On Wed, May 22, 2024 at 12:37:37PM +0200, Stefano Sabatini wrote: > On date Sunday 2024-05-05 22:04:36 +0100, Andrew Sayers wrote: > > I'm still travelling, so the following thoughts might be a bit > > half-formed. But I wanted to get some feedback before sitting down > > for a proper think. > [...] > > > > I've also gone through the code looking for edge cases we haven't > > > > covered. > > > > Here are some questions trying to prompt an "oh yeah I forgot to mention > > > > that"-type answer. Anything where the answer is more like "that should > > > > probably be rewritten to be clearer", let me know and I'll avoid > > > > confusing > > > > newbies with it. > > > > > > > > > > > av_ambient_viewing_environment_create_side_data() takes an AVFrame as > > > > its > > > > first argument, and returns a new AVAmbientViewingEnvironment. What is > > > > the > > > > context object for that function - AVFrame or > > > > AVAmbientViewingEnvironment? > > > > > > But this should be clear from the doxy: > > > > > > /** > > > * Allocate and add an AVAmbientViewingEnvironment structure to an > > > existing > > > * AVFrame as side data. > > > * > > > * @return the newly allocated struct, or NULL on failure > > > */ > > > AVAmbientViewingEnvironment > > > *av_ambient_viewing_environment_create_side_data(AVFrame *frame); > > > > I'm afraid it's not clear, at least to me. I think you're saying the > > AVFrame is the context because a "create" function can't have a > > context any more than a C++ "new" can be called as a member. But the > > function's prefix points to the other conclusion, and neither signal > > is clear enough on its own. > > No, what I'm saying is that in some cases you don't need to think in > terms of contexts, in this case there is no context at all, the > function takes a frame and modify it, and returns the ambient > environment to be used by the following functions. This should be very > clear by reading the doxy. There is no rule dictating the first param > of each FFmpeg function should be a "context".
I'm still writing up a reply to your longer feedback, but on this topic... This function is in the "av_ambient_viewing_environment" namespace, and returns an object that is clearly used as a context for other functions. So saying "stop thinking about contexts" just leaves a negative space and a bad thing to fill it with (confusion in my case). I've found it useful to think about "receiving" vs. "producing" a context: * avcodec_alloc_context3() produces a context, but does not receive one * sws_init_context() receives a context, but does not produce one * av_ambient_viewing_environment_create_side_data() receives one context, and produces another How about if the document mostly talks about functions as having contexts, then follows it up with something like: There are some edge cases where this doesn't work. <examples>. If you find contexts a useful metaphor in these cases, you might prefer to think about them as "receiving" and "producing" contexts. ... or something similar that acknowledges contexts are unnecessary here, but provides a solution for people that want to use them anyway. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".