On Fri, Dec 17, 2021 at 01:04:19AM +0100, Marton Balint wrote: > > > On Thu, 16 Dec 2021, James Almer wrote: > > > Resending the first two patches only, since this is meant to > > show the implementation of one of the several suggestions made > > in the previous set that need to be discussed and hopefully > > resolved in a call. > > Can you push the full branch somewhere? > > > > > The proposals so far to extend the API to support either custom > > labels for channels are, or some form of extra user information. > > > > - Fixed array of bytes to hold a label. Simple solution, but > > the labels will have a hard limit that can only be extended > > with a major bump. This is what i implemented in this version. > > - "char *name" per channel that the user may allocate and the > > API will manage, duplicate and free. Simple solution, and the > > name can be arbitrarily long, but inefficient (av_strdup() per > > channel with a custom label on layout copy). > > - "const char *name" per channel for compile time constants, or > > that the user may allocate and free. Very efficient, but for > > non compile time strings ensuring they outlive the layout can > > be tricky. > > - Refcounted AVChannelCustom with a dictionary. This can't be > > done with AVBufferRef, so it would require some other form > > of reference counting. And a dictionary may add quite a bit of > > complexity to the API, as you can set anything on them. > > Until we have proper refcounting API we can make the AVBufferRef in > AVChannelLayout a void *, and only allow channel_layout functions to > dereference it as an AVBufferRef. This would mean adding some extra helper > functions to channel layout, but overall it is not unsolvable. > > The real question is that if you want to use refcounting and add helpers to > query / replace per-channel metadata, or you find the idea too heavy weight > and would like to stick to flat structs.
what is the advantage of refcounting for channel metadata ? is it about the used memory, about the reduced need to copy ? what kind of metadata and what size do you expect ? bytes, kilobytes, megabytes, gigabytes per channel ? what is the overhead for dynamic allocation and ref counting? that is at which point does it even make sense ? thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Nations do behave wisely once they have exhausted all other alternatives. -- Abba Eban
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