On 12/8/2021 7:55 AM, Nicolas George wrote:
James Almer (12021-12-07):
This is an updated and rebased version of the API that was sent to this mailing
list about two years ago. It expands it with some new helpers, implements some
changes that allows further extensibility for new features down the line, and
finishes porting all missing modules and those introduced since 2019.
I see the concerns I raised last time have not been addressed:
(1) the ability to have a channel at a certain location several times;
(2) the ability to attach an arbitrary label to a channel or to a group
of channels;
(3) an API and syntax for the user to specify a particular channel.
(1) is necessary for the amerge filter: merge two stereo streams, you
get two FL and two FR.
(1) is also necessary for devices that can record several sources
simultaneously. IIRC, that is the case for the BlackMagick devices. If
your devices records a band from two stereo and three mono microphones,
we need two FL, two FR and three FC.
(2) and (3) are necessary consequences of (1).
I also have concerns with the signature of av_channel_description():
this is level 0 of string manipulation, we need to get past this. I
should post again about this in a separate thread.
What is wrong with it? All the functions returning a string in this API
use the same signature. You pass it a pre-allocated buffer and it's
filled with the string, truncating it if there's not enough space and
letting the user know about it.
I recall you were against dynamic allocation of the string, which the
user then had to free, so this was the alternative.
I could make it use a user provided AVBprint buffer instead of using one
internally, if you think that's better, but since you planned to replace
that with AVWriter i figured using AVBprint in the signature would mean
an eventual deprecation and removal.
Regards,
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