[FFmpeg-user] amix: Hard limit for number of inputs?

Paul B Mahol onemda at gmail.com
Tue Jul 16 19:36:23 EEST 2019

On 7/16/19, Paul B Mahol <onemda at gmail.com> wrote:
> On 7/16/19, Reino Wijnsma <rwijnsma at xs4all.nl> wrote:
>> On 16-7-2019 15:36, Paul B Mahol <onemda at gmail.com> wrote:
>>> On 7/16/19, Reino Wijnsma <rwijnsma at xs4all.nl> wrote:
>>>> About 7 years ago I've used Audacity to assemble the soundtrack of the
>>>> videogame No One Lives Forever 2. See
>>>> https://www.youtube.com/watch?v=4Y3aKcQ0HK4 for example.
>>> Why you use adelay?
>>> Perhaps you want acrossfade filter instead, or even better concat
>>> filter.
>> I can't use these filters. Have a look at the Youtube video please.
>> I wish it was a simple matter of just concatenating all segments, but it
>> isn't, because the segments don't align perfectly.
>> Each segments has to start at a very specific time.
>> Then it's a matter of mixing everything at full volume(!), so there's no
>> fading involved at all.
> acrossfade can just join it with nofade curve, which basically disables
> fading.
>> Do you happen to know why ffmpeg reports a completely wrong duration?
>> Related question/suggestion:
>> It's really cumbersome to always having to specify the delay for all(!)
>> channels: [1]adelay=158792S|158792S[E2];
>> How about a default behaviour where specifying an amount of
>> milliseconds/samples once(!) applies to all channels:
>> [1]adelay=158792S[E2];
>> And if you want a specific delay for another channel, then you can do so
>> as
>> is already possible.
>> This would make my commandline a lot shorter!
> The thing with amix is that by reducing volume by mixing and adding it
> back with volume,
> you basically loose quality. It is more obvious with float sample
> format then double one.
> Option could be added to amix filter to just sum samples as is.
> Also what ffmpeg version you are using?

Actually ffmpeg is behaving correctly, your [29]adelay is missing one S.

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