um 21:01 schrieb Paul B Mahol:
>>>> On 1/19/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>>>> Hello,
>>>>>
>>>>> I've just found a problem that can be reproduced as follows:
>>>>>
>>>>> Step 1: Make a 6 seconds test video with 1kHz tone. The file is ok when
>>>>> played.
>>>>>
>>>>> ffmpeg -f lavfi -i testsrc2=size=vga -f lavfi -i sine=1000 -t 6 -y
>>>>> video.mp4
>>>>>
>>>>>
>>>>> Step 2: Make a 10 seconds audio file with silence and a short 3kHz tone
>>>>> at t=3s. The file is ok when played.
>>>>>
>>>>> ffmpeg -f lavfi -i "sine=3000:duration=0.1" -af adelay=3000,apad -t 10
>>>>> -y audio.wav
>>>>>
>>>>>
>>>>> Step 3: Combine both files into one video, and the audio sources shall
>>>>> be mixed:
>>>>>
>>>>> ffmpeg -i video.mp4 -i audio.wav -filter_complex
>>>>> "[0:a][1:a]amix=weights='1.0 1.0'" -shortest -y out.mp4
>>>>>
>>>>> The output video has the correct length 6s, but I don't understand why
>>>>> the 1kHz tone disappears after 4s and the last 2s are silence.
>>>>>
>>>>> The console output is below.
>>>> Can not reproduce using nut container.
>>> When I change the output filename to out.nut, then it works as expected
>>> (but with terrible image quality). Why doesn't it work with mp4 output?
>> Use different video encoder. Who knows?
>
> When I add -c:v mpeg4 then it works fine.
> When I add -c:v libx264 then the audio output is 2s too short.
> Is it a bug, or is something wrong with my command line?
>

Dunno.

> Michael
>
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