alt Hacker News> Having an extensible format and electing never to extend it seems pointless.
This proves OP analogy regarding USB-C. Having PNG as some generic container for lossless bitmap compression means fragmentation in libraries, hardware support, etc. The reason being that if the container starts to support too many formats, implementations will start restricting to only the subsets the implementers care about.
For instance, almost nobody fully implements MPEG-4 Part 3; the standard includes dozens of distinct codecs. Most software only targets a few profiles of AAC (specifically, the LC and HE profiles), and MPEG-1 Layer 3 audio. Next to no software bothers with e.g. ALS, TwinVQ, or anything else in the specification. Even libavcodec, if I recall correctly, does not implement encoders for MPEG-4 Part 3 formats like TwinVQ. GP's fear is exactly this -- that PNG ends up as a standard too large to fully implement and people have to manually check which subsets are implemented (or used at all).
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JPEG is no different. Only the decoder is specified. As long as the decoder decodes what you give it to the image you wanted to see, you can implement anything. This is how imgoptim/squash/aerate/dietJPG works. By (ab)using this flexibility.
Same is also true for the most advanced codecs. MPEG-* family and MP3 comes to my mind.
Nothing stops PNG from defining a "set of decoders", and let implementers loose on that spec to develop encoders which generate valid files. Then developers can go to town with their creativity.
I honestly don't see an issue with the mpeg-4 example.
Regarding the potential for fragmentation of the png ecosystem the alternative is a new file format which has all the same support issues. Every time you author something you make a choice between legacy support and using new features.
From a developer perspective, adding support for a new compression type is likely to be much easier than implementing logic for an entirely new format. It's also less surface area for bugs. In terms of libraries, support added to a dependency propagates to all consumers with zero additional effort. Meanwhile adding a new library for a new format is linear effort with respect to the number of programs.
I never once in 25 years encountered an issue with an mp4 Container that could Not be solved by installing either the divx or xvid codec. And I extensively used mp4's metatdat for music, even with esoteric Tags.
Not Sure what youre talking abouz.
But where the analogy with USB-C is very good is that just like USB-C, there is no way for a user to tell from the look of the port or the file extension what the capabilities are. Which even for a fairly tech savvy user like me is frustrating. I have a bunch of cables, some purchased years ago, how do I know what is fit for what?
And now think of the younger generation that has grown up with smartphones and have been trained to not even know what a file is. I remember this story about senior high school students failing their school tests during covid because the school software didn't support heif files and they were changing the file extension to jpg to attempt to convert them.
I have no trust the software ecosystem will adapt. For instance the standard libraries of the .net framework are fossilised in the world of multimedia as of 2008-ish. Don't believe heif is even supported to this day. So that's a whole bunch of code which, unless the developers create workarounds, will never support a newer png format.