[Libav-user] Channel mapping with amerge filter

Kerry Loux louxkr at gmail.com
Fri May 29 23:44:59 EEST 2020

On Fri, May 29, 2020, 1:46 PM Nicolas George <george at nsup.org> wrote:

> Kerry Loux (12020-05-29):
> > Thanks Nicholas. I was able to get it to work using the method you
> > described.
> Good to ear.
> > Actually, I had tried it earlier, but I struggled  because I was passing
> > invalid channel layouts to my src buffer filters. My mistake was that I
> > expected av_get_channel_layout_string() to produce values suitable for
> > passing as a "channel_layout" option to my buffer filters.
> That is worrying, I think they should be compatible. Do you remember
> which particular channel layout caused a problem?

Yes, AV_CH_FRONT_LEFT is an example. The returned string is something like
"1 channels (FL)." I had to extract only the parenthetical portion in order
to avoid an "invalid argument" error when calling avfilter_init_str().

> But you do not need it for this case, you can just print the channel
> layout as an integer.
> I forgot to add:
> If you need to change the order of the channels afterwards, the filter
> pan is there for that.
> Regards,
> --
>   Nicolas George
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